U.S. patent application number 10/324283 was filed with the patent office on 2003-06-26 for sample processing device with resealable process chamber.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Bedingham, William, Deeb, Gerald S..
Application Number | 20030118804 10/324283 |
Document ID | / |
Family ID | 32996231 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030118804 |
Kind Code |
A1 |
Bedingham, William ; et
al. |
June 26, 2003 |
Sample processing device with resealable process chamber
Abstract
Devices including resealable film used to define the volume of
one or more process chambers in a sample processing device are
disclosed. The resealable films provide for controlled puncture,
followed by resealing of the puncture site such that the process
chamber remains substantially isolated from the surrounding
environment. The present invention also provides methods of
manufacturing sample processing devices using resealable films, as
well as methods of transferring sample materials into or out of a
process chamber through a resealable film.
Inventors: |
Bedingham, William;
(Woodbury, MN) ; Deeb, Gerald S.; (Mendota
Heights, MN) |
Correspondence
Address: |
Attention: Christopher D. Gram
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
32996231 |
Appl. No.: |
10/324283 |
Filed: |
December 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10324283 |
Dec 19, 2002 |
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09894810 |
Jun 28, 2001 |
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10324283 |
Dec 19, 2002 |
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09847467 |
May 2, 2001 |
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Current U.S.
Class: |
428/301.4 ;
219/388; 428/212; 62/313 |
Current CPC
Class: |
B01L 2300/0803 20130101;
B01L 2400/0683 20130101; B01L 3/50273 20130101; B01L 2300/044
20130101; B01L 2300/0864 20130101; B29D 7/01 20130101; B01L
2200/027 20130101; Y10T 428/24942 20150115; B01L 3/5025 20130101;
G01N 35/00069 20130101; B01L 3/502715 20130101; B01L 2400/0661
20130101; B32B 27/00 20130101; F27D 5/00 20130101; B01L 2300/1861
20130101; B01L 2400/0677 20130101; F27B 9/16 20130101; B01L
2300/0806 20130101; B01L 7/52 20130101; B01L 2300/0887 20130101;
B01L 3/50853 20130101; B01L 2300/0681 20130101; B01L 2300/087
20130101; B01L 2400/0487 20130101; B01L 2300/1822 20130101; B01L
2300/0829 20130101; B01L 3/5027 20130101; B01L 3/502738 20130101;
B01L 2400/0409 20130101; Y10T 428/249952 20150401; B01L 2300/0874
20130101 |
Class at
Publication: |
428/301.4 ;
219/388; 62/313; 428/212 |
International
Class: |
F25D 003/02 |
Claims
1. A sample processing device comprising: a body comprising at
least one process chamber comprising a process chamber volume;
resealable film attached to the body, the resealable film
comprising an internal surface defining a portion of the process
chamber volume and an external surface facing away from the process
chamber volume; and friction modifying material on the external
surface of the resealable film or friction modifying material
incorporated into the resealable film, wherein the incorporated
friction modifying material is chosen because it substantially
migrates to the external surface of the resealable film.
2. The device of claim 1, wherein the friction modifying material
comprises a lubricant.
3. The device of claim 1, wherein the friction modifying material
comprises silicone.
4. The device of claim 1, wherein the friction modifying material
comprises adhesive.
5. The device of claim 1, wherein the resealable film comprises two
outer layers and at least one inner layer forming a core layer
between the two outer layers.
6. The device of claim 5, wherein the core layer comprises
elastomeric material and at least one of the outer layers comprises
plastic material.
7. The device of claim 5, wherein the core layer comprises
elastomeric material and the two outer layers comprise plastic
material.
8. A sample processing device comprising: a body comprising at
least one process chamber comprising a process chamber volume; and
resealable film attached to the body, the resealable film
comprising an internal surface defining a portion of the process
chamber volume and an external surface facing away from the process
chamber volume, wherein the resealable film comprises plastic
material forming a first layer and elastomeric material forming a
second layer attached to the first layer.
9. The device of claim 8, wherein the resealable film comprises a
third layer formed of a plastic material, wherein the second layer
comprises a core layer located between the first layer and the
third layer.
10. A method of manufacturing a sample processing device, the
method comprising: providing a body that comprises at least one
process chamber comprising a process chamber volume; attaching
resealable film to the body, wherein the resealable film comprises
an internal surface defining a portion of the process chamber
volume and an external surface facing away from the process chamber
volume; and providing friction modifying material on the external
surface of the resealable film to provide a targeted level of at
least one of: the friction between the resealable film and a
puncturing object, the flexural rigidity of the resealable film,
the recovering stress of the resealable film, and the elongation at
break of the resealable film.
11. The method of claim 10, wherein the friction modifying material
comprises a lubricant.
12. The method of claim 10, wherein the friction modifying material
comprises silicone.
13. The method of claim 10, wherein the friction modifying material
comprises adhesive.
14. The method of claim 10, wherein the resealable film comprises
two outer layers and at least one inner layer forming a core layer
between the two outer layers.
15. The method of claim 14, wherein the core layer comprises
elastomeric material and at least one of the outer layers comprises
plastic material.
16. The method of claim 14, wherein the core layer comprises
elastomeric material and the two outer layers comprise plastic
material.
17. A method of manufacturing a sample processing device, the
method comprising: providing a body that comprises at least one
process chamber comprising a process chamber volume; attaching
resealable film to the body, wherein the resealable film comprises
an internal surface defining a portion of the process chamber
volume and an external surface facing away from the process chamber
volume; and providing friction modifying material incorporated into
the resealable film, wherein the incorporated friction modifying
material is chosen because it substantially migrates to the
external surface of the resealable film to provide a targeted level
of at least one of: the friction between the resealable film and a
puncturing object, the flexural rigidity of the resealable film,
the recovering stress of the resealable film, and the elongation at
break of the resealable film.
18. The method of claim 17, wherein the friction modifying material
comprises a lubricant.
19. The method of claim 17, wherein the friction modifying material
comprises silicone.
20. The method of claim 17, wherein the friction modifying material
comprises adhesive.
21. The method of claim 17, wherein the resealable film comprises
two outer layers and at least one inner layer forming a core layer
between the two outer layers.
22. The method of claim 17, wherein the core layer comprises
elastomeric material and at least one of the outer layers comprises
plastic material.
23. The method of claim 17, wherein the core layer comprises
elastomeric material and the two outer layers comprise plastic
material.
24. A method of transferring sample material, the method
comprising: providing a sample processing device comprising: a body
that comprises at least one process chamber comprising a process
chamber volume; resealable film attached to the body, the
resealable film comprising an internal surface defining a portion
of the process chamber volume and an external surface facing away
from the process chamber volume; puncturing the resealable film
with a fluid transfer device to form an opening in the resealable
film; inserting the fluid transfer device through the opening in
the resealable film, wherein a portion of the fluid transfer device
is located within the process chamber volume; transferring sample
material into or out of the process chamber using the fluid
transfer device; and removing the fluid transfer device from the
process chamber, wherein the resealable film reseals the opening
after removal of the fluid transfer device.
25. The method of claim 24, wherein the opening comprises a
circumference that is less than 20% of the circumference of the
fluid transfer device.
26. The method of claim 24, wherein the fluid transfer device
comprises a pipette tip.
27. The method of claim 24, wherein the fluid transfer device
comprises a needle.
28. The method of claim 24, wherein the sample material comprises
biological sample material.
29. The method of claim 24, wherein the resealable film comprises
friction modifying material on the external surface of the
resealable film or friction modifying material incorporated into
the resealable film, wherein the incorporated friction modifying
material is chosen because it substantially migrates to the
external surface of the resealable film.
30. The method of claim 29, wherein the friction modifying material
comprises a lubricant.
31. The method of claim 29, wherein the friction modifying material
comprises silicone.
