WO2014134659A1

WO2014134659A1 - Pools of liquid electrode tester

Info

Publication number: WO2014134659A1
Application number: PCT/AU2014/000153
Authority: WO
Inventors: Arthur Lowery; Brody PAYNE; Micah Atkin; Mike Smith
Original assignee: Monash University
Current assignee: Monash University
Priority date: 2013-03-08
Filing date: 2014-02-20
Publication date: 2014-09-12
Anticipated expiration: 2015-09-08

Abstract

A test system (300) comprises an electrode array device (100) comprising a plurality of electrodes (104) mounted on a support (102). Each electrode has an electrical input adapted to receive an electrical stimulus signal. A further component (200) of the system has a housing (202) with an interior volume (203)which is adapted to receive the electrode array device (100) such that the electrode array device is maintained in position with the plurality of electrodes extending into the interior volume. The apparatus comprises a plurality of wells (204) located within the interior volume of the housing, each well having an opening positioned to receive a corresponding one of the plurality of electrodes, and further having an inner surface comprising side walls (206) extending from the opening and a base (208). A conductive element (210) is positioned within each well. The wells are isolated from one another, and a quantity of electrically conductive fluid (302) is disposed within each well. The electrode array device (100) is received within the housing such that each of the plurality of electrodes projects into a corresponding well and an exposed portion of the electrode is immersed in the electrically conductive fluid.

Description

POOLS OF LIQUID ELECTRODE TESTER

FIELD OF THE INVENTION

[0001] The present invention relates to electrical testing and related activities, and more particularly to a system, apparatus and method for testing or altering the properties of conductive electrodes, especially fragile electrodes, without direct mechanical contact. Embodiments of the invention may find particular application in the life sciences in which sensitive, fragile and miniaturised electrodes are designed to be directly introduced into living biological systems.

BACKGROUND TO THE INVENTION

[0002] Neural implants are a class of devices designed to communicate with the nervous system of a human or animal. A common type of implant comprises electronic components interfaced with an array of small electrodes. The electrodes may take the form of projecting conductive 'needles', which are implanted directly into living tissue of the human or animal subject, in order to interface directly with healthy neurons in the body.

[0003] Applying an electrical stimulus, i.e. a current or voltage, to an electrode creates an interaction with the associated neurons, and can be used to bypass damaged areas of the brain, or other parts of the nervous system, to restore function, block pain, or prevent seizures, amongst an increasing number of applications.

[0004] An early widely-used neural prosthetic was the cochlear hearing implant, which restores a sense of sound to people with severe hearing impairments. More recently, a range of implants for other purposes, such as preventing seizures in patients with epilepsy and Parkinson's disease, have been developed. Spine implants have been developed for pain control, while other devices stimulate peripheral nerves and muscles. [0005] However, emerging applications, such as 'bionic vision', are placing increasing demands upon electrode technologies. To deliver on the full promise of neural prosthetics, it will be necessary to develop smaller implantable devices, with large numbers of more-densely packed electrodes.

[0006] Testing of these devices prior to implantation will be essential, particularly in view of the considerable inconvenience and risk to patients if defective devices must be removed and replaced.

[0007] Due to the small size, fragility, sensitivity, and requirements to avoid contamination of electrodes or other surfaces, providing for safe, effective and efficient testing of electrode ray devices presents new challenges. There is, accordingly, scope for the development of new, improved and/or alternative systems, apparatus and methods for electrode testing. It is an object of the present invention to provide such a system, apparatus and method.

