U.S. patent application number 11/159856 was filed with the patent office on 2005-11-17 for method of setting and actuating a multi-stable micro valve and adjustable micro valve.
Invention is credited to Ginggen, Alec.
Application Number | 20050252553 11/159856 |
Document ID | / |
Family ID | 8178870 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050252553 |
Kind Code |
A1 |
Ginggen, Alec |
November 17, 2005 |
Method of setting and actuating a multi-stable micro valve and
adjustable micro valve
Abstract
A micro valve and a method for setting or actuating a micro
valve for use in fluidic applications includes cooling an array of
actuating members made of Shape Memory Alloy (SMA) material. The
SMA material is cooled to a temperature equal to or below the
temperature at which a transformation from austenitic to
martensitic state occurs so that the entire array of SMA actuating
members is either fully or partially in the martensitic state. At
least one of the actuating member is selected to correspond to a
pre-determined opening pressure or flow resistance. Each of the
actuating members are heated individually, except the previously
selected one, to a temperature equal to or above the temperature at
which a transformation from the martensitic state to the
austensitic state occurs.
Inventors: |
Ginggen, Alec; (Neuchatel,
CH) |
Correspondence
Address: |
PHILIP S. JOHNSON
JOHNSON & JOHNSON
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
08933-7003
US
|
Family ID: |
8178870 |
Appl. No.: |
11/159856 |
Filed: |
June 23, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11159856 |
Jun 23, 2005 |
|
|
|
10263504 |
Oct 3, 2002 |
|
|
|
6926246 |
|
|
|
|
Current U.S.
Class: |
137/334 |
Current CPC
Class: |
F16K 99/0001 20130101;
Y10T 137/6416 20150401; F16K 2099/0094 20130101; F15C 5/00
20130101; A61M 2205/3523 20130101; F16K 2099/0088 20130101; F16K
2099/0069 20130101; F16K 99/0011 20130101; A61M 27/006 20130101;
F16K 99/0036 20130101 |
Class at
Publication: |
137/334 |
International
Class: |
F16K 031/66 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2001 |
EP |
01123923.3 |
Claims
What is claimed is:
1. A method of setting and actuating an adjustable micro valve that
comprises the steps of: cooling an array of actuating members made
of SMA material, to a temperature equal or below the temperature at
which a transformation from austenitic to martensitic state occurs
so that the entire array of SMA actuating members is either fully
or partially in the martensitic state; selecting at least one of
the actuating members corresponding to a pre-determined opening
pressure or resistance to flow; and heating individually each of
the actuating members except the previously selected member to a
temperature equal to or above the temperature at which a
transformation from the martensitic state to the austensitic state
occurs.
2. A method according to claim 1 wherein the actuating members are
made of a SMA material having two stable states at body temperature
and an hysteresis comprised between 10 and 40 degrees
centigrade.
3. A method of setting and actuating an adjustable micro valve
comprising the steps of: heating an array of actuating members made
of SMA material, to a temperature equal or above the temperature at
which a transformation from martensitic to austenitic state occurs
so that the entire array of SMA actuating members is either fully
or partially in the austenitic state; selecting at least one of the
actuating members corresponding to a pre-determined opening
pressure or resistance to flow; and cooling individually the
selected actuating members to a temperature equal or below to the
temperature at which a transformation from the austenitic state to
the martensitic state occurs.
4. A method according to claim 3 wherein the actuating members are
made of a SMA material having two stable states at body temperature
and an hysteresis comprised between 10 and 40 degrees
centigrade.
5. An adjustable micro valve comprising: a base element having a
base plate face and at least one passage for the flow of fluid; at
least one array of actuating members made of a SMA material
arranged on the base plate face; means for cooling at least one of
the actuating members; and means for heating at least one of the
actuating members.
6. An adjustable micro valve according to claim 5, further
comprising an elastic element securing a ball in the seat of an
opening and in that the actuating members are conformed so that one
of their free ends interacts with a portion of the elastic element
allowing alteration of its elasticity.