32. The method of claim 29, wherein the friction modifying material
comprises adhesive.
33. The method of claim 29, wherein the resealable film comprises
two outer layers and at least one inner layer forming a core layer
between the two outer layers.
34. The method of claim 33, wherein the core layer comprises
elastomeric material and at least one of the outer layers comprises
plastic material.
35. The method of claim 33, wherein the core layer comprises
elastomeric material and the two outer layers comprise plastic
material.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S.
patent application Ser. No. 09/894,810, filed on Jun. 28, 2001,
titled ENHANCED SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS
(Attorney Docket No. 55266USA7A.002) and a continuation-in-part of
U.S. patent application Ser. No. 09/847,467, filed on May 2, 2001,
titled CONTROLLED-PUNCTURE FILMS (Attorney Docket No. 56322USA6A),
both of which are hereby incorporated by reference in their
respective entireties.
TECHNICAL FIELD
[0002] The present invention relates to devices, methods and
systems for processing of sample materials, such as methods used to
amplify genetic materials, etc.
BACKGROUND
[0003] Many different chemical, biochemical, and other reactions
are sensitive to temperature variations. Examples of thermal
processes in the area of genetic amplification include, but are not
limited to, Polymerase Chain Reaction (PCR), Sanger sequencing,
etc. The reactions may be enhanced or inhibited based on the
temperatures of the materials involved. Although it may be possible
to process samples individually and obtain accurate
sample-to-sample results, individual processing can be
time-consuming and expensive.
[0004] A variety of sample processing devices have been developed
to assist in the reactions described above. A problem common to
many of such devices is that it is desirable to seal the chambers
or wells in which the reactions occur to prevent, e.g.,
contamination of the reaction before, during, and after it is
completed.
[0005] Yet another problem that may be experienced in many of these
approaches is that the volume of sample material may be limited
and/or the cost of the reagents to be used in connection with the
sample materials may also be limited and/or expensive. As a result,
there is a desire to use small volumes of sample materials and
associated reagents. When using small volumes of these materials,
however, additional problems related to the loss of sample material
and/or reagent volume through vaporization, etc. may be experienced
as the sample materials are, e.g., thermally cycled.
SUMMARY OF THE INVENTION
[0006] The present invention provides devices including resealable
film used to close one or more process chambers in a sample
processing device. The resealable films preferably provide for
controlled puncture, followed by resealing of the puncture site
such that the process chamber remains substantially isolated from
the surrounding environment. The present invention also provides
methods for delivering sample materials to a process chamber
through a resealable membrane, as well as removal of materials from
a process chamber through a membrane.
[0007] In those embodiments that include connected process chambers
in which different processes may be sequentially performed on a
starting sample, the present invention may provide an integrated
solution to the need for obtaining a desired finished product from
a starting sample even though multiple processes are required to
obtain the finished product.
[0008] In other embodiments in which the process chambers are
multiplexed from a loading chamber (in which the starting sample is
loaded), it may be possible to obtain multiple finished samples
from a single starting sample. Those multiple finished samples may
be the same materials where the multiplexed process chambers are
designed to provide the same finished samples. Alternatively, the
multiple finished samples may be different samples that are
obtained from a single starting sample.
[0009] As used herein, "elongation at break of the film" refers to
the tensile strain at break as determined by ASTM standard
D822.
[0010] As used herein, "film" refers to a flexible article having
any shape that has two major surfaces, e.g., sheet or tube.
Optionally the film has more than one layer. The film may
preferably have, e.g., a total thickness of no more than about 400
micrometers (0.016 inches), more preferably no more than about 250
micrometers (0.010 inches) depending on the materials and
construction used.
[0011] As used herein, "flexural rigidity of the film" refers to
the product of the modulus of elasticity and moment of inertia of a
film.
[0012] As used herein, "load" refers to the mechanical force that
is applied to a body.
[0013] As used herein, "modulus of elasticity of the film" refers
to the amount of force necessary to deform the film one strain
unit.
[0014] As used herein, "moment of inertia of the film" refers to
the geometric stiffness of the film (i.e., the cube of the
thickness divided by 12).
[0015] As used herein "puncturability" refers to the displacement
to break when the load of a probe is applied to a film.
[0016] As used herein, "rescalability" refers to the ability of a
film to reduce the size of an opening in the film at a puncture
site up to the point of completely closing the puncture site. In
embodiments where resealability is desired, preferably, an opening
that is created in the film by a puncturing object reseals such
that the circumference of the opening is less than 50% of the
circumference of the puncturing object. More preferably, the
opening will decrease to less than 20% of the circumference of the
puncturing object.
[0017] As used herein, "sealability" refers to the ability of a
film to form a seal around a puncturing object while it is
puncturing the film.
[0018] As used herein, "recovering stress of the film" refers to
the difference between the film's tensile stress at 300% elongation
as determined by ASTM standard D822 and the stress when the film is
returned to its original length after stretching to 300%
elongation.
[0019] As used herein, "surface friction between the film and a
puncturing object" refers to the linear coefficient expressing the
tangential force to pull a sled covered with that film over a track
consisting of the material of the puncturing object compared to the
normal force (weight) of the sled.
[0020] In one aspect, the present invention provides a sample
processing device including a body with at least one process
chamber having a process chamber volume; resealable film attached
to the body, the resealable film having an internal surface
defining a portion of the process chamber volume and an external
surface facing away from the process chamber volume; and friction
modifying material on the external surface of the resealable film
or friction modifying material incorporated into the resealable
film, wherein the incorporated friction modifying material is
chosen because it substantially migrates to the external surface of
the resealable film.
[0021] In another aspect, the present invention provides a sample
processing device including a body with at least one process
chamber having a process chamber volume; resealable film attached
to the body, the resealable film having an internal surface
defining a portion of the process chamber volume and an external
surface facing away from the process chamber volume, wherein the
resealable film includes plastic material forming a first layer and
elastomeric material forming a second layer attached to the first
layer.
[0022] In another aspect, the present invention provides a method
of manufacturing a sample processing device, the method including
providing a body that includes at least one process chamber with a
process chamber volume; attaching resealable film to the body,
wherein the resealable film has an internal surface defining a
portion of the process chamber volume and an external surface
facing away from the process chamber volume; providing friction
modifying material on the external surface of the resealable film
to provide a targeted level of at least one of: the friction
between the resealable film and a puncturing object, the flexural
rigidity of the resealable film, the recovering stress of the
resealable film, and the elongation at break of the resealable
film.
[0023] In another aspect, the present invention provides a method
of manufacturing a sample processing device by providing a body
having at least one process chamber with a process chamber volume;
attaching resealable film to the body, wherein the resealable film
has an internal surface defining a portion of the process chamber
volume and an external surface facing away from the process chamber
volume; providing friction modifying material incorporated into the
resealable film, wherein the incorporated friction modifying
material is chosen because it substantially migrates to the
external surface of the resealable film to provide a targeted level
of at least one of: the friction between the resealable film and a
puncturing object, the flexural rigidity of the resealable film,
the recovering stress of the resealable film, and the elongation at
break of the resealable film.
[0024] In another aspect, the present invention provides a method
of transferring sample material by providing a sample processing
device including a body with at least one process chamber having a
process chamber volume; resealable film attached to the body, the
resealable film having an internal surface defining a portion of
the process chamber volume and an external surface facing away from
the process chamber volume. The method further includes puncturing
the resealable film with a fluid transfer device to form an opening
in the resealable film; inserting the fluid transfer device through
the opening in the resealable film, wherein a portion of the fluid
transfer device is located within the process chamber volume;
transferring sample material into or out of the process chamber
using the fluid transfer device; and removing the fluid transfer
device from the process chamber, wherein the resealable film
reseals the opening after removal of the fluid transfer device.