SUMMARY OF THE INVENTION

[0008] In one aspect, the invention provides a system comprising:

an electrode array device comprising a plurality of electrodes mounted on a support, each electrode having an electrical input adapted to receive an electrical stimulus signal;

an apparatus having a housing with an interior volume, the housing being adapted to receive the electrode array device such that the electrode array device is maintained in position with the plurality of electrodes extending into the interior volume,

wherein the apparatus comprises a plurality of wells located within the interior volume of the housing, each well having an opening positioned to receive a corresponding one of the plurality of electrodes, and further having an inner surface comprising side walls extending from the opening and a base, and a conductive element positioned therein

wherein the wells are isolated from one another; and wherein a quantity of electrically conductive fluid is disposed within each well, and the electrode array device is received within the housing such that each of the plurality of electrodes projects into a corresponding well and an exposed portion thereof is immersed in the electrically conductive fluid.

[0009] Advantageously, systems embodying the invention provide a plurality of isolated 'pools' of conductive fluid, each of which is arranged to receive a corresponding electrode, and provide electrical conduction between the electrode and a conductive element disposed within the pool. This enables all of the electrodes within the array to be simultaneously available for testing, without applying any mechanical force, or indeed any form of direct physical contact, between each electrode and a test pad or other conductive element. In use, the electrical inputs of the electrodes may be driven under the control of suitable electrical test apparatus, the resulting signals may be detected at the conductive elements within each well, and accordingly the effectiveness of each electrode in conducting the stimulus signals may be measured. Preferably, this process may be automated, such that individual tests may be performed rapidly, and testing may be performed continuously, or repeatedly, over an extended period of time in order to determine the detailed behaviour of the electrodes, and the stability of their performance.

[0010] In some embodiments, the electrically conductive fluid may be a liquid, for example a sterile aqueous solution comprising a suitable electrolyte.

[0011] In alternative embodiments, the fluid may be an electrically conductive gel.

[0012] More generally, the term 'electrically conductive fluid', as used in relation to embodiments of the present invention, encompasses any suitable deformable conductive medium that will not cause damage to the electrodes upon insertion or removal. This may include liquids, gells, biological or cellular materials, and small conductive particles. [0013] Ideally, the fluid is highly conductive, hypoallergenic, and

bacteriostatic. In the case of conductive gels, it is desirable that the fluid be water-soluble.

[0014] Following testing, therefore, electrode arrays shown to have satisfactory performance may be readily washed, dried and sterilised for implantation.

[0015] The system may further include an electrical test arrangement comprising apparatus configured to apply an electrical stimulus signal to one or more of the plurality of electrodes, and apparatus configured to be conductively coupled to one or more of the conductive elements within the plurality of wells, to detect the generation of electrical signals at a corresponding one or more of the electrodes.

[0016] Alternatively, an electrical test arrangement may comprise apparatus configured to apply an electrical stimulus signal to one or more of the conductive elements within the plurality of wells, and apparatus configured to be conductively coupled to one or more of the plurality of electrodes, to detect the generation of electrical signals at a corresponding one or more of the electrodes.

[0017] Embodiments of the system may also be employed in other applications, such as performing in-vitro tests or experiments on fluid materials contained within the wells, depositing material on the surface of the electrodes (e.g. electroplating) or removing material from the surface of the electrodes (e.g. electroetching).

[0018] In another aspect, the invention provides a method employing an electrode array device which comprises a plurality of electrodes mounted on a support, each electrode having an electrical input adapted to receive an electrical stimulus signal, the method comprising:

providing an apparatus having a housing with an interior volume, the housing being adapted to receive the electrode array device such that the electrode array device is maintained in position with the plurality of electrodes extending into the interior volume, wherein the apparatus comprises a plurality of wells located within the interior volume of the housing, each well having an opening positioned to receive a corresponding one of the plurality of electrodes, and further having an inner surface isolating the well from adjacent wells, the inner surface comprising side walls extending from the opening and a base, and further comprising a conductive element positioned therein;

disposing a quantity of an electrically conductive fluid within each well; positioning the electrode array device within the housing such that each of the plurality of electrodes projects into a corresponding well and an exposed portion thereof is immersed in the electrically conductive fluid; and either:

applying an electrical stimulus signal to one or more of the plurality of electrodes, and detecting one or more corresponding electrical signals conveyed to one or more of the conductive elements within the plurality of wells via the electrically conductive fluid; or

applying an electrical stimulus signal to one or more of the conductive elements within the plurality of wells, and detecting one or more corresponding electrical signals conveyed to one or more of the plurality pf electrodes via the electrically conductive fluid.

