U.S. patent application number 10/518478 was filed with the patent office on 2005-12-08 for microscope slide cover with integrated reservoir.
Invention is credited to Goris, George, Henderson, Chester, Mckinlay, Jonathan, McLellan, Andrew.
Application Number | 20050270642 10/518478 |
Document ID | / |
Family ID | 3836651 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050270642 |
Kind Code |
A1 |
McLellan, Andrew ; et
al. |
December 8, 2005 |
Microscope slide cover with integrated reservoir
Abstract
A cover (10) for substrate (not shown) including: a body (12)
defining a cavity (18), for positioning over the substrate (not
shown) to form a reaction chamber (18); and a projection (13)
extending from the body (12) to define a fluid reservoir (14), when
the cover (10) is fitted to the substrate (not shown), the fluid
reservoir (14) being in fluid communication with the cavity
(18).
Inventors: |
McLellan, Andrew; (Surrey
Hills, AU) ; Goris, George; (Beaconsfield, AU)
; Henderson, Chester; (Mount Waverley, AU) ;
Mckinlay, Jonathan; (Hawthorn East, AU) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
3836651 |
Appl. No.: |
10/518478 |
Filed: |
July 26, 2005 |
PCT Filed: |
June 20, 2003 |
PCT NO: |
PCT/AU03/00778 |
Current U.S.
Class: |
359/391 |
Current CPC
Class: |
G02B 21/34 20130101;
B01L 9/52 20130101; Y10T 436/25 20150115; B01L 2300/0822 20130101;
Y10T 436/2575 20150115; G01N 2035/00138 20130101; B01L 2400/0406
20130101; B01L 3/508 20130101; B01L 2300/021 20130101; B01L
2300/045 20130101 |
Class at
Publication: |
359/391 |
International
Class: |
G02B 021/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2002 |
AU |
PS 3090 |
Claims
1. A cover for a substrate including: a body defining a cavity, for
positioning over the substrate to form a reaction chamber; and a
projection extending from the body to define a fluid reservoir,
when the cover is fitted to the substrate, the fluid reservoir
being in fluid communication with the cavity.
2. A cover, as claimed in claim 1, wherein the cavity extends the
full width of a sample holding region of the substrate.
3. The cover as claimed in one of claim 1 wherein a protrusion
extends from the projection, to assist in wicking fluid into the
reservoir.
4. A cover as claimed in claim 3, wherein the reservoir is defined
by a first section, angled at least at substantially 60.degree.
relative to the cavity, and a second section, positioned between
the cavity and the first section, and orientated at a reduced angle
relative to the cavity, as compared to the first section.
5. A cover as claimed in claim 4, wherein the second section is
angled at least at substantially 15.degree..
6. A cover as claimed in any one of claim 1 wherein the cover is
made from a polymer material.
7. A cover as claimed in any one of claim 1 wherein the cavity
includes a coating of reduced surface roughness than the polymer
material.
8. A cover as claimed in claim 7 wherein the cavity includes a
coating with reduced porosity.
9. A cover as claimed in claim 7 wherein the cavity has one or more
coatings.
10. A cover as claimed in claim 9 wherein a first coating is a
material having similar properties to the material of the
slide.
11. A cover as claimed in claim 10 wherein the first coating is
silicon dioxide.
12. A cover as claimed in claim 11 wherein a second coating is
placed intermediate a first coating to provide improved contact
properties between the cover and first coating.
13. A cover as claimed in claim 1 wherein the width of the cavity
of the cover is the no larger than the width of a microscope
slide.
14. A cover as claimed in claim 1, wherein the cavity is
substantially planar.
15. A cover as claimed in claim 1, further including a locator for
controlling and locating the cover, the locator being arranged at
an end of the cover opposite the projection.
16. A cover as claimed in claim 1, further including a second
reservoir, at an opposite end of the cover.
17. A cover as claimed in claim 1, wherein wall portions are
located at the edge of the cover, surrounding the cavity on two or
more sides.