[0025] These and other features and advantages of the devices,
systems and methods of the invention are described below with
respect to illustrative embodiments of the invention.
BRIEF DESCRIPTION OF THE FIGURES
[0026] FIG. 1 is a top plan view of one device according to the
present invention.
[0027] FIG. 2 is an enlarged partial cross-sectional view of a
process chamber in the device of FIG. 1.
[0028] FIG. 3 is an enlarged partial cross-sectional view of the
process chamber with a fluid transfer device inserted into the
process chamber through a resealable film.
[0029] FIG. 4 is an enlarged partial cross-sectional view of the
process chamber after removal of the fluid transfer device from the
process chamber.
[0030] FIG. 5 depicts an apparatus used to drive a puncturing
object into a film and measure the flexure at rupture or break of
the film.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE
INVENTION
[0031] The present invention provides a device that can be used in
methods that involve thermal processing, e.g., sensitive chemical
processes such as PCR amplification, ligase chain reaction (LCR),
self-sustaining sequence replication, enzyme kinetic studies,
homogeneous ligand binding assays, and more complex biochemical or
other processes that require precise thermal control and/or rapid
thermal variations.
[0032] Although one illustrative embodiment of a device is
described below, sample processing devices according to the
principles of the present invention may be manufactured according
to the principles described in U.S. Provisional Patent Application
Serial No. 60/214,508 filed on Jun. 28, 2000 and titled THERMAL
PROCESSING DEVICES AND METHODS (Attorney Docket No.
55265USA19.003); U.S. Provisional Patent Application Serial No.
60/214,642 filed on Jun. 28, 2000 and titled SAMPLE PROCESSING
DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 55266USA99.003);
U.S. Provisional Patent Application Serial No. 60/237,072 filed on
Oct. 2, 2000 and titled SAMPLE PROCESSING DEVICES, SYSTEMS AND
METHODS (Attorney Docket No. 56047USA29); and U.S. Provisional
Patent Application Serial No. 60/284,637 filed on Apr. 18, 2001 and
titled ENHANCED SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS
(Attorney Docket No. 56546USA49.002). Other potential device
constructions may be found in, e.g., U.S. patent application Ser.
No. 09/710,184 filed on Nov. 10, 2000 and titled CENTRIFUGAL
FILLING OF SAMPLE PROCESSING DEVICES (Attorney Docket No.
55265USA9A) and U.S. Provisional Patent Application Serial No.
60/260,063 filed on Jan. 6, 2001 and titled SAMPLE PROCESSING
DEVICES, SYSTEMS AND METHODS (Attorney Docket No. 56284USA19.002).
Still other constructions may be described in U.S. patent
application Ser. No. 09/894,810, filed on Jun. 28, 2001, titled
ENHANCED SAMPLE PROCESSING DEVICES, SYSTEMS AND METHODS (Attorney
Docket No. 55266USA7A.002).
[0033] Although relative positional terms such as "top" and
"bottom" may be used in connection with the present invention, it
should be understood that those terms are used in their relative
sense only. For example, when used in connection with the devices
of the present invention, "top" and "bottom" are used to signify
opposing sides of the devices. In actual use, elements described as
"top" or "bottom" may be found in any orientation or location and
should not be considered as limiting the methods, systems, and
devices to any particular orientation or location. For example, the
top surface of the device may actually be located below the bottom
surface of the device in use (although it would still be found on
the opposite side of the device from the bottom surface).
[0034] One illustrative device manufactured according to the
principles of the present invention is depicted in FIGS. 1 and 2.
The device 10 may be in the shape of a circular disc as illustrated
in FIG. 1, although any other shape could be used. The depicted
device 10 includes a plurality of process chambers 50, each of
which defines a volume for containing a sample and any other
materials that are to be processed with the sample.
[0035] The illustrated device 10 includes ninety-six process
chambers 50, although it will be understood that the exact number
of process chambers provided in connection with a device
-manufactured according to the present invention may be greater
than or less than ninety-six, as desired.
[0036] The process chambers 50 in the illustrative device 10 are in
the form of chambers, although the process chambers in devices of
the present invention may be provided in the form of capillaries,
passageways, channels, grooves, or any other suitably defined
volume.
[0037] Although the depicted device relies on centrifugal forces
and distribution channels to move materials into the various
process chambers, it should be understood that any sample
processing device used in connection with the present may or may
not include distribution channels or other fluid movement
structures. Rather, the sample processing devices of the present
invention may include a number of completely isolated and separate
process chambers into which materials are delivered and from which
materials are removed independent of the other process chambers.
For example, the present invention may include conventional
microtiter plates and other sample processing devices including one
or more independent, isolated process chambers.
[0038] The device 10 of FIGS. 1 and 2 is a multi-layered composite
structure including a substrate 20, first layer 30, and a
resealable film 40. It is preferred that the substrate 20, first
layer 30 and resealable film 40 of the device 10 be attached or
bonded together with sufficient strength to resist any expansive
forces that may develop within the process chambers 50 as, e.g.,
the constituents located therein are rapidly heated during thermal
processing. The robustness of the bonds between the components may
be particularly important if the device 10 is to be used for
thermal cycling processes, e.g., PCR amplification. The repetitive
heating and cooling involved in such thermal cycling may pose more
severe demands on the bond between the sides of the device 10.
Another potential issue addressed by a more robust bond between the
components is any difference in the coefficients of thermal
expansion of the different materials used to manufacture the
components.
[0039] The process chambers 50 in the depicted device 10 are in
fluid communication with distribution channels 60 that, together
with loading chamber 62, provide a distribution system for
distributing samples to the process chambers 50. Introduction of
samples into the device 10 through the loading chamber 62 may be
accomplished by rotating the device 10 about a central axis of
rotation such that the sample materials are moved outwardly due to
centrifugal forces generated during rotation. Before the device 10
is rotated, the sample can be introduced into the loading chamber
62 for delivery to the process chambers 50 through distribution
channels 60. The process chambers 50 and/or distribution channels
60 may include ports through which air can escape and/or other
features to assist in distribution of the sample materials to the
process chambers 50. Alternatively, sample materials could be
loaded into the process chambers 50 under the assistance of vacuum
or pressure.
[0040] The illustrated device 10 includes a loading chamber 62 with
two subchambers 64 that are isolated from each other. As a result,
a different sample can be introduced into each subchamber 64 for
loading into the process chambers 50 that are in fluid
communication with the respective subchamber 64 of the loading
chamber 62 through distribution channels 60. It will be understood
that the loading chamber 62 may contain only one chamber or that
any desired number of subchambers 64, i.e., two or more subchambers
64, could be provided in connection with the device 10.
[0041] FIG. 2 is an enlarged cross-sectional view of a portion of
the device 10 including one of the process chambers 50. The
substrate 20 includes a first major side 22 and a second major side
24. Each of the process chambers 50 is formed, at least in part in
this embodiment, by a void 26 formed through the substrate 20. The
illustrated void 26 is formed through the first and second major
sides 22 and 24 of the substrate 20.
[0042] The substrate 20 may preferably be polymeric, but may be
made of other materials such as glass, silicon, quartz, ceramics,
etc. Furthermore, although the substrate 20 is depicted as a
homogenous, one-piece integral body, it may alternatively be
provided as a non-homogenous body of, e.g., layers of the same or
different materials. For those devices 10 in which the substrate 20
will be in direct contact with the sample materials, it may be
preferred that the material or materials used for the substrate 20
be non-reactive with the sample materials. Examples of some
suitable polymeric materials that could be used for the substrate
in many different bioanalytical applications may include, but are
not limited to, polycarbonate, polypropylene (e.g., isotactic
polypropylene), polyethylene, polyester, etc.