7. An adjustable micro valve according to claim 5, wherein the
actuating members are conformed so that one of their free ends
closes a corresponding orifice in the base element.
8. An adjustable micro valve according to claim 5, wherein the
cooling means include at least one Peltier cell integrated in the
base element in the vicinity of the at least one array of SMA
actuating members.
9. An adjustable micro valve according to claim 6, wherein the
cooling means include at least one Peltier cell integrated in the
base element in the vicinity of the at least one array of SMA
actuating members.
10. An adjustable micro valve according to claim 7, wherein the
cooling means include at least one Peltier cell integrated in the
base element in the vicinity of the at least one array of SMA
actuating members.
11. An adjustable micro valve according to one of the claim 5,
wherein the actuating members are made of TiNi.
12. An adjustable micro valve according to one of the claim 6,
wherein the actuating members are made of TiNi.
13. An adjustable micro valve according to one of the claim 7,
wherein the actuating members are made of TiNi.
14. An adjustable micro valve according to one of the claim 8
wherein the actuating members are made of TiNi.
15. An implantable micro valve having an adjustable opening
pressure comprising: an upper cover having a fluid outlet; a bottom
cover connected to the upper cover thereby defining an interior
chamber, said bottom cover having a fluid inlet; a micro valve
disposed within the interior chamber having a base plate face; and
electrical components and an antenna disposed within the interior
chamber for energizing and controlling the actuation of the micro
valve by telemetry.
16. An implantable pump comprising: an upper cover having a fluid
outlet; a bottom cover connected to the upper cover thereby
defining an interior chamber; a pressurised reservoir disposed
within the interior chamber; a micro valve assembly disposed within
the interior chamber, the micro valve having a base element having:
a base plate face and at least one passage for the flow of fluid;
at least one array of actuating members made of a SMA material
arranged on the base plate face; means for cooling at least one
array of actuating members; and means for heating at least one
array of actuating members; and electrical components and an
antenna disposed within the interior chamber for energizing and
controlling the actuation of the pump by telemetry.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of setting and/or
actuating a multi-stable valve used in fluidic or in micro fluidic
applications. Another object of the invention is an adjustable
multi stable valve for use in medical devices implanted in a human
body.
[0003] More specifically, the invention relates to a micro valve
having at least two stable states at operating temperature. An
opening pressure and a resistance to fluid flow correspond to each
state of the valve. The valve may be actuated non-invasively, by
telemetry for example, with an external device, providing an
adjustable opening pressure valve or alternatively a valve assembly
with adjustable resistance to flow.
[0004] 2. Discussion of the Related Art
[0005] The valve object of the present invention has a wide range
of applications in different fields (medical, hydraulics,
micro-engineering, etc.). For example, in the medical field related
to the treatment of hydrocephalic patients, it is necessary to
install a shunt system that derives the excess of liquid from the
brain to the peritonea or to another cavity of the patient. Some
existing shunt systems comprise an adjustable valve that allows the
surgeon to modify non-invasively the valve opening pressure after
implantation. These existing implantable valves for the treatment
of hydrocephalic patients have successfully shown that the feature
allowing the surgeon to adjust non-invasively the valve opening
pressure after implantation is extremely useful. Nevertheless,
there are some drawbacks associated with devices of this type that
can be summarised as follows:
[0006] These known implants do not provide the user with any
feedback during or after adjustment of the valve opening pressure.
Therefore, it might be necessary to take an X-ray for checking the
valve setting. Furthermore, the valve can be misadjusted by strong
magnetic fields, such as those generated by a permanent magnet
found for example in magnetic resonance imaging devices.
[0007] Finally the existing valves are sometimes blocked due to an
accumulation of bio-substance on the mechanical parts of the valve
mechanism.
[0008] Some other known electromechanical or pneumatic valves
require energy for remaining in one or more working positions and
are not suitable for human or animal implantation due to their size
and/or their lack of tightness.