18. A cover as claimed in claim 17, wherein the reservoir is
defined between the projection, and legs located on either side of
the cover.
19. A cover as claimed in claim 18, wherein legs extend along the
sides of the cavity to form the wall portions.
20. A cover according to claim 18 wherein the cover is supported
upon the substrate on the wall portions.
21. A covertile according to claim 15 wherein the cavity extends to
an end edge of the cover adjacent the locator.
22. A cover as claimed in claim 1, wherein the cover has associated
wing structures that allow the cover to be engaged and pivoted
relative to the substrate so as to open the reaction chamber and
allow the slide to be cleared of fluid.
23. A combination of a substrate and a cover, as claimed in claim
1, wherein the cavity of the cover is arranged to face the
substrate so as to form a reaction chamber.
24. A method of treatment of a sample on a sample holding region of
a substrate including locating a cover, as claimed in claim 1, over
the substrate, so that the cavity of the cover faces the substrate
to form a reaction chamber over the sample holding region, and
depositing fluid into the fluid reservoir to allow the fluid to be
drawn into the reaction chamber, as required.
25. A method as claimed in claim 24, further including sliding the
cover relative to the substrate to vary a degree of overlap between
the cover and the sample holding region, which results in a
corresponding variation in the reaction chamber volume.
26. A method as claimed in claim 24, further including sliding the
cover relative to the substrate until wing structures associated
with the cover are engaged and lifted relative to the substrate to
pivot the cover into an open condition, and allow fluid to drain
from the reaction chamber.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a cover for a substrate,
and in one form a cover for use with a microscope slide.
BACKGROUND OF THE INVENTION
[0002] Microscope slides are commonly used to view samples of
material under a microscope. The samples may contain human tissue,
and may require treatment such as staining, so that properties of
the sample can be identified. Other materials such as DNA, RNA, or
proteins may be included on the slide.
[0003] It is common for several reactions to be undertaken on a
sample on a slide. Once the reactions have taken place the slide
may be viewed under a microscope. Performing the reactions on the
slide can be difficult to automate, as the tissue samples require
careful preparation and certain reactions require carefully
controlled environments.
SUMMARY OF THE PRESENT INVENTION
[0004] In accordance with the present invention, there is provided
a cover for a substrate including:
[0005] a body defining a cavity, for positioning over the substrate
to form a reaction chamber; and
[0006] a projection extending from the body to define a fluid
reservoir, when the cover is fitted to the substrate, the fluid
reservoir being in fluid communication with the cavity.
[0007] Preferably the cavity extends the full width of a sample
holding region on the substrate.
[0008] Preferably, a protrusion extends from the projection, to
assist in wicking fluid into the reservoir.
[0009] Preferably, the reservoir is defined between the projection,
which is spaced from the substrate, and legs located at sides edge
of the cover.
[0010] In one form the projection is formed front two sections, the
first section is angled at least at substantially 60.degree.
relative to the cavity and the second section is angled at least at
substantially 15.degree..
[0011] In one form, the cover further includes a second reservoir,
at an opposite end of the cover.
[0012] Preferably wall portions are located at the edge of the
cover, surrounding the cavity on two or more sides.
[0013] In one form the legs extend along the sides of the cover to
form the wall portions.
[0014] In a preferred form, the cover includes a locator for
controlling and locating the cover, the locator being arranged at
an end of the cover opposite the projection.
[0015] In one form the cavity extends to an end edge of the cover
adjacent the locator.
[0016] In one form the cover is supported on the substrate by the
wall portions.
[0017] Preferably, the cover is made from a polymer material.
[0018] In one form the cavity includes a coating of reduced surface
roughness than the polymer material.
[0019] In another form the cavity includes a coating with reduced
porosity.
[0020] In another form the cavity has one or more coatings.
[0021] Preferably a first coating is a material having similar
properties to the material of the slide.
[0022] Preferably the first coating is silicon dioxide.