[0043] A first layer 30 is provided on one side of the substrate 20
in the illustrated embodiment. Although the first layer 30 is
depicted as a homogenous, one-piece integral layer, it may
alternatively be provided as a non-homogenous layer of, e.g.,
sub-layers of the same or different materials, e.g., polymeric
materials, metallic layers, etc. Also, in some embodiments, the
process chamber 50 may be formed as a depression in the substrate
20 with no first layer 30 required to define the volume of the
process chamber 50.
[0044] A resealable film 40 is provided on the opposite side of the
substrate 20 to define the remainder of the volume of the process
chamber 50. Although the resealable film 40 is depicted as a
homogenous, one-piece integral layer, it may alternatively be
provided as a non-homogenous layer of, e.g., sub-layers of the same
or different materials, e.g., polymeric materials, etc. The
resealable film 40 includes an external surface 42 facing away from
the volume of the process chamber 50 and an internal surface 44
facing the volume of the process chamber 50.
[0045] It may be preferred that at least a portion of the materials
defining the volume of the process chamber 50 be transmissive to
electromagnetic energy of selected wavelengths. In the depicted
device 10, if the body 20, first layer 30, and/or resealable film
40 may be transmissive to electromagnetic energy of selected
wavelengths.
[0046] The selected wavelengths may be determined by a variety of
factors, for example, electromagnetic energy designed to heat
and/or interrogate a sample in the process chamber 50,
electromagnetic energy emitted by the sample (e.g., fluorescence),
etc. By providing a transmissive process chamber 50, a sample in
the chamber can be interrogated by electromagnetic energy of
selected wavelengths (if desired) and/or electromagnetic energy of
the selected wavelengths emanating from the sample can be
transmitted out of the process chamber 50 where it can be detected
by suitable techniques and equipment. For example, electromagnetic
energy may be emitted spontaneously or in response to external
excitation. A transmissive process chamber 50 may also be monitored
using other detection techniques, such as color changes or other
indicators of activity or changes within the process chambers
50.
[0047] In some instances, however, it may be desirable to prevent
the transmission of selected wavelengths of electromagnetic energy
into the process chambers. For example, it may be preferred to
prevent the transmission of electromagnetic energy in the
ultraviolet spectrum into the process chamber where that energy may
adversely impact any reagents, sample materials, etc. located
within the process chamber.
[0048] Also depicted in FIG. 2 is sample material 52 located within
the volume of the process chamber 50. The sample material may
include at least one fluid component, preferably a liquid.
Furthermore, the sample material may be a biological sample
material.
[0049] FIG. 3 is an enlarged partial cross-sectional view of the
process chamber of FIG. 2 after insertion of a fluid transfer
device 70 into the volume of the process chamber 50 through the
resealable film 40. The fluid transfer device 70 may be, e.g., a
pipette, needle, or other device capable of taking up and/or
delivering fluids. In addition, the fluid transfer device 70 may
preferably have sufficient structural rigidity to pierce the
resealable film 40 by itself. Alternatively, the fluid transfer
device 70 may be inserted through an opening already pierced by
another instrument. The fluid transfer device 70 may have a sharp
tip 72 as shown or the tip may be blunt depending on the properties
of the resealable film 40 and the fluid transfer device itself.
[0050] FIG. 4 is an enlarged partial cross-sectional view of the
process chamber of FIGS. 2 & 3 after removal of the fluid
transfer device 70 from the volume of the process chamber 50. In
the depicted embodiment, a portion of the sample material 52 in the
process chamber 50 has been removed using the fluid transfer device
70 (although as discussed above, the fluid transfer device 70 may
also deliver materials into the process chamber 50).
[0051] The opening 46 through which the fluid transfer device 70
entered and exited the process chamber includes an perforation in
the resealable film 40 that reseals upon removal of the fluid
transfer device 70. While the materials used for resealable film 40
exhibit resealability of the opening 46 upon removal of a fluid
transfer device as depicted in FIG. 4, the resealable film 40 may
also preferably exhibit sealability when the fluid transfer device
70 is inserted through the layer 40.
[0052] The resealable film 40 may be attached to the body 20 around
at least the boundaries of the process chamber 50 to seal the
sample materials 52 therein. Any suitable technique or combination
of techniques may be used to attach the resealable film 40 to the
body 20. Examples of some suitable attachment techniques include,
but are not limited to, adhesives (e.g., pressure sensitive,
hot-melt, curable, etc.), thermal welding, ultrasonic welding, heat
sealing, chemical welding, clamping, mechanical fasteners, etc.
[0053] The resealable film 40 may preferably be a polymeric film,
preferably a polymeric film that can be controllably punctured and
optionally sealed and/or resealed. Typically, these properties are
determined by at least one of flexural lo rigidity of the film, the
elongation at break of the film, the recovering stress of the film,
and friction between the film and a puncturing object.
[0054] Control over puncturability in a resealable film 40 can be
accomplished by modifying a surface of the film to provide desired
levels of flexural rigidity of the film, the elongation at break of
the film, the recovering stress of the film, and surface friction
between the film and the puncturing object, e.g., a fluid transfer
device 70.
[0055] Modifying the surface can be accomplished by a number of
methods. For example, it can include changing the modulus of the
film by altering the temperature of the film prior to, and during,
the penetration by a puncturing object; stretching and optionally
releasing the film prior to penetration by a puncturing object;
applying a modifying material to the surface of the film; or adding
a modifying material to the bulk material comprising a film. For
multi-layer films, modifying can also include changing the
thickness of one or more layers or changing the properties of the
surface layer that first contacts a puncturing object.
[0056] Another option is to modify the coefficient of friction
between the puncturing object and the film (hereafter COF) to
control the puncture resistance of the films. A puncturing object
and flexible film generally interact as follows: as the puncturing
object makes contact with the film, the film deforms in the
direction of the puncturing object's motion. This is accompanied by
local stretching of the film in the vicinity of the puncturing
object's tip.
[0057] As the film stretches, the elasticity of the film's
materials requires the film construction to exert a hoop
(compressive radially inward) stress on the puncturing object. This
force is exerted nearly normal to the lateral surface of the
puncturing object. Simultaneously, there is a tangential, or
surface, force associated with driving the puncturing object
downward and perpendicular to the force exerted by the hoop stress
of the film.
[0058] If the COF is high (i.e., the puncturing object adheres to
the film surface) the tangential stress associated with driving the
puncturing object down into the film will not be great enough to
overcome the normal force from the film hoop stress holding the
film against the puncturing object (i.e., the product of the COF
and the normal force is greater than the tangential force). Thus,
the puncturing object will pull the surrounding film downward with
it such that the force exerted by the object will be distributed
over the entire film surface in contact with the object.
[0059] Because the film in contact with the puncturing object does
not experience a stress large enough to cause mechanical failure,
the portion of the film not in contact with the puncturing object
will also be strained as the film in contact with the object is
pulled with the movement of the puncturing object. This deformation
of the non-contacting film will effectively distribute the load of
the puncturing object so that mechanical failure will only be
caused at much larger displacements, i.e., large film
deformations.
[0060] Conversely, if the COF is low, the tangential force from the
puncturing object will overcome the normal force and the object
will slip against the film surface. This will allow the load of the
puncturing object to be concentrated entirely at its tip thus
causing greater distortion of the film material underneath the
object's tip until the object punctures (i.e., mechanically
ruptures) the film. Thus, one may control the ease of puncture in
flexible films by controlling the COF.
[0061] Additionally, changing the moment of inertia of a film can
control puncture in films. A stiff film is more easily punctured
than a flexible film. As has been explained, as a puncturing object
makes contact with a film, the area immediately underneath the
puncturing object undergoes distortion and stretching. This causes
the film to exert a hoop stress inward to make contact (or conform
around) the puncturing object.