[0019] In another aspect, the invention provides an apparatus for contactless application of test signals to a plurality of electrodes in an electrode array, the apparatus comprising:

a housing having an interior volume, the housing being adapted to receive a corresponding electrode array device such that the electrode array device is maintained in position with an associated plurality of electrodes extending into the interior volume;

a plurality of wells located within the interior volume of the housing, each well having an opening positioned to receive a corresponding one of the plurality of electrodes, and further having an inner surface comprising side walls extending from the opening and a base; and a plurality of conductive elements, each conductive element being positioned within a corresponding one of the plurality of wells,

wherein the wells are isolated from one another, in use, such that a quantity of an electrically conductive fluid may be disposed independently within each well, the quantity being sufficient to contact the corresponding electrode projecting into the well and the corresponding conductive element.

[0020] Further features, benefits and advantages of embodiments of the invention will be apparent from the following description, which is provided by way of example only, without limitation to the scope of the invention as described in the preceding statements, or defined in the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the invention will now be described with reference to the accompanying drawings, in which like reference numerals refer to like features, and wherein:

Figure 1 illustrates an exemplary electrode array device suitable for testing in accordance with embodiments of the invention;

Figures 2(a) and 2(b) show schematically top and cross-sectional views of an apparatus for electrical testing of the electrode array device of Figure 1 ;

Figure 3 shows schematically a cross-sectional view of a system configured for testing of an electrode array device; and

Figure 4 is a flowchart illustrating a method of testing an electrode array device according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0022] Figure 1 illustrates an exemplary electrode array device 100 for which electrical testing of electrodes may be required. The device 100 comprises a rigid support 102, which may be made of a ceramic or other suitable biologically inert material. Projecting from the support 102 is an array comprising a plurality of electrodes 104.

[0023] In the exemplary device 100, the array 104 comprises around 60 electrodes, each of which may be approximately 2 millimetres in length, having an exposed conductive tip of around 10 micrometres in length, and spaced apart by approximately 0.5 millimetres. However, it will be appreciated that these dimensions are exemplary only, and that electrode arrays for use in different applications may have a range of different configurations and dimensions.

[0024] In a typical application, each electrode may be configured to deliver a current approximately in the range of 5 to 50 microampere for stimulation of adjacent neurons. Again, it will be appreciated that the precise level of electrical stimulation to be delivered by each electrode may vary depending upon the application.

[0025] A connecting cable 106 is provided to carry signals from which the electrical stimulus signals to be delivered by each electrode 104 may be derived. The support structure 102 may enclose electronic processing components for decoding signals received via the cable 106, and generating driving stimulus signals to each electrode 104. Advantageously, such a configuration enables the number of separate conducting wires making up the connecting cable 106 to be reduced, i.e. such that it is not necessary to provide a separate connection to every individual one of the electrodes within the array 104. For example, signals corresponding to stimuli to be applied by the plurality of electrodes 104 may be encoded and transmitted via the cable 106, with electronics within the support 102 performing the necessary decoding functions to determine which electrodes the stimuli are to be directed to, along with the corresponding magnitude and/or waveform of the stimulus signals.

[0026] Figures 2(a) and 2(b) show, respectively, top and cross-sectional views of an apparatus for electrical testing of the electrode array device 100 shown in Figure 1. The test apparatus 200 comprises a housing 202 which is open at the top, and encloses an interior volume 203. Within the interior volume, there is located a plurality of wells 204. Each well 204 has an upper opening which is positioned to receive one of the plurality of electrodes projecting from the electrode array device 100. As shown in Figures 2(a) and 2(b), the wells 204 are square, however other shapes, such as circular or hexagonal wells, could alternatively be used.