[0023] Preferably a second coating is placed intermediate a first
coating to provide improved contact properties between the cover
and first coating.
[0024] Preferably, the cover has associated wing structures that
allow the cover to be engaged and pivoted relative to the substrate
so as to open the reaction chamber and allow the slide to be
cleared of fluid.
[0025] In another aspect, there is provided a combination of a
substrate and a cover, as described above, wherein the cavity of
the cover is arranged to face the substrate so as to form a
reaction chamber.
[0026] In yet another aspect, there is provided a method of
treatment of a sample on a sample holding region of a substrate,
including locating a cover, as described above, over the substrate,
so that the cavity of the cover faces the substrate to form a
reaction chamber over the sample holding region, and depositing
fluid into the fluid reservoir to allow the fluid to be drawn into
the reaction chamber, as required.
[0027] Preferably, the method further includes sliding the cover
relative to the substrate to vary a degree of overlap between the
cover and the sample holding region, which results in a
corresponding variation in the reaction chamber volume.
[0028] Preferably, the method further includes sliding the cover
relative to the substrate until wing structures associated with the
cover are engaged and lifted relative to the substrate to pivot the
cover into an open condition, and allow fluid to drain from the
reaction chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The invention is described, by way of non-limiting example
only, with reference to the accompanying drawings, in which:
[0030] FIG. 1 shows an example of a microscope slide;
[0031] FIGS. 2 (a)-(c) show top, side and bottom views of a first
example of a cover for a slide;
[0032] FIG. 3 shows a perspective view of the cover of FIG. 2;
[0033] FIGS. 4 (a)-(c) show farther views of the cover of FIG. 2
located on the slide of FIG. 1;
[0034] FIG. 5 is a perspective view of the cover and slide
arrangement of FIG. 4, showing a cutaway section of the cover;
[0035] FIG. 6 shows a schematic cross section of the cover and
slide of FIG. 5;
[0036] FIG. 7 shows a perspective view of a tray adapted to locate
covers and slides;
[0037] FIGS. 8 (a) and (b) show schematic top and sectional side
views, respectively, of a further example of a cover;
[0038] FIGS. 9 (a) and (b) show schematic top and sectional side
views, respectively, of a further example of a cover;
[0039] FIGS. 10 (a) and (b) show schematic top and sectional side
views, respectively, of a further example of a cover;
[0040] FIGS. 11 (a) and (b) show schematic top and sectional side
views, respectively, of a further example of a cover,
[0041] FIGS. 12 (a) and (b) show schematic top and sectional side
views, respectively, of a further example of a cover;
[0042] FIGS. 13 (a) and (b) shows schematic top and sectional side
views, respectively, of a further example of a cover;
[0043] FIGS. 14 (a) and (b) show top and bottom perspective views,
respectively, of a further example of a cover;
[0044] FIG. 15 shows a schematic side view of a nose portion of a
cover;
[0045] FIG. 16 (a) and (b) show schematic top and sectional side
views, respectively, of a further example of a cover;
[0046] FIG. 17 shows a schematic side view of a further example of
a nose portion of a cover;
[0047] FIG. 18 shows the cover of FIG. 2 mounted to the tray of
FIG. 7;
[0048] FIGS. 19 (a)-(c) shows the cover of FIG. 2 in various
positions over the slide of FIG. 1; and
[0049] FIGS. 20 (a) and (b) show a bottom perspective view and
enlarged partial perspective view, respectively of a modified
cover.
DETAILED DESCRIPTION
[0050] A microscope slide 1 is shown in FIG. 1 as including an
upper surface 2 containing a sample 3. The slide 1 is identified by
a unique bar code 4. The sample 3, such as a thinly sliced tissue
section, is located on the slide 1 in a sample holding region 5,
which needs to be covered by a cover, such as shown in FIG. 2, for
subsequent application of test fluids and the like.