[0062] However, this ability to make contact around the puncturing
object depends on the ability of the film itself to conform to the
object. For example, with a three-layered film of an elastomeric
core layer and relatively rigid outer layers, as the film is
stretched under the tip of the puncturing object, the elastomeric
core layer exerts a force generated by the tendency of the film to
recover from the hoop stress to drive the film toward contact with
the object. If the outer layer is not rigid (due to small moment of
inertia, or low modulus of elasticity of the film) in comparison to
the core layer then the core layer material can drive the entire
film to contact the puncturing object. However, if the outer layer
is thick or stiff, then the core layer will be less able to force
the entire film to conform to the puncturing object. The extent of
the ability of the film to conform to the puncturing object also
controls puncture resistance. If the film cannot conform to the
puncturing object surface then the object will be able to
concentrate its entire load immediately below its tip regardless of
the COF. Conversely, if the film can conform to the puncturing
object 25 surface then puncture may be impeded, if the COF is
sufficiently high.
[0063] When films having at least two layers are used in connection
with the present invention, changing the recovering stress of the
layer that is not first contacted by a puncturing object influences
puncturability because it is this force that drives the contact of
the surface of the film with the puncturing object. The surface of
a material with a lower recovery stress will be less driven to
contact the puncturing object, thereby allowing puncture to occur
more easily.
[0064] The puncture resistance of some film constructions can be
affected by the recovery stress of the film even when the
elongation at break of each of the layers of the film is
substantially unchanged.
[0065] The films of the present invention preferably include
elastomeric layers in a manner that results in a resealable film.
As was discussed in regard to puncture resistance, elastomeric
films exert high hoop stresses, i.e., recovering forces from
cylindrical deformation, (because they try to return to their
original, unstressed state). It is this inward (toward the
puncturing object) force that facilitates resealing. The tendency
of less elastic films to generate the restoring force to reseal or
recover strain in response to deformation is greatly reduced in
comparison to elastomeric films.
[0066] It has been found that there is a correlation between case
of puncture and the ability of the film to reseal. If the film
punctures easily, then only the perimeter of a relatively small
area of the film (the area in contact with the tip of the
puncturing object) is stretched to break. Depending on the size of
the puncturing object, this can be a relatively small area and the
resulting opening will be small. However, if the film is
puncture-resistant, the ability of the film to conform to the
puncturing object will be increased such that the area of the film
in contact with the puncturing object will cover not only the
object's tip but also at least some of the lateral surfaces of the
object. Accordingly, the perimeter of the area that is stressed to
break will include at least the portion of film in contact with the
lateral surface of the object.
[0067] Thus, for films with high COFs, the opening (the area within
the broken perimeter) is relatively large and the film is less able
to reseal the opening depending on the size and shape of the
puncturing object. Thus, the resealability of openings in the films
may be controlled in tandem with (though not independent of) the
puncture resistance of the films.
[0068] Elastomeric layers also contribute to the ability of a film
to seal around a puncturing object. The elastic recovery of a film
also allows the film to conform to the shape of the puncturing
object. This sealability property is advantageous when it is
desirable to isolate a process chamber from a surrounding
environment while a film is being punctured. For example,
sealability allows a film to be punctured without allowing
contaminants or other materials to pass through the puncture
site.
[0069] In one embodiment, the resealable is a polymeric multilayer
film of two outer layers and at least one inner layer. Modifying
such a multilayer film can involve modifying at least one of the
outer layers of the film to provide a targeted level of at least
one of flexural rigidity of the film, the elongation at break of
the film, the recovering stress of the film, and the friction
between the film and a puncturing object. For example, the
thickness and/or stiffness of an outer layer can be changed to make
an overall change in the thickness or stiffness of a film.
Alternatively, modifying such a multilayer film can involve
modifying an inner layer of the film to provide a targeted level of
flexural rigidity of the film and elongation at break of the
film.
[0070] In general, films having an (AB).sub.nA (where n is greater
than 1) construction can be more flexible than films of equal
thickness having an ABA construction. This occurs, for example,
when the A layer is a hard stiff material and the B material is a
soft, pliable material. When a film is flexed the material at one
surface is compressed and the material at the opposing surface is
stretched. The material in the middle of the film is not
significantly compressed or stretched. If the stiff material is at
or near the film's surface and the soft material is near the film's
center, stretching the film requires more force than if the stiff
material were near the film's center and the soft material were at
the surfaces.
[0071] However, in a film having, e.g., an ABABABA structure with
the same relative amounts of A and B as an ABA film of equal
thickness, some of the soft material has been moved out toward the
surfaces where the stretching and compression occur during flexing,
and some of the stiff material has been moved toward the center of
the film where there is minimal stretching and compression. This
structure makes it easier to bend the film because less of the
stiff material needs to be stretched or compressed.
[0072] Nevertheless, if you pull the film in tension (parallel to
the layers) the stiffness of the film should be the same as for the
ABA film because the same amount of A and B material is in cross
section.
[0073] In one embodiment of the present invention, controlling the
puncturability, resealability, and, optionally, sealability of a
puncture site in a polymeric film can be accomplished by producing
a polymeric film having at least two layers wherein a first layer
includes a plastic material and a second layer includes an
elastomeric material. In this embodiment, the type and amount of
materials of the first layer and second layer are selected to
impart specified levels of flexural rigidity of the film, the
elongation at break of the film, the recovering stress of the film,
and friction between the film and a puncturing object.
[0074] In another embodiment, controlling the puncturability,
resealability, and, optionally, sealability of a puncture site in a
polymeric film can be accomplished by: selecting a polymeric
material and a modifying material; combining the polymeric material
and the modifying material to form a molten mixture; and forming
the molten mixture into a film; wherein the type, and amount of
polymeric and modifying materials 0 are selected to provide a
targeted level of at least one of flexural rigidity of the film,
the elongation at break of the film, the recovering stress of the
film, and the friction between the film and a puncturing
object.
[0075] Whether it is applied to a surface of a polymeric film or
mixed into the polymeric film, the modifying material can be a
variety of materials able to change at least one of flexural
rigidity of the film, the elongation at break of the film, the
recovering stress of the film, or the friction between the film and
puncturing object, such as a lubricant, an adhesive, or other
monomers, oligomers, or polymers. Examples of modifying materials
that can enhance puncturability include silicone oil and a wide
variety of thermoplastic materials having a low COF relative to the
puncturing object.
[0076] For example, a high density polyethylene film would be an
appropriate puncturable film if the puncturing object were a
polypropylene needle. Examples of modifying materials that enhance
puncture resistance are elastomers resulting in relatively high
COFs such as, for example, tackified elastomers or self-tacky
elastomers. The modifying material may be selected for its ability
to slide against a specific puncturing object, thereby contributing
to the resealability of the puncture site by causing a small
diameter opening to be formed. The more puncturable a film is, the
better it is able to reseal because the force and effect of the
puncturing object is concentrated in a small area.
[0077] As mentioned above, the polymeric film can include one or
more layers. For example, the polymeric film can include three
layers--two outer layers and a core layer. In such a three-layer
construction, the desired degree of puncture resistance and ability
to seal and reseal can be affected by adjusting the properties of
the film's core layers or at least one of the film's outer layers
rigidity.
[0078] Plastic materials suitable for use in the present invention
include those that are capable of being formed into a film layer,
have a modulus of elasticity over 108 Pa, and cannot sustain more
than 20% strain without incurring permanent set (i.e., permanent
deformation) at ambient temperature. Examples of suitable plastic
materials include thermoplastics such as polyethylenes (high
density, low density, and very low density), polypropylene,
polymethylmethacrylate, polyethylene terephthalate, polyamides, and
polystyrene; thermosets such as dyglycidyl esters of bisphenol A
epoxy resins, lo bisphenol A dicyanate esters, orthophthalic
unsaturated polyesters, bisphenol A vinyl esters.