SUMMARY OF THE INVENTION
[0009] The valve object of the present invention overcomes the
problems exposed above by providing a micro valve having at least
two stable states at operating temperature. The valve according to
the invention does not require energy at rest during normal
operation and is insensitive to magnetic fields by design. Since
the valve setting may be adjusted without mechanical movement of
any parts, the valve is less sensitive to blockage due to an
accumulation of bio substances.
[0010] The actuation concept is based on temperature changes above
and below body temperature. Energy is only required to change the
valve from one state to the other. Valves for the treatment of
hydrocephalic patients, as well as valves for all kind of
implantable pumps constitute major applications of that concept
that may be extended to other fields.
[0011] These and other drawbacks are overcome with a method in
accordance with the present invention for setting and actuating an
implantable valve having the steps of cooling an array of actuating
members made of SMA material to a temperature equal or below the
temperature at which a transformation from austenitic to
martensitic state occurs so that the entire array of SMA actuating
members is either fully or partially in the martensitic state. At
least one of the actuating members corresponding to a
pre-determined opening pressure or resistance to flow is selected.
Each of the actuating members, except the previously selected
members are individually heated to a temperature equal to or above
the temperature at which a transformation from the martensitic
state to the austensitic state occurs.
[0012] These and other drawbacks are also overcome with a micro
valve having a base element with at least one passage for the flow
of fluid. At least one array of actuating members is made of a SMA
material is arranged on the base plate face. The at least one array
of actuating members has a device for cooling one or all of the
actuating members. The at least one array of actuating members has
a device for heating one or all of the actuating members.
BRIEF DESCRIPTION OF THE DRAWINGS AND FIGURES
[0013] Further features and other objects and advantages of this
invention will become clear from the following detailed description
made with reference to the accompanying drawings illustrating in a
schematic and non-limiting way three embodiments of a multi stable
micro valve according to the invention and in which:
[0014] FIG. 1 is a graph showing the typical temperature hysteresis
of shape memory alloy (SMA).
[0015] FIG. 2 is a graph showing the typical stress-strain
characteristics of a shape memory alloy in each of its states.
[0016] FIG. 3 is a schematic perspective top view of a first
embodiment of a micro valve according to the invention.
[0017] FIG. 4 is a bottom perspective view according to the first
embodiment shown at FIG. 3.
[0018] FIG. 5 is cross sectional view of the first embodiment of
the valve shown at FIG. 3.
[0019] FIG. 6 is a perspective top view of a second embodiment of a
micro valve according to the invention.
[0020] FIG. 7 is perspective bottom view of the second embodiment
depicted in FIG. 6.
[0021] FIG. 8 is schematic cross sectional view of the second
embodiment depicted in FIG. 6.
[0022] FIG. 9 is schematic perspective top view of a third
embodiment of a micro valve according to the invention.
[0023] FIG. 10 is a perspective bottom view of the third embodiment
depicted in FIG. 9.
[0024] FIG. 11 is a perspective top view of an implantable assembly
incorporating a valve according to the invention, the top cover
being exploded.
[0025] FIG. 12 is a perspective view of the assembly depicted in
FIG. 11 with the bottom cover exploded.
[0026] FIG. 13 is a bottom perspective view of the assembly shown
at FIGS. 11 and 12.
[0027] FIG. 14 is an exploded perspective view of an implantable
pump embodying a valve according to the invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0028] In the following disclosure, reference will be made to shape
memory alloys, hereafter called SMA material. The properties and
characteristics of such materials are briefly described in the
following.
[0029] SMA material is characterised by reversible metallurgical
phase transformations that are activated either by temperature
change or by induced stress. Below a range of transition
temperature, the material is in the martensitic state, whereas
above that temperature range, the material is in the austenitic
state. The transformation occurs across a range of temperatures
which are commonly named A.sub.s (start) and A.sub.f (finish) for
the transformation from martensitic to austenitic state and M.sub.s
(start) and M.sub.f (finish) for the transformation from austenitic
to martensitic state as referenced in FIG. 1. These transformations
are reversible so that the material may be treated to assume
different shapes in each of the two phases, and can reversibly
switch between the two shapes when transformed from one state to
the other. More commonly, the material is treated to only return to
a shape upon transformation to the austenitic phase a biasing
force, acting against the SMA material returns it to its alternate
shape upon transformation to the martensitic phase.