[0027] As shown, each well 204 has an upper opening, and is otherwise enclosed and isolated from adjacent wells by side walls 206 and a closed base 208. Within each well there is positioned a conductive element 210, which may be, for example, an inert metallic or conductive polymer contact. A conductor 212 connects each conductive element 210 to a point at an exterior surface of the housing 202.

[0028] The test apparatus 200 also comprises pinholes 214 formed through the housing 202 and the base 208 of each well 204. The pinholes 214 enable fluids, such as the conductive fluids described below with reference to Figure 3, to be injected into each well under increased pressure applied from below the housing 202. Additionally, fluids and/or air bubbles within the wells 204 may be extracted by application of reduced pressure. The pinholes 214 are sufficiently small that, in the absence of an adequate pressure difference between the exterior of the housing 202 and the interior of the wells 204, surface tension prevents the flow of fluids via the pinholes. Accordingly, each well 204 remains effectively isolated from adjacent wells, and from the exterior of the housing 202.

[0029] According to different embodiments of the invention, the pinholes 214 may be optional. For example, in alternative arrangements fluids may be injected into, and/or extracted from, each of the wells 204 via the upper openings, e.g. using one or more pipettes. It will be appreciated that various arrangements and mechanisms for injecting and extracting fluids from the wells 204, such as would be apparent to persons skilled in the art, are within the scope of the invention. [0030] Figure 3 shows schematically a cross-sectional view of a system 300 in which the electrode array device 100 is positioned within the test apparatus 200 for testing of the electrode array 104.

[0031] As shown, the housing 200 is formed such that the electrode array device 100 may be received snugly within the upper opening to the interior volume 203, in which position each of the electrodes 104 projects into a corresponding one of the wells 204.

[0032] Within each one of the wells 204 there is disposed a suitable electrically conductive fluid 302, such as a sterile aqueous electrolyte solution, or a suitable electrically conductive gel. The electrically conductive fluid 302 thus contacts the conductive tip of each electrode 104, and the corresponding conductive element 210 within the well 204. Any electrical signal generated at the electrode tip is conveyed via the conductive fluid 302 and can be detected at the conductive element 210 and conveyed to the exterior of the housing 200 via the conductor 212.

[0033] In the system 300, an electrical connector 304 is provided, to which the test apparatus 200 is fitted, whereby each conductor 212 contacts a

corresponding conductor (not shown) of the connector 304. A cable 306 conveys detected signal from the connector 304, for example to a suitable test and measurement apparatus. In some embodiments, the connector 304 may contain detection and processing electronics, for detecting signals received from each electrode of the array 104, and generating a corresponding processed signal for transmission via the cable 306. Advantageously, this arrangement may enable the very large number of individual electrode signals to be transmitted via a compact cable 306, rather than requiring an individual conductor within the cable corresponding with each of the conductive elements 210.

[0034] Figure 4 shows a flowchart 400 illustrating a method of testing an electrode array device 100 using the system 300 shown in Figure 3. [0035] At step 402, the test apparatus 200 is provided, and at step 404 the conductive fluid (e.g. liquid or gel) is disposed within each of the wells 204.

[0036] At step 406 the electrode array device 100, i.e. the device under test (DUT), is positioned within the test apparatus housing 200.

[0037] At step 408 stimulus signals are applied to one or more of the electrodes 104. At step 410, corresponding detected signals are recorded, i.e. as gathered by the conductive elements 210, conveyed via the conductors 212, and transmitted back to suitable test apparatus via the connector 304 and cable 306.

[0038] Step 412 determines whether more tests are to be conducted. For example, it may be required to apply stimulus signals to one or more further electrodes of the array 104. Alternatively, it may be desired to apply different stimulus signals to the same electrodes as previously tested. As yet another possibility, it may be desired to apply the same stimulus signals to the same electrodes, continuously and/or repeatedly, over an extended period of time, in order to test the stability and/or degradation in performance of the electrodes 104.