[0051] FIGS. 2 (a)-(c) and FIG. 3 show a cover 10 as having a body
12, a fluid receiving zone 14, a locating means 16 and a cavity 18
on an underside face 19. Surrounding the cavity 18 on two sides is
a wall portion 20. At one end of the cover 10, the wall portion 20
joins with legs 21 which extend upwardly and away from the face 19.
The legs 21 are spanned by a projection 13 which defines a fluid
reservoir 17, between an underside of the projection and the legs
21.
[0052] The cover 10 is shown fitted to a slide 1 in FIGS. 4 and 5.
The fluid reservoir 17 is shown roost clearly in FIG. 4 (c) where a
detailed view of part of a section A-A taken across the cover 10
and slide 1 is illustrated. The projection 13, with leg 21 at
either end, is raised relative to the slide 1, to form a volume
capable of holding fluid dispensed onto the slide 1. In this way
fluid reservoir 17 enables fluid dispensed onto slide 1 to be held
until required, without spilling off an edge of the slide. The
projection 13 further assists in spreading the fluid across the
full width of the cavity
[0053] The overlap of the cavity 18 with the slide 1 forms what may
be described as a reaction chamber, as illustrated in FIG. 6. The
cavity may vary according to application, typically from 20-200
microns. The wall portion 20 is adapted to support the cover on the
slide 1. The cavityed face 22, wall portion 20 and sample holding
region 5 of a slide 1 form a reaction chamber 24 when the cover 10
is placed at least partially over the sample holding region 5.
[0054] The fluid reservoir 17 is typically sized to be larger than
the volume of the reaction chamber 24, for example 150% of the
volume of the reaction chamber. This provides sufficient volume of
fluid to fill the reaction chamber completely, while allowing some
excess to flush the chamber, and an amount to be retained in the
fluid reservoir to provide a reservoir for evaporation.
[0055] Clamping forces may also be applied to the cover once loaded
onto the slide, and these forces are designed to provide a seal
between the wall portions 20 and the upper surface of the slide 1.
This is to restrict fluid leakage from the side of the cover. In
one example (not shown) the wall portions may have an additional
member to assist sealing of the wall portions with the upper
surface 2 of the slide 1. This additional member may be a softer
polymer or rubber material.
[0056] The cover 10 also includes engaging surfaces in the form of
wings 26. The wings 26 are adapted to engage ramps 28 of a tray 21
shown in FIG. 7, to thereby lift the cover clear of the surface of
the slide 1. An example of the wings lifting the cover free is
shown more clearly in FIG. 18. The cover 10 may be controlled by an
arm (not shown) moving the locating means 16. The cover 10 may be
placed in a number of positions over the slide, exemplified by the
positions of the cover relative to the slide shown in FIG. 19. In
FIG. 19 (a), the cover 10 is in an open position relative to the
slide 1, as the sample is exposed and open. FIG. 19 (b) shows the
cover in a partially closed position, and FIG. 19 (c) shows the
cover in a fully closed position, where the sample is completely
covered by the cover and is therefore wholly contained within the
reaction chamber 24. The reaction chamber formed by the cover and
cavity 18, as shown in FIG. 5, extends over most of the slide 1.
However it is possible that the sample may be placed more towards
the end of the slide distal from the bar code 4, and therefore a
smaller reaction chamber 24 is required. Reducing the size of the
reaction chamber 24 reduces the amount of fluid required to fill
the chamber, which can be important where expensive or scarce
fluids are used. It is possible to form a smaller reaction chamber
with the cover 10, by only covering a porion of the slide 1 with
the cover 10. This position is shown in FIG. 18 (b).
[0057] Variations in cover constructions are schematically shown in
FIGS. 8-17. In FIGS. 8-17, only the front segments of the covers
are shown, and the locating means 16 have been omitted from view
for clarity and like parts are denoted by like reference
numerals.