[0030] Most of the temperature cycles of the SMA materials have a
hysteresis .DELTA.T, as illustrated on the graph of FIG. 1.
[0031] The elastic modulus of the SMA material depends on its
metallurgical state. FIG. 2 shows a typical stress-strain graph of
a SMA material in both states. It appears clearly that the
austenitic state has a higher elastic modulus than the martensitic
state. Upon initial loading, the stress-strain curve is roughly
linear and the Young's modulus corresponds to the slope of the
curve in the initial loading region. For materials tested at
temperatures just above the A.sub.f temperature, if the material is
further deformed beyond this initial loading region, it will
experience a stress-induced martensitic transformation. The point
on the stress-strain curve at which the stress-induced martensitic
transformation begins can be called the M.sub.s.sup..sigma..
[0032] In the martensitic state, the elastic modulus is lower than
in the austenitic state, and the corresponding M.sub.s.sup..sigma.
(in this case, the stress required to rearrange the pre-existing
martensitic phase) is also lower.
[0033] The invention makes use of the change in mechanical
properties (mainly Young's modulus) of an array of actuators in SMA
material when a transition between the two metallurgical states
occurs.
[0034] For medical implantable devices, the SMA material is
preferably chosen within SMA materials having a working temperature
corresponding to body temperature located between M.sub.s and
A.sub.s. In that case, the material is stable in both states at
rest. Heating the material above A.sub.f will transform it into
austenite (higher modulus material). Cooling the material below
M.sub.f will transform it into martensite (lower modulus material).
While the effect is most pronounced with the temperature of use
located between M.sub.s and A.sub.s, the effect can be observed to
some extent at a number of temperatures in the broader range
between M.sub.f and A.sub.f.
[0035] For example TiNi (Nitinol) is a good choice for the
actuating members of a valve according to the invention as it is
biocompatible. Further, TiNi can be manufactured such that body
temperature is located between M.sub.s and A.sub.s. A TiNi material
manufactured to meet this criterion might have the following
characteristics: Martensitic transformation: M.sub.f=24.degree. C.,
M.sub.s=36.degree. C., Austenitic transformation:
A.sub.s=54.degree. C., A.sub.f=71.degree. C., with a hysteresis :
.DELTA.T.about.35.degree. C. Note that the transformation
temperatures for a particular material also change with stress, so
that the temperatures of the starting material must be selected to
appropriately accommodate the variability due to the operating
stresses of the particular application.
[0036] Fine tuning the temperature cycle and the mechanical
properties may be achieved by playing with the chemical composition
and thermomechanical processing of the material.
[0037] As it will be described in detail with reference to the
figures, the micro valve object of the invention comprises an array
of actuators or actuating members made of a SMA material that
interact either directly with the fluid path or with an elastic
mean, the tension of which being modified by the array of SMA
actuators.
[0038] The SMA material is selected to have two stable
metallurgical states at the temperature of use, e.g., body
temperature. The metallurgical state can be changed either by
cooling or by heating the SMA actuator. One of the metallurgical
states has a higher elastic modulus, whereas the other state has a
lower elastic modulus.
[0039] The heating is obtained by circulating a current through or
in the proximity of the SMA material (Joule effect). The cooling is
achieved with a Peltier cell or an array of Peltier cells
integrated in the base plate of the valve, in the vicinity of the
SMA actuators.
[0040] With reference to FIGS. 3, 4 and 5, a first embodiment of a
micro valve with adjustable opening pressure is illustrated.
[0041] The fluid path crosses a base plate 2 having an array of
orifices 3, closed by the free extremity of a corresponding array
of actuating members 1. The base plate 2 is preferably made of a
glass type material like Pyrex for example. The geometry of the
orifices 3 is identical across the array, which ensures that the
resistance to fluid is the same for each single orifice 3. The
array of actuating members 1 comprises, in this embodiment, an
elongated body from which extend perpendicularly elongated
actuating members. Some other configurations are of course
possible. The actuating members 1 are made of SMA material,
preferably TiNi, and their geometry is chosen so that each fluid
path 3 can be considered as closed when the corresponding actuating
member 1 is in the austenitic state and open in the martensitic
state.