[0079] Elastomeric materials suitable for use in the present
invention can include any material that is capable of being formed
into a thin film layer and exhibits elastomeric properties at
ambient conditions. Elastomeric means that the material will
substantially resume its original shape after being stretched.
Further, preferably, the elastomer will sustain only small
permanent set following deformation and relaxation which set is
preferably less than 20% and preferably less than 10% at moderate
elongation, e.g., about 400-500%. Generally any elastomer is
acceptable which is capable of being stretched to a degree that
causes relatively consistent permanent deformation in a plastic
outer layer. This can be as low as 50% elongation. Preferably,
however the elastomer is capable of undergoing up to 300 to 1200%
elongation at room temperature, and most preferably 600 to 800%
elongation at room temperature. The elastomer can be pure elastomer
or blends with an elastomeric phase or content that will exhibit
substantial elastomeric properties at room temperature.
[0080] Examples of suitable elastomeric materials include natural
or synthetic rubbers block copolymers that are elastomeric, such as
those known to those skilled in the art as A-B or A-B-A block
copolymers. Such copolymers are described for example on U.S. Pat.
Nos. 3,265,765; 3,562,356; 3,700,633; 4,116,917, and 4,156,673.
Useful elastomeric compositions include, for example,
styrene/isoprene/styrene (SIS) block 30 copolymers, elastomeric
polyurethanes, ethylene copolymers such as ethylene vinyl acetates,
ethylene/propylene monomer copolymer elastomers or
ethylene/propylene/diene terpolymer elastomers. Blends of these
elastomers with each other or with modifying non-elastomers are
also contemplated. For example, up to 50 weight %, but preferably
less than 30 weight %, of polymers can be added as stiffening aids
such as polyvinylstyrenes such as polyalphamethyl styrene,
polyesters, epoxies, 5 polyolefins, e.g., polyethylene or certain
ethylene/vinyl acetates, preferably those of higher molecular
weight, or coumarone-indene resin.
[0081] In a multi-layer film, the plastic layer can be an outer or
inner layer (e.g., sandwiched between two elastomeric layers). In
either case, it will modify the elastic properties of the
multilayer film.
[0082] Recovery of a multilayer film after puncture will depend on
a number of factors such as the nature of the elastomeric layer,
the nature of the plastic layer, the manner in which the film is
stretched, and the relative thickness of the elastomeric and
plastic layers. Percent recovery (with no load is on the film)
refers to stretched length minus the recovered length, the sum of
which is divided by the original length.
[0083] Generally, the plastic layer will hinder the elastic force
with a counteracting resisting force. A plastic outer layer will
not stretch with an inner elastomeric layer after the film has been
stretched (provided that the second stretching is less than the
first), the plastic outer layer will just unfold into a rigid
sheet. This reinforces the core layer, resisting or hindering the
contraction of the elastomeric core layer.
[0084] For obtaining a more puncturable film, the friction between
a puncturing object and the surface of the film should be reduced.
A wide variety of mechanisms can be used to reduce this friction as
long as there is a concentration of stress at the point of load
applied by the object. This can include applying a modifying
material to the film surface or selecting a different material for
the outer surface of the film such that the coefficient of friction
between the puncturing object and film surface is reduced. For
example, a polypropylene/styrene-isopren- e synthetic
rubber/polypropylene multi layer film can be made more puncturable
by a polypropylene tip if the film surface is sprayed with silicone
oil.
[0085] Puncturability may be increased by stretching a film.
Holding a film in a 30 stretched position can make it more
puncturable because it is less able to conform to the puncturing
object.
[0086] In contrast, stretching and releasing a multilayer film
comprising both elastomeric and plastic layers can decrease
puncturability by decreasing the film's flexural rigidity. This can
be done by stretching the multilayer film past the elastic limit of
the plastic layer(s). Stretching and releasing can also lower a
multilayer film's s coefficient of friction and modulus of
elasticity. In some embodiments, the plastic layer can function to
permit controlled release or recovery of the stretched elastomeric
layer, modify the modulus of elasticity of the multilayer film
and/or stabilize the shape of the multilayer film.
[0087] The present invention provides polymeric films, including
single films with a modified surface, having varying degrees of
puncturability, resealability, and, optionally varying degrees of
sealability with regard to the shape of a specific type of
puncturing object, e.g., a fluid transfer device. In one
embodiment, the film can be punctured when the film is stretched to
a given displacement by a puncturing object applied to a first
major surface, but the film cannot be punctured when the film is
stretched to the same displacement by the same puncturing object
applied to a second opposing major surface. For example a two-layer
film having a low COF on the first major surface and a high COF on
the second would be more easily punctured by a puncturing object
through the first surface than through the second surface. Of
course, the shape of the tip of a puncturing object can also affect
the puncturability of the film.
[0088] The single layer films of the present invention may be made
by extrusion methods or any other suitable methods known in the
art.
[0089] The multilayer films of the present invention may be formed
by any convenient layer forming process such as coating,
lamination, coextruding layers or stepwise extrusion of layers, but
coextrusion is preferred. Coextrusion per se is know and is
described, for example, in U.S. Pat. Nos. 3,557,265 and 3,479,425.
The layers are typically coextruded through a specialized feedblock
or a specialized die that will bring the diverse materials into
contact while forming the film.
[0090] Coextrusion may be carried out with multilayer feedblocks or
dies, for example, a three-layer feedblock (fed to a die) or a
three-layer die such as those made by Cloeren 30 Co., Orange, Tex.
A suitable feedblock is described in U.S. Pat. No. 4,152,387.
Typically streams of materials flowing out of extruders at
different viscosities are separately introduced into the feedblock
and converge to form a film. A suitable die is described in U.S.
Pat. No. 6,203,742.
[0091] The feedblock and die used are typically heated to
facilitate polymer flow and layer adhesion. The temperature of the
die depends on the polymers used. Whether the film is prepared by
coating, lamination, sequential extrusion, coextrusion, or a
combination thereof, the film formed and its layers will preferably
have substantially uniform thicknesses across the film.
[0092] The present invention also provides systems of puncturable,
resealable films and puncturing objects (e.g., fluid transfer
devices) that can be tailored to each other to obtain a desired
level of puncturability. For example, if a specific fluid transfer
device is to be used as a puncturing object, the properties and
characteristics of a film can be made to complement the puncturing
object to provide the desired level of ease of puncturability. The
fluid transfer device may be made of a particular material, may
have a particular shape (including the shape of its tip), etc.
Knowing this information, the composition and structure of a film
can be made to provide the appropriate flexural rigidity of the
film, the elongation at break of the film, the recovering stress of
the film, and friction between the film and puncturing object to
provide the desired level of ease of puncturability of the film.
Optionally, sealability and resealability of the film can be
tailored in the same manner.
[0093] Conversely, if a given film is to be punctured, based on its
composition, structure, flexural rigidity, elongation at break, and
recovering stress, a puncturing object can be chosen based on its
composition (which will affect the friction between the film and
puncturing object), and its shape (including the shape of its tip),
to provide the desired level of ease of puncturability,
resealability, and, optionally, sealability of the film. Specific
examples of the methods of this invention as well as objects and
advantages of this invention are further illustrated by the
following examples, but the particular materials and amounts
thereof recited in these examples, as well as other conditions and
details, should not be construed to unduly limit this
invention.
Test Methods
[0094] Puncture Resistance Test
[0095] Film samples were tested for puncture resistance using two
variations of ASTM D3763-97a in which apparatus 110 illustrated in
FIG. 5 was used to drive a puncturing object into a film and
measure the flexure at rupture or break. In Variation A, opening
112 in the center of clamp assembly 114 of the test apparatus had a
diameter of 25 mm and the puncturing object 116 was a metal plunger
with a fixture holding a 10 microliter (AL) polypropylene plastic
pipette (available from Eppendorf, Germany).