[0058] In FIG. 8 (a) a cover 10 is shown having a body 12,
projecting legs 21, a protruding section 13 and an indent 30. The
projecting legs 21 either side of the body 12 form a fluid
receiving zone 14. When placed onto a slide, fluid may be dispensed
into the fluid receiving zone, where it spreads in a circular
fashion to contact the protruding section 13. The indent 30 allows
the fluid to contact a wider portion of the protruding section 13
than if the front edge of the protruding section was straight (as
shown in FIG. 9). Once the fluid is in contact with the protruding
section 13, it wicks across the width of the cavity 18. If suction
is applied at the rear of the cavity, or the cover is moved along
the slide from an open position to a more closed position, then the
fluid begins to fill the cavity 18. When the cavity 18 has moved
across the sample 3, it forms the reaction chamber 24 as the fluid
may react with the sample 3.
[0059] FIGS. 9 (a) and (b) show a more simple construction of a
cover 10 that may be used in some circumstances. The operation of
the cover 10 is the same as the operation of the cover 10 in FIGS.
8 (a) and (b).
[0060] FIG. 10s (a) and (b) show a cover 10 having a body 12 with
projecting legs 21. A protruding section 13 and a bar 31 surround a
fluid receiving zone 14 for receiving fluid. The fluid may be
dispensed onto the protruding section 13, where it flows down and
onto the slide surface 2. The protrusion 13 and bar 31 cause the
fluid to spread across the width of the cavity 18, enabling the
cavity to be filled with fluid.
[0061] The covers 10 of FIGS. 11, 12 and 16 operate in similar ways
to those described above.
[0062] In relation to all of the above-described coves, it should
be appreciated that the covers are generally 25 mm across, and the
cavity 18 is typically only 20-200 micrometres high. As such,
overall fluid dispense volumes may be in the order of 20-300
microlitres.
[0063] FIG. 13 (a) shows another cover 10 having a body 12, legs 21
and a fluid dispenser 100 dispensing fluid 102 onto the slide 1. In
FIG. 13 (a), the fluid 102 has already been dispensed, and has
formed a fluid reservoir in the fluid reservoir 17. The schematic
Figure shows a typical wicking pattern formed by the fluid as it
contacts the cover 1. In FIG. 13 (b), the fluid is just being
dispensed onto the projection 13. In the volumes dispensed, the
fluid forms a pool of comparable size to some of the cover
features. Not only does the fluid flow forward of the cover as
shown in FIG. 13 (a), but it also flows under the cover to at least
partially fill cavity 18. As mentioned above the fluid may be drawn
into the cavity further by movement of the cover over the slide or
suction applied to the rear of the cavity 18.
[0064] FIG. 14 (a) and (b) shows a further embodiment of a cover 10
where like reference numerals are again used to denote like ports.
The cover has a fluid reservoir 17, a projection 13, and a
protrusion in the form of nib 15. Fluid may be deposited directly
On the nib 15 so that the fluid rolls over the projection 13 into
reservoir 14, and to the cavity 18, as required. If fluid is placed
too far ahead of the cover, there are circumstances that may cause
the fluid to reach the edge of the slide before wicking across the
width of the cavity 18. It has been found that using the projection
13 causes the dispensed fluid to contact the covertile and spread
along the full width of the cavity 13, due to the positive
attraction of the covertile and the fluid. The capillary forces in
the cavity cause the fluid to spread out, and the reservoir holds
sufficient fluid to ensure that fluid dispensed onto the slide at
least fills the cavity 18. The nib 15 is useful in that if the
pipette is not placed to dispense the fluid accurately onto the
slide, and for example misses a few millimetres in front of the
projection, the nib 15 will be likely to contact the fluid, which
will be drawn to the protrusion and into the reservoir. This
assists in reducing bubble or void formation within the cavity. The
nib 15 may extend approximately 1-5 mm from the projection 13.
[0065] FIG. 17 shows an example of how fluid spreads across a slide
when deposited in front of a cover 50. A variety of profiles for
the underside of a projection 15 may be employed.
[0066] In use, a cover 10 is placed on a slide 1, as shown in FIGS.