[0042] A Peltier cell 4 is integrated in the base plate 2, and
allows, once energised, the cooling of the array of actuating
members 1.
[0043] Each actuating member 1 may be heated individually by
circulating an electrical current through the connectors 5 bounded
to each of the actuating members 1.
[0044] The valve setting is modified in the following manner.
First, the temperature of the array of SMA actuating members 1 is
decreased to a temperature substantially lower than M.sub.s
(preferably below M.sub.f) by energising the Peltier cell 4. This
transforms all or part of the actuating members 1 to the
martensitic state (lower modulus). Then, at least one actuating
member is selected within the array and the temperature of all
actuating members 1 except the previously selected is increased to
a temperature substantially higher than A.sub.s (preferably above
A.sub.f) This is achieved by circulating an electrical current
through the connectors 5 connected to the actuating members 1. Once
the higher temperature is reached, all or part of the actuating
members 1 are in the austenitic state (higher modulus) except the
selected actuating member which remains all or partially in the
martensitic state thus determining the opening pressure of the
valve.
[0045] As an alternative, the array of SMA actuators may be first
heated to a temperature at which an austenitic transformation
occurs and then at least one selected actuating member is cooled
down to a temperature at which a martensitic transformation occurs.
For implementing this alternate method, an array of Peltier cells
is provided. Each Peltier cell forming the array being located in
the vicinity of an actuating member so as to enable the individual
cooling of each actuating member.
[0046] The size and geometry of each actuating member 1 forming the
array can be adjusted for providing different opening pressure
depending on which actuating member remains in the martensitic
state.
[0047] FIGS. 6, 7 and 8 depict another embodiment of a valve with
an adjustable opening pressure. The base plate 2 has only one
orifice 3 through which the fluid may flow. A ball 6 is maintained
in the seat of the orifice 3 with an elastic element like a
flexible flat spring 7 for example. The spring 7 need not be made
of a SMA material.
[0048] An array of SMA actuating members 1 is arranged
perpendicularly to the spring 7 and the free end of each actuating
member 1 interacts with the spring 7. Depending on the
metallurgical state of the SMA actuating members 1, the length of
the spring allowed to move freely is restricted. The force applied
to the ball is determined by the tension of the spring 7 which
varies with the metallurgical states of the actuating members
1.
[0049] A Peltier cell is integrated in the base plate 2 in the
vicinity of the SMA array of actuating members 1. Upon activation,
the Peltier cell cools the array and all the actuating members 1
change to martensitic state. Each of the actuating members 1 may
then be individually heated to a temperature at which an austenitic
transformation occurs. This determines the length of activation of
the spring 7 and therefore the opening pressure of the valve.
[0050] With reference to FIGS. 9 and 10, a third embodiment of a
valve according to the invention is disclosed. This embodiment
provides a valve with an adjustable resistance to flow. A circular
base plate 9 comprises, on its periphery, an array of openings 10
through which a fluid may flow. An array of actuating members 11 is
arranged on the base plate 9 so that the free end of each actuating
member 11 closes a corresponding opening 10 of the base plate. The
SMA actuating members 11 are preferably extending from the center
of the base plate 9 to the periphery of the plate.
[0051] In this embodiment, all the actuating members 11 have the
same geometry but the geometry of the orifices 10 may differ in
order to provide a range of different resistances to flow. A
Peltier cell or an array of Peltier cells is integrated in the base
plate 9, preferably in the centre of the base plate so as to enable
cooling of the complete array of SMA actuating members 11.
[0052] The setting or the actuating of the valve is similar to what
has been disclosed in reference to the first embodiment at FIG. 3
to 5.