[0039] As will be appreciated, the tests at steps 408 and 410 may be conducted under computer control, i.e. with a computer program generating and transmitting the stimulus signal commands via the cable 106, and receiving the corresponding detected results via the cable 306, and recording the detected signals over the course of the test. Additionally, a computer-controlled test may be programmed to adapt the testing, to generate alerts, and/or to halt the test, depending upon the results received in response to stimulation of individual electrodes. For example, if any electrode fails to operate within the desired specifications, the test may be halted, and the computer may display a message indicating that the DUT has failed. [0040] In an alternative arrangement, stimulus signals may be applied to the conductive elements 210 via the conductors 212, and corresponding signals detected at the electrodes 104.

[0041] As will be appreciated, a variety of different test scenarios may be implemented using the system 300 shown in Figure 3. The setup of the system 300, and the appartus 200, may also employed in other applications, such as performing in-vitro tests or experiments on fluid materials contained within the wells 204, depositing material on the surface of the electrodes 104 (e.g.

electroplating) or removing material from the surface of the electrodes 104 (e.g. electroetching). Such alternative test configurations and/or applications, as well as other variations and combinations of features which are apparent to persons skilled in the relevant art, are encompassed by the present invention, insofar as it is defined in the claims appended hereto.

Claims

CLAIMS:

1. A system comprising:

wherein the apparatus comprises a plurality of wells located within the interior volume of the housing, each well having an opening positioned to receive a corresponding one of the plurality of electrodes, and further having an inner surface comprising side walls extending from the opening and a base, and a conductive element positioned therein,

wherein the wells are isolated from one another, and

wherein a quantity of electrically conductive fluid is disposed within each well, and the electrode array device is received within the housing such that each of the plurality of electrodes projects into a corresponding well and an exposed portion thereof is immersed in the electrically conductive fluid.

2. The system of claim 1 wherein the electrically conductive fluid is a liquid.

3. The system of claim 1 wherein the electrically conductive fluid is a gel.

4. The system of claim 1 further including an electrical test arrangement comprising apparatus configured to apply an electrical stimulus signal to one or more of the plurality of electrodes, and apparatus configured to be conductively coupled to one or more of the conductive elements within the plurality of wells, to detect the generation of electrical signals at a corresponding one or more of the electrodes.

5. The system of claim 1 further including an electrical test arrangement comprising apparatus configured to apply an electrical stimulus signal to one or more of the conductive elements within the plurality of wells, and apparatus configured to be conductively coupled to one or more of the plurality of electrodes, to detect the generation of electrical signals at a corresponding one or more of the electrodes.

6. A method employing an electrode array device which comprises a plurality of electrodes mounted on a support, each electrode having an electrical input adapted to receive an electrical stimulus signal, the method comprising:

disposing a quantity of an electrically conductive fluid within each well; positioning the electrode array device within the housing such that each of the plurality of electrodes projects into a corresponding well and an exposed portion thereof is immersed in the electrically conductive fluid; and

either

7. The method of claim 6 wherein the apparatus comprises pinholes formed through the housing and the base of each well, and the step of disposing the quantity of the electrically conductive fluid within each well comprises injecting the electrically conductive fluid into each well via a corresponding one of the pinholes.

8. An apparatus for contactless application of test signals to a plurality of electrodes in an electrode array, the apparatus comprising:

a plurality of wells located within the interior volume of the housing, each well having an opening positioned to receive a corresponding one of the plurality of electrodes, and further having an inner surface comprising side walls extending from the opening and a base; and

a plurality of conductive elements, each conductive element being positioned with a corresponding one of the plurality of wells,

9. The apparatus of claim 8 further comprising a plurality of conductors arranged to convey signals between each one of the conductive elements and an exterior of the housing.

10. The apparatus of claim 7 comprising pinholes formed through the housing and the base of each well, for injection of electrically conductive fluid into each well and/or extraction or air or electrically conductive fluid from each well.