CA1184251A

CA1184251A - Probe for medical application

Info

Publication number: CA1184251A
Application number: CA000402295A
Authority: CA
Inventors: Otto Prohaska
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-05-07
Filing date: 1982-05-05
Publication date: 1985-03-19
Also published as: EP0064970A3; DE3272121D1; US4682602A; ATA202981A; AT369254B; EP0064970A2; EP0064970B1; JPS57192543A; JPH0310327B2

Abstract

PROBE FOR MEDICAL APPLICATION

Abstract of the Disclosure A medical probe has a transducer or electrode en-closed in an insulating cover which defines a chamber with a substrate. A medium in said chamber communicates via a hole in the cover with material under test.

Description

PROBE FOR MEDICAL APPLICATION
. .

Background This invention is concerned with a medical probe for the use of registering and influencing tissue ac-tivities. Especially meaningful are the thin film probes, called electrode probes or transducer probes, used in medical research as well as in human medicine in order to deter~ine or to influence electrical activities of the tissue, ~etabolic activities, blood flow, ion and ~olecu-lar changes, etc.
Thin film probes are qualified in particular for multiple recordings because of their possible variation in design and dimension tO. Prohaska, F. Pacha, P. Pfundner, H. Petsche: A-16-fold se~i-microelectrode for intracortical recording of field potentials, Ælec-troenceph~ Clin. Neurophysiol. 47, 629-631, 1979).
One previously known medical electrode, described by AT-PS 342 189, consists of a non-conducting body that carries on one end a contact electrode which is connected to a lead within the non-conducting body. In addition, a throw away enclosure of non-conducting material is mounted around the individual reusable electorde. Within the cover is a cavity which is bordering on the contact electrode as well as on the outer area by at least one aperture in the throw awav enclosure and is filled by a viscous electrolyte.
,~
f ~

2 --The problems in this res~ect lie in the direct con-tact between tissue and metal or intermetallic compound electrodes and/or transducers which cause some serious disadvantages-a) the electrode impedance and electrode area (H.J. Vetter: Elektrochemische Kineti~, Springer Verl.
Berlin, 1961) and, therefore, limits the technical minia-turi~ation possibilities of the electrode, b) polarographic recordings (I.M. Kolthoff, J.J. Lingane: Polarographie, Intersci, Publ. NY., 1952) cause a current flow througil the tissue which irritates or injures the tissue, c) the extracellular ion and molecular concen-tration is only recordable under certain conditions which, unfortunately, seldom exist, d) ion concentration changes of-ten influ-ence heavy potential recordings within the tissue; for instance: Cl- concentration changes cause the electrode potential change of an Ag/AgCl electrode.
Due to the invention of this probe, the disadvan-tages are diminished because at least one electrode or transducer (2) is enclosed by an insulating cover (6) that is supported by the insulating substrate (7, 11), whereby the thickness o~ the cover is in the range of 0.5 ~m up to lOJum - preferably 3 llm - forming a chamber (1) which is filled by a gaseous and/or fluid and/or solid medium

(3) and which is up to 30,um high (5), having at least one aperture (4), in connection with which the insulating cover is comprised of at least one of the materials SiO, Six~ Si3~4, SioxN4~ Tio2~ Ta20s or similar materials which have mechanical or electrical qualities comparable to the above-mentioned materials.
The main new effects are obtained by the chambers (1), containing a material that establishes the contact between electrode or transducer and the material under test (e.g., tissue) as well as by the multiple vision of L

the chambers on a probe where miniaturization, cau~ed b~
the use of a thin film technology, is of main importance.
For the purpose of illustrating the invention, there is shown in the drawings a orm which is presently pre-ferred; it being unc3erstood, however, that this invention is not limited to the precise arrangements and instrumen-talities shown.
Figures 1, 2 and 3 show three possible types of chambers.
Figures 4, 5, 6 and 7 show the cross-section of different types of probes.
Detailed Description Figure 1 shows an elevated chamber (1) which is called a "thin film buffer chamber". Chamber (1) is de-fined by a thin insulating cover layer (6) which deter-mines the outer shape of the thin film buffer chamber (1).
Layer (6) is 0.5/um to 10~um thick, preferably 3 ~m, and is made from at least one of the following materials: SiO2, Six~ Si3N4~ sioxM4l T12~ Ta20s or similar materials which have comparable mechanical and electrical qualities.
Iayer (6) is directly supported on the insulating sub-strate (7) in such a way that it encloses at least one electrode or transducer (2).
Layer (6) has at least one aperture (4) which com-municates medium (3) with the material under test (9)~
In doing this, a new result was obtained: the aperture