4, 5 and 6 to cover the sample 3. The slide 1 will typically be in
a tray 21 as shown in FIG. 7, said tray 21 able to hold, for
example, 10 slides and covers of the examples shown. The tray 21
may then be placed into a biological reaction apparatus, such as
that disclosed in Australian Provisional Patent Application No.
PS3114/02 by the same applicant, titled "Method and Apparatus for
Providing a Reaction Chamber", filed 20 Jun. 2002, and its
associated international patent application, filed 20 Jun. 2003,
the contents of which are hereby incorporated by reference.
[0067] Once the tray 21 is loaded into the apparatus (not shown)
the slides 1 are held in position, typically at an angle of 5
degrees to the horizontal as shown schematically in FIG. 13 (b), 15
or 17. The cover 10 is then moved by an arm (not shown) engaging
the locating means 16. Typically, during a sequence referred to as
an "open fill", the cover 10 is moved longitudinally along the
surface of the slide 1 until the sample 3 is exposed. A fluid is
then dispensed by a dispensing means 100 such as a probe attached
to a pump, onto the fluid receiving zone 13 (as shown in FIG. 13
(b)). The amount of fluid dispensed is typically sufficient to fill
the reaction chamber 24. The use of the cover 10 with this fill
mechanism or methodology allows a small volume of fluid to be
uniformly distributed across the reaction chamber 24. Distributing
the fluid across the reaction chamber 24 evenly and without bubbles
or air spaces allows reactions to take place on the sample 3 with
greater consistency. Also, dispensing fluid into an empty receiving
zone where the reaction chamber already contains fluid causes the
fluid within the chamber to be replaced by the fluid in the
receiving zone minimising mixing of the fluid in the reaction
chamber and newly dispensed fluid. The dimensions of the reaction
provide a smooth flow of fluid from the reaction chamber such that
there is little mixing of the fluids. This is advantageous as it
allows a previous fluid to be replaced accurately, with minimal
original fluid remaining to contaminate later fluids or reactions.
This reduces the number of washes required to clear the reaction
chamber 24
[0068] The volume of fluid in a reaction chamber 24 may be, for
example 150 microlitres or less, although volumes may vary
depending on the application and the reaction chamber
dimensions.
[0069] The reaction chamber 24 is able to retain fluid due to the
surface tension of the fluid, unless additional fluid is added to
the fluid receiving zone, or suction is applied (typically through
reduced air pressure) at the end of the slide opposite the fluid
receiving zone. The reaction chamber may be filled as it is formed
by the cover 10 being moved along the surface of the slide 1 to
cover the sample holding region 52. Alternatively, the reaction
chamber may be filled without the cover being moved relative to the
slide, due to the process of capillary wicking of dispensed fluid
into the reaction chamber.
[0070] In the present examples the cover may be clamped to the
slide when not in motion or retracted for an initial fill. The
clamping mechanism (not shown) places force around the edge of, for
example, cover 10 adjacent the wall portions 20 to locate the cover
10 with respect to the slide 1 during a reaction.
[0071] During the withdrawal of the cover 10 from the slide 1 it is
sometimes desirable to remove the cover from contact with the
slide. In order to accomplish this, wings 26 engage the ramps 28 to
lift the cover clear of the slide. This causes the cover 10 to lift
off the slide 1 to prevent fluid contact between the slide 1 and
cover 10. In this way the slide can be cleared of virtually all
fluid.
[0072] Parts of the cover may have different material properties
compared to the properties of the material of the cover body 12,
which is typically plastic. In one example (not shown) the cavity
may have different material properties, in order to provide a
reaction chamber 24 with certain material properties. A clear
plastic material has been found to be suitable for the body 12 of
the cover 10, to provide suitable mechanical properties such as
reasonable strength and rigidity. The cover needs to be
sufficiently strong to be moved while clamping forces are applied
to the cover, as the clamping forces assist in providing a sealing
surface between the walls 20 of the cover 10 and the upper surface
of the slide 1. The cover may be moved to empty or fill the
chamber, or also, to promote fluid movement within the reaction
chamber to assist a reaction.