[0053] FIGS. 11, 12 and 13 illustrate an implantable valve with
adjustable opening pressure. The implantable valve comprises a
valve assembly 12 according to one of the first or second
embodiment disclosed above. A top cover 13 having a fluid outlet 14
is adapted to receive the valve assembly 12. An antenna 17 as well
as the necessary electronic components 18 to power and control the
valve assembly by telemetry are integrated on the bottom of the
base plate of the valve assembly 12. A bottom cover 15 having a
fluid inlet 16 and a leak tight compartment 19 for protecting the
electronic components closes the structure.
[0054] The user may then power the assembly by telemetry and select
non-invasively the opening pressure from outside the body by
firstly cooling the SMA array of actuating members 11 and then
selectively heating by Joule effect one or more actuating members
11. The electronic components 18 integrate a feedback mechanism
that can be used to confirm that the correct actuating member 11 or
array of actuating members have been heated.
[0055] A valve according to the invention may also be used in an
implantable drug delivery pump. A few existing adjustable
implantable pumps allow the user (patient and/or doctor) to select
non-invasively a flow rate of chemicals to inject, due to an
external programming unit. The existing devices can be divided in
two main categories: the active or passive pumping mechanisms. In
the first case, a battery energises a pump that regulates the flow
rate of chemicals. In the second case, a pressure reservoir
"pushes" the chemicals out of the pump. The later concept is very
elegant since the pumping does not require energy. Nevertheless,
the regulation of the fluid flow is ensured by a valve, the opening
of which depends on the power delivered to the valve. Therefore, a
battery is still required.
[0056] Due to a valve according to the invention, when used in an
implantable adjustable pump, the energy consumption problem is
solved, since energy is only required to change the flow setting of
the pump.
[0057] In the current products, energy is required continuously to
keep the valve open. An adjustable passive pressurised pump
embodying a valve according to the invention will now be disclosed
with reference to FIG. 14.
[0058] The implantable pump comprises a pressurised reservoir 20
that contains the drug substance or other fluid to administrate. A
valve assembly 21 as described with reference to the third
embodiment shown in FIGS. 9 and 10 constitutes the adjustable flow
resistance valve of the pump. The bottom of the base plate of the
valve assembly 21 incorporates electronic components and an antenna
that are used to power and control the valve non invasively by
telemetry. A leak tight cover 22 protects the bottom face of the
base plate and the electronics components, avoiding contact with
the pressurised liquid contained in the reservoir 20. A top cover
23 having a fluid outlet 24 closes the structure.
[0059] The user may select the resistance of the valve from outside
with a dedicated reading unit and therefore regulates the outflow
of chemicals contained in the pressurised reservoir.
[0060] Many advantages are achieved with a valve according to the
invention. Firstly, as the valve has multi stable states, energy is
only required to switch from one state to the other. No energy is
needed to maintain a selected state. Each state can either
correspond to a selected opening pressure or to a flow resistance,
depending on the application.
[0061] Second, the valve settings can be adjusted without a
movement of any part. Only the elastic modulus of the material is
modified and therefore the valve is less sensitive to blockage by
clogs and other bio-substances.
[0062] The energy required is the energy needed to power a Peltier
cell, and the energy for heating the actuating members. This energy
can be provided to the implantable device by telemetry avoiding the
use of batteries.
[0063] For medical applications, and more particularly for
implantable adjustable valves or pumps as previously described, the
choice of the SMA material is of importance. It must be chosen from
the SMA materials that have two stable states at a temperature in
the vicinity of the body temperature. Furthermore, the SMA material
ideally should fulfill the following conditions.
M.sub.s<T<A.sub.s where T is the temperature of the human
body and an hysteresis .DELTA.T, comprised between 10 and 40
degrees centigrade. TiNi (Nitinol) is a material that fulfills
these requirements and which is also biocompatible.
[0064] It will be appreciated by persons skilled in the art that
the present invention is not limited by what has been disclosed
above, particularly with regards to the field of use of the valve,
which may be integrated in other fluidic devices. Furthermore, the
present invention may include combinations and sub-combinations of
the various features disclosed as well as modifications and
extensions thereof which fall under the scope of the following
claims.
* * * * *