[0096] The pipette has a tip with an outside diameter of 0.84 mm
and a shaft that tapered over a length of 5 mm to a substantially
constant diameter of about 2 mm. In Variation B, hole 112 in the
center of clamp assembly 114 of the test apparatus had a diameter
of 76 mm. The puncturing object 116 was a smooth cylindrical metal
probe having a hemispherical tip with a diameter of about 12 mm.
The speed of the probe was 508 mm/min. The amount of deflection,
i.e., displacement at peak load prior to rupture was measured in
inches and converted into millimeters. Each reported value is an
average of 5 test measurements.
[0097] Dynamic Coefficient of Friction Test
[0098] The dynamic coefficient of friction of the surface of the
film sample that would first contact a puncturing object was
determined by using ASTM D1894-95 with the apparatus described in
drawing c, FIG. 1 of the ASTM and the sled as described in Section
5.1 of the ASTM. The sliding surface was a sheet of cast
polypropylene film (available as7C12N from Shell Chemical Co.,
Beaupre, Ohio). A metal filament wire was used to pull the sled and
various weights were placed on the sled to achieve different forces
normal to the plane of the sample being tested. The normal force
was calculated as the mass of the weight on the sled multiplied by
the gravitational acceleration. The steady-state pulling force was
determined, after initial transient values, for each normal force
and was plotted against the normal force. The dynamic coefficient
was the slope of the curve of the plotted data.
[0099] Opening Dimension Measurement
[0100] To determine this measurement, a punctured opening was
viewed with a Boeckeler VIA-170 microscope (Tuscon, Ariz.) using
50.times.and 200.times.objective lenses. The dimensions were
measured with a Moritex Scopeman (Model MS803, San Diego, Calif.)
and the data was converted to an area measurement. Each reported
value represents the average of three measurements.
EXAMPLES
Example 1
[0101] Example 1 illustrates the effect of the dynamic coefficient
of friction of a film on the puncture resistance and resealability
of a multilayer film.
[0102] Sample A was a three layer film with a thermoplastic
elastomer core layer and high density polyethylene (HDPE) outer
layers. The outer layers were made of thermoplastic HDPE A
(available as PETROTHENE LS3150-00, elongation percent at break of
300, Equistar Chemicals, Houston, Tex.). The outer layer material
was conveyed through an extruder having multiple zones with a
single screw extruder (diameter of 19 mm, L/D of 32/1, available
from Killion, Inc., Cedar Grove, N.J.). The outer layer material
extruder operated with zone temperatures increasing from
163.degree. C. to 216.degree. C. The outer layer material was
conveyed through a gear pump to the "A" and "C" channels of the
three-layer Cloeren feedblock (available from Cloeren Co., Orange,
Tex.) that was set at 216.degree. C. The core layer was made from a
thermoplastic elastomer (available as KRATON D1107 styrene-isoprene
block copolymer, recovering stress (at 300% elongation) of 2.07 MPa
(300 psi), from Shell Chemical Co., Beaupre, Ohio) and conveyed
through an extruder having multiple zones with a single screw
extruder (diameter of 32 mm, L/D of 24/1, available from Killion,
Inc.). The core layer material extruder operated with zone
temperatures increasing from 188.degree. C. to 216.degree. C. The
core layer material was passed to the "B" channel of the Cloeren
feedblock. The resulting multilayered flow stream was passed
through a single orifice film die (having a width of 254 mm (10
inch) and available from EDI, Chippewa Falls, Wis.) that was set at
a temperature of 216.degree. C. The resulting molten film was drop
cast onto a chill roll, which was set at a temperature of
11.degree. C., and collected. The line speed was 12.2 m/min., the
individual flow rates of the outer layer and core layer were such
that each outer layer had a thickness of about 3.1 micrometer
(.mu.m) and the overall film thickness was measured at about 72
.mu.m.
[0103] Sample B was made as Sample A except a layer of Silicone Oil
A (available as DC-200 PDMS oil from Dow Corning, Midland Mich.)
was applied on one side of the three layer film.
[0104] Sample C was made as Sample A except a layer of Silicone Oil
B (available as Part No. 700-01015 PDMS oil from Rheometrics
Scientific, Piscataway, N.J.) was applied on one side of the three
layer film.
[0105] Sample D was made as Sample A except a layer of
pressure-sensitive adhesive (an acrylate-based pressure-sensitive
adhesive (98/2 isooctyl acrylate/acrylic acid) made according to
U.S. Pat. No. 5,804,610, Example 11 (except the ratio of IOA to AA
was 98:2 instead of 97:3) having a thickness of approximately 125
.mu.m was applied on one side of the three layer film by
lamination.
[0106] Each sample was measured for puncture resistance with
Variation A, dynamic coefficient of friction on the surface that
first contacted the puncturing object, and resulting opening area.
Results are reported in Table 1 or in the discussion following the
table.
1TABLE 1 Dynamic Displacement Sample Surface modifier friction
coeff. to break mm (in) A None 0.183 106 (4.167) B Silicone Oil A
0.028 18 (0.712) C Silicone Oil B 0.051 29 (1.153) D Adhesive (a)
304 (11.958) a: The coefficient of friction could not be measured
because the sled did not move before the film broke.
[0107] The data in Table 1 indicate that puncture resistance as
measured by displacement at break decreased when the frictional
properties of the film surface first contacting the puncturing
object decreased. Likewise, the puncture resistance increased when
the surface friction increased.
[0108] For samples A and B, the effective diameters of the opening
and the shaft of the puncturing object were also measured and a
ratio of areas was calculated. The effective area of the puncturing
object, calculated based on the largest diameter of the plastic
pipette that entered the opening, was 2.00 mm. The effective
diameter of the opening for Sample A and B, converting the area of
the often jagged tear in the film into a circle having an
equivalent area, was approximately 1.80 mm and 0.25 mm,
respectively. The ratio of the effective area of the puncturing
object to the effective area of the resulting opening for Samples A
and B were calculated to be 0.81 and 0.016, respectively.
Example 2
[0109] Example 2 illustrates the effect of the dynamic coefficient
of friction of a film on the puncture resistance of a single layer
film.
[0110] Sample A was made by extruding very low density polyethylene
(available as ENGAGE 8200 from Dow Chemical Company, Midland,
Mich.) into a film having a thickness of about 75 .mu.m. The
polymer was conveyed with a single screw extruder through the core
layer slot of the feedblock and single orifice film die used for
Example 1.
[0111] Sample B was made as sample A except a layer of Silicone Oil
A was applied one side of the single layer film.
[0112] Each sample was measured for puncture resistance with
Variation A and dynamic coefficient of friction on the surface that
first contacted the puncturing object. Results are reported in
Table 2.
2TABLE 2 Dynamic Displacement Sample Surface modifier friction
coeff. to break mm (in) A None 3.38 142 (5.594) B Silicone Oil A
0.019 10 (0.402)
[0113] The data in Table 2 indicate that puncture resistance
decreased when the frictional properties of the film surface first
contacting the puncturing object decreased.
Example 3
[0114] Example 3 illustrates the effect of stretching and relaxing
a film on the puncture resistance of the film.
[0115] Sample A was made in a manner similar to Sample A of Example
1 except the three layer film was further consecutively stretched
in one direction to 500% of its original length in both the machine
and transverse directions. Then the film was allowed to recover
until it reached a steady state in approximately 10 minutes.
[0116] Sample A and Sample A of Example 1 were measured for
puncture resistance with Variation B. Results are reported in Table
3.
3 TABLE 3 Displacement Sample Modification to break mm (in) A
Stretched to 500% & relaxed 202 (7.943) 1-A none 139
(5.453)
[0117] The data in Table 3 indicate that puncture resistance
increased when the film was stretched and relaxed before being
punctured.