[0073] The cover should ideally have some flexibility, as it is
desirable that upon application of the clamp, the cavityed face
should deflect somewhat. This has been found to assist in moving
the fluid within the reaction chamber and therefore increases the
exposure of the sample to the fluid.
[0074] Other properties of the cover 10 include the ability to
restrict the heat loss from the surface of the slide 1. Typically
the slide will be mounted on a heated block, and the cover will be
placed over the sample on the slide. Heating the slide heats the
sample and the fluid in the reaction chamber. If there is excessive
heat loss from the cover 10 it is difficult to regulate the
temperature of the fluid by beating the slide 1. Further, there may
be an excessive temperature gradient across the reaction chamber
24, which is undesirable.
[0075] The cavityed face 19, as shown in FIG. 2, may have different
surface properties to the rest of the cover. It has been found to
be desirable to have similar material properties for the upper
surface of the slide 2 and the cavity 18. In one example, it is
possible to coat the surface of the cavity with a material, such as
silicon dioxide. This coating may be approximately 110 nm thick.
The coating provides a surface with material properties similar to
that of a glass slide. It has also been found that there are
benefits in applying a thin layer (for example 0.5-6 nm) of
Chromium Oxide (Cr2O3) to the cavity before applying the silicon
dioxide layer. This application of an intermediate layer between
the silicon dioxide and plastic provides better adhesion and better
thermal expansion properties for the cavity. Further, coatings in
general may be used to improve the flatness of the cavity (which
reduce nucleation sites and therefore bubble formation at high
temperatures). The coatings may be used to modify the capillary
flow characteristics of the fluid within the reaction chamber,
create an impermeable barrier for gas or liquid between the cover
and fluid in the reaction chamber, or provide a chemically inert
surface.
[0076] In another example, it is possible to replace the cavityed
face 19 with a glass insert supported by the plastic body 12 of the
cover 10. It may also be possible to change the surface properties
of the plastic by plasma discharge.
[0077] The covers shown in the examples may be used at temperatures
approaching 100 degrees Celsius, especially when used for in-situ
hybridisation reactions. At higher temperatures, the fluid
evaporates and bubbles are produced. The heating may also cause the
cover to bow--the cavity surface is hotter than the top of the
cover and expands more, causing the cavity surface to `sag` towards
the slide. This helps to remove the bubbles, as the fluid wants to
occupy the smaller spaces more than the bubbles do. The bubbles
congregate at the ends of the cavity, and must be allowed to
escape.
[0078] Experiments have demonstrated that a chamfer at the end of
the cavity reliably allows the bubbles to escape to atmosphere. The
existing reservoir 17 can be redesigned as illustrated in FIG. 20,
where a modified cover 60, similar to that shown in FIG. 14, is
shown with a chamfer 61 to assist in releasing bubbles, without
affecting the even fluid flow through the cavity 18. The chamfer
forms a first angled section 62 at about 60.degree. relative to the
cavity and slide surface.
[0079] Fluid evaporation rate is, however, directly linked to the
surface area of the fluid exposed to atmosphere--a larger surface
area will evaporate faster, and require more frequent
replenishment. If the bubble escape angle is steep, the evaporation
rate will increase.
[0080] This problem can be overcome by using two angles--a shallow
angled section at, say, 15.degree. between the cavity and the
chamfer, to minimise evaporation, leading into the steeper angle
for bubble release, which also serves to increase the volume of the
reservoir.
[0081] The cover 60 is also provided with a second, identically
shaped reservoir 63 at an opposite end thereof. The second
reservoir 63 can also be used to replenish fluid within the cavity
during heating and to allow bubbles to escape. The second reservoir
63 thereby allows for increased control of fluid conditions within
the reaction chamber.
[0082] The embodiments of FIGS. 14 and 20 are considered to
represent what is currently believed to be the best known method of
performing the cover aspect of the invention.
* * * * *