(4) represents now the actual electrocle or transducer of the probe in formin~ the direct connection to the material under test (9), enabling a pointli~e, local recording or influence. On the other hand, the metal or metal compound electrode (2) which were previously determining the qual ities of the probe can be made much larger now since they are no longer in direct contact with the material under test (9) but only indirectly by means of the medium (3) within the thin film buffer chamber (1). In this way, the recordin~ disturbances caused by the electroc3e impedances can be reduced up to 1000 times.

The proerty and shape of the insualting substrate (7) is widely variable. It can be stiff or pliable, round, uneven or plane, flat, needle-shaped or cylindrical, etc.
Figure 2 shows another possible type of thin film buffer chamber (1) where the chamber shape is obtained by etchinq a recess (10) into the substrate (7). The probe is otherwise the same.
Figure 3 demonstrates the chamber construction in "sandwich design" where the recess (12) is etched into the insulation layer (11) which is supported by the substrate (7). In both versions of Figures 2 and 3, the recesses (10) or (12) are covered by a thin insulation layer (6~ in which the aperture (4) is etched. The probe of Figure 3 is otherwise the same.
The advantages of a thin film version, using thin film technology methods for production, result in the pos-sibility of the very precise arrangement of the thin film chambers (1) within a very small area next to or above each other in an arbitrary number. This is extremely im-portant for the practical application because the thin film version enables the exact correlation between record-ing or influence value and the architectronic of the tis sue. ~ue to this precision as well as the multiple ar-rangement of the electrode and transducer areas, a new result is achieved - a connection between different ac-tivities and parameter changes of the tissue can be ex-hibited and a spatial resolution of the above-mentioned processes can be demonstrated, yielding completely new results.
The medium (3) within the thin film buffer chamber (1) determines the recordable or influencable parameters.
The medium (3) can consist of gaseous and/or liquid and/or solid material, for instance an electrolyte or an ion exchanger or a combination of both. Just as important for the recording or influencing mode is the selection of the electrode or transducer materials (2), which may be a precious metal, preferably ~olcl or platinum, or intermetal-lic eompounds or metal salts, the most suitable bein~
Ag/AgCl. They could also be realized as a thermocouple or a resistance thermometer or in such a way so that at least two of the eleetrode or transducer (2) form an electro-chemieal cell together with the medium (3). In doing this, an essentially new result is yieldec]: the eurrent, caused by polarographic recordings, flows within the "thin film buffer ehamber" (1) and does not influenee the tissue aetivity in an undesired way.
One possible realization of the thin film buEfer eha~ber probe is shown in Figure 4. Thereby, the insulat-ing substate (7), due to easy applieation or performanee, might be mounted on an additional insulating and/or eon-dueting supplementary substrate (20), preferably supported on an insulating carrier (13) on whieh eonduetors (14) are arranged. The eonduetors (8) on the insulating substrate (7) are eleetrieallv connected (15) with the conductors (1~) on the earrier (13). In order to guarantee a simple, fast and reliable eleetrical eontaet to the eonductors (14) and (8) and therwith to the eleetrode or transdueer (2) within the thin film buffer ehambers (1), eontaet plugs (16) are mounted on the insulating earrier (13) in sueh a way that they are eonneeted eleetrically (19) with the conductors (14). By appropriate casting of the described arrangement with insulating materials (17), preferably synthetic plastic resin or the like, a container (18) is formed by the insulating material (17) and the insulating suhstrate (7) on top of which the thin film buffer eham-bers (1) are situated. The container (18) is open upward-ly and can be sealed arbitrarily. This type of process is especially suitable for in~estigations of tissue cultures, which are placed into the container (18). The probe is otherwise the same.