Example 4
[0118] Example 4 illustrates the effect of stretching a film on the
puncture resistance of the film.
[0119] Sample A was made by further stretching Sample A of Example
1 in one direction to 300% of its original length while held in the
testing sample holder (and was punctured while it was
stretched).
[0120] The sample was measured for puncture resistance with
Variation A. Results are reported in Table 4 together with that of
Sample A of Example 1.
4 TABLE 4 Displacement Sample State to break mm (in) A Stretched to
300% 66 (2.579) 1-A original 106 (4.167)
[0121] The data in Table 4 indicate that puncture resistance
decreased when the film was punctured while it was stretched.
Example 5
[0122] Example 5 illustrates how a film can be made less or more
puncture resistance depending on which side of a film consisting of
two layers of different materials first contacts the puncturing
object.
[0123] Sample A was made by further applying different materials to
each side of Sample A of Example 1. Silicone Oil A was applied to
side one of the film in a manner similar to Sample B of Example 1
and adhesive was applied to side two in a manner similar to Sample
D of Example 1.
[0124] The sample was measured for puncture resistance with
Variation A. Results are reported in Table 5 together with that of
Sample A of Example 1.
5 TABLE 5 Displacement Sample Surface to break mm (in) A--side 1
Silicone Oil A 29 (1.136) 1-A original 106 (4.167) A--side 2
Adhesive 284 (11.182)
[0125] The data in Table 5 indicate that the film was significantly
less puncture resistant when the penetrating means first contacted
the side with the silicone oil rather than the side with the
adhesive.
Example 6
[0126] Example 6 illustrates another way a film can be made less or
more puncture resistant depending on which side of a film
consisting of two layers of different materials first contacts the
puncturing object.
[0127] Sample A was made in a manner similar to that of Sample A of
Example 1 except the side-2 outer layer material was a metallocene
catalyzed very low density polyethylene (VLDPE) available as ENGAGE
8200 from Dow Chemical). The VLDPE was conveyed with a single screw
extruder having multiple zones (Killion Model KLB075) that was
operating with zone temperatures increasing from 160.degree. C. to
216.degree. C. The material was passed to the C channel of the
three-layer feedblock. The line speed was 7.77 n/min. and the
overall thickness was measured at 91 .mu.m.
[0128] Each side of the sample was measured for puncture resistance
with Variation B. Results are reported in Table 6.
6 TABLE 6 Displacement Sample Surface to break mm (in) A--side 1
HDPE 203 (7.984) A--side 2 VLDPE 327 (12.871)
[0129] The data in Table 6 indicate that this film also had
different puncture resistance depending on which outer layer
material was first contacted with the penetrating means.
Example 7
[0130] Example 7 illustrates the effect of outer layer thickness on
puncture resistance.
[0131] Sample A-D were made as Sample A of Example 1 except gear
pump settings on the outer layer extruder were adjusted to obtain a
different outer layer thickness for each sample, as reported in
Table 7, while the core layer extruder settings and line speed were
unchanged.
[0132] The samples as well as Sample A of Example 1 were measured
for puncture resistance with Variation B. Results are reported in
Table 7.
7 TABLE 7 Gear pump Outer layer Displacement Sample setting rpm
thickness .mu.m to break mm (in) 1-A 7 3.1 139 (5.453) A 10 3.5 122
(4.785) B 13 4.6 90 (3.552) C 18 6 76 (3.008) D 23 6.4 64
(2.510)
[0133] The data in the above table indicate that puncture
resistance decreases as outer layer thickness increases for the
construction tested.
Example 8
[0134] Example 8 illustrates the effect of total film thickness on
puncture resistance.
[0135] Sample A-C were made as Sample C of Example 7 except line
speed settings were adjusted to obtain a different total film
thickness for each sample, as reported in Table 8 (both extruder
settings were unchanged).
[0136] The samples were measured for puncture resistance with
Variation B. Results are reported in Table 8 together with that of
Sample C of Example 7.
8 TABLE 8 Line speed Total Displacement Sample meters/minute
thickness .mu.m to break mm (in) A 7.6 122 55 (2.184) B 9.14 94 69
(2.730) 7-C 12.2 76 76 (3.008) C 15.2 60 82 (3.242)
[0137] The data in the above table indicate that puncture
resistance decreases as total film thickness increases for the
construction tested.
Example 9
[0138] Example 9 illustrates the effect of different outer layer
materials, each having a different elongation at break, on puncture
resistance of a three layer construction.
[0139] Sample A was made as Sample A of Example 1 except the outer
layer material was HDPE B (available as DOWLEX IP60 HDPE,
elongation percent at break of 225, from Dow Chemical); the
extruders reached upper temperatures of 232.degree. C., and the die
was set at a temperature of 232.degree. C. Also, the line speed and
extruder flow rates were changed to result in a total film
thickness of 140 .mu.m with outer layer thicknesses of about 10
.mu.m each.
[0140] Sample B and Sample C were made as Sample A except the outer
layer material was HDPE A (described in Example 1) and HDPE C
(ALATHON M5865 HDPE from Equistar, elongation percent at break of
800), respectively.
[0141] The samples were measured for puncture resistance with
Variation B. Results are reported in Table 9.
9 TABLE 9 Outer layer Elongation Displacement Sample Material
Percent to break mm (in) A HDPE B 225 62 (2.422) B HDPE A 300 72
(2.828) C HDPE C 800 136 (5.374)
[0142] The data in the above table indicate that as the elongation
at break of the outer layer increased, the puncture resistance of
the outer layer increased.
Example 10
[0143] Example 10 illustrates the effect of outer layer thickness
on the puncture resistance and resealability of a multilayer
film.
[0144] Sample A, B and C were the same as Sample A, B and C of
Example 7 except the films were punctured with a plastic pipette
having a shaft diameter of 2.0 mm instead of a metal rod having a
shaft diameter of 13.7 mm.
[0145] The samples were measured for puncture resistance with
Variation A and the resulting area of the opening. Results are
reported in Table 10.
10TABLE 10 Outer layer Displacement Ratio of opening Sample
thickness .mu.m to break mm (in) area to pipette area A 3.5 44
(1.719) 0.0070 B 4.6 38 (1.482) 0.0041 C 6 22 (0.852) 0.0009
[0146] As seen in Table 10, the ratio of the opening area to
puncturing object area decreased as the film was less puncture
resistant.
Example 11
[0147] Example 11 illustrates the effect of a different core
material with different recovering stress on puncture resistance of
an outer layer/core layer/outer layer construction.
[0148] Sample A was made as Sample B of Example 9 except the core
material was KRATON D1112P, having a recovering stress of 1.45 MPa
(210 psi), available from Shell Chemical Company.
[0149] The sample was measured for puncture resistance. Results are
reported in Table 11 with those of Sample B of Example 9.
11TABLE 11 Recovering Displacement to Sample Core Material stress
MPa break mm (in) 9-B KRATON D1107 2.07 72 (2.828) A KRATON D1112P
1.45 51 (1.999)
[0150] The data in the above table indicate that as the recovering
stress of the core material decreases, the puncture resistance of
the film decreases. The elongations at break of the core layer
materials of Examples 9-B and 11A were substantially the same at
1300% and 1400%, respectively.
[0151] Patents, patent applications, and publications disclosed
herein are hereby incorporated by reference (in their entirety) as
if individually incorporated. It is to be understood that the above
description is intended to be illustrative, and not restrictive.
Various modifications and alterations of this invention will become
apparent to those skilled in the art from the foregoing description
without departing from the scope of this invention, and it should
be understood that this invention is not to be unduly limited to
the illustrative embodiments set forth herein.
* * * * *