~ nother possible realization of the thin film buffer chamber probe is shown in Figure 5 by a cross-section.
The insulating substate (7) has a needle-like shape. The insulating substrate (7) is supported on an insulating and/or conducting additional substrate (20) which has the same needle-like shape as the insulating substrate (7).
In doing this, tissue damages are prevented. By the in-sulating material (17), the non-insulated parts of the conductors (8) and (14) are poured in as well as the electrical connections (15) and (19). The probe is other-wise the same.
A further possible realization is shown in Figure 6.
The insulating substrate (7) or the insulating and/or con-ducting additional substrate (20) has a cylindrical shape.
~ll other features are the same as those described in connection with Figure 5.
Figures 5 and 6 show probe types which are especially suitable for investigation or the influencing of tissue areas located deeper within the body, i.e., deep brain structures, subcutaneous tissue parts, etc.
A variation of the probe in Figure ~ is the probe type shown in Figure 7. By embedding the described probe suitably in insulating material (17), this insulating material (17) forms containers (18) which are open in the upward direction, whereby the apertures (~) of -the cham-bers (l) are kept free.
The present invention may be embodied in other spe-cific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

- 7 -

1. A medical probe especially constructed for registering or influencing tissue activities comprising an insulating substrate; an electri-cal conductor supported by said insulating substrate and insulated with respect to material to be tested; an electrode or transducer supported by said insulating substrate and electrically connected to said electrical conductor; a thin insulating cover layer supported on said insulatng substrate and forming a chamber with said insulating substrate; and means for elec-trically connecting said electrical conductor to registering or influencing circuitry, said electrode or transducer being disposed within the chamber, the chamber being adapted to be filled with a medium for electrically con-necting said electrode or transducer and the material to be tested, the chamber having at least one aperture for providing communication between the medium and the material to be tested.

2. A probe in accordance with claim 1 wherein the chamber is filled with a medium selected from the group consisting of an electrolyte and an ion exchanger in a gaseous, liquid or solid form.

3. A probe in accordance with claim 1 wherein said cover layer is made from a material selected from the group consisting of SiOx, Si3N4, SiOyNz, TiO2, and Ta2Os, x being greater than or equal to 1 and less than or equal to 2, y being greater than 0 and less than 2, and z being greater than 0 and less than 1.33.

4. A probe in accordance with claim 1 wherein the chamber is an indentation on a surface of the insulating substrate, said cover layer being juxtaposed to an open side of said indentation.

5. A probe in accordance with claim 1 wherein the electrode or transducer is made of a material selected from the group consisting of gold, platinum, intermetallic compounds, semi-conductor materials, and metal salts.

6. A probe in accordance with claim 1 including a second electrode or transducer disposed within a second chamber.

7. A probe in accordance with claim 6 including an electrical insulator material supporting electrical contact members, each electrical contact member being electrically coupled to one of said electrodes or transducers.

8. A probe in accordance with claim 1 wherein the probe is embedded in an electrical insulating material having an opening aligned with said first-mentioned aperture.

9. A probe in accordance with claim 1 wherein said insulating substrate and an additional substrate supporting the insulating substrate are each needle-shaped.

10. A probe in accordance with claim 1 wherein said insulating substrate has a cylindrical shape and is closed at one end.

11. A probe in accordance with claim 1 wherein the cover layer has a thickness of 0.05 µm to 10 µm.

12. A probe in accordance with claim 1 wherein the chamber has a height of no greater than about 30 µm.

13. A probe in accordance with claim 1 wherein the aperture has a diameter which is substantially less than the dimensions of the chamber.

14. A medical testing probe comprising an electrode or trans-ducer; a thin insulating non-metallic cover layer enclosing said electrode or transducer; an electrical insulating substrate juxtaposed to said cover layer; and an electrical conductor for electrically connecting said electrode or transducer to registering or influencing circuitry, said cover layer forming a thin buffer chamber with said insulating substrate, the chamber being adapted to be filled with an electrically conducting medium, said electrode or transducer being substantially thinner than the height of the chamber, said chamber having at least one aperture for providing communication between the medium and material under test.

15. A probe in accordance with claim 14 wherein the chamber is filled with a medium selected from the group consisting of an electrolyte and an ion exchanger in a gaseous, liquid or solid form, and wherein said cover layer is made from a material selected from the group consisting of SiOx, Si3N4, SiOyNz, TiO2, and Ta2O5, x being greater than or equal to 1 and less than or equal to 2, y being greater than 0 and less than 2, and z being greater than 0 and less than 1.33.

16. A probe in accordance with claim 14 wherein the cover layer has a thickness of 0.5 µm to 10 µm.

17. A probe in accordance with claim 14 wherein the chamber has a height of no greater than about 30 µm.

18. A probe in accordance with claim 14 wherein the aperture has a diameter which is substantially less than the dimensions of the chamber.