Bioresorbable silicon electronics for transient implants

Patent metadata

Field	Value
Publication number	US-10925543-B2
Application number	US-201615349525-A
Country	US
Kind code	B2
Filing date	Nov 11, 2016
Priority date	Nov 11, 2015
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

Provided are implantable and bioresorbable medical devices comprising a bioresorbable substrate and an electronic circuit supported by the bioresorbable substrate. The electronic circuit comprises a membrane of silicon having a thickness less than or equal to 5 μm and an array of dissolvable electrodes, wherein the dissolvable electrodes are formed from the membrane of silicon. The electronic circuit is configured to conformally contact a biological tissue and electrically interface with biological tissue during use. The silicon may be highly doped to provide the requisite characteristics for electrically interfacing with biological tissue, and may be further used to form other components of the electronic circuit, including back-plane transistors electrically connected to the electrode array.

First claim

We claim:

1. An implantable and bioresorbable medical device comprising:
a bioresorbable substrate;
an electronic circuit supported by said bioresorbable substrate, wherein said electronic circuit comprises a membrane of silicon (Si) having a thickness less than or equal to 5 μm;
an array of dissolvable electrodes, wherein said dissolvable electrodes are formed from said membrane of silicon; and
wherein said electronic circuit is configured to conformally contact a biological tissue and electrically interface with the biological tissue during use.

2. The implantable and bioresorbable device of claim 1 , wherein said dissolvable electrodes are configured to undergo hydrolysis upon contact with a biofluid.

3. The implantable and bioresorbable device of claim 1 , wherein said array of dissolvable electrodes are a multiplexed array of dissolvable electrodes.

4. The implantable and bioresorbable device of claim 3 , further comprising an array of backplane transistors formed from said membrane of silicon in electrical contact with said array of dissolvable electrodes for high speed multiplexed addressing of said array of dissolvable electrodes.

5. The implantable and bioresorbable device of claim 4 , wherein said array of backplane transistors are MOSFETs.

6. The implantable and bioresorbable device of claim 5 , wherein said MOSFETs comprise a thin film of a metal, a gate dielectric and an interlayer dielectric.

7. The implantable and bioresorbable device of claim 6 , wherein:
said metal comprises Molybdenum (Mo) having a thickness less than 500 nm;
said gate dielectric comprises SiO 2 having a thickness less than 200 nm;
said interlayer dielectric comprises a multilayer stack of SiO 2 with a thickness less than 400 nm, Si 3 N 4 with a thickness less than 500 nm, and SiO 2 with a thickness less than 400 nm.

8. The implantable and bioresorbable device of claim 4 , further comprising for each electrode of the array of dissolvable electrodes:
a buffer transistor electrically connected to said electrode of the array of dissolvable electrodes for buffering of a measured tissue potential; and
a multiplexing transistor electrically connected to said electrode of the array of dissolvable electrodes for multiplexing of said array of dissolvable electrodes.

9. The implantable and bioresorbable device of claim 8 , further comprising a thin layer of metal electrically connected to said array of dissolvable electrodes to define column select lines.

10. The implantable and bioresorbable device of claim 4 , further comprising vertical interconnects to electrically connect said array of dissolvable electrodes to said array of backplane transistors, and said array of dissolvable electrodes are configured for physical contact with underlying tissue.

11. The implantable and bioresorbable device of claim 10 , wherein said vertical interconnects comprise vias.

12. The implantable and bioresorbable device of claim 4 , further comprising an encapsulation layer that covers said array of backplane transistors and said membrane of silicon.

13. The implantable and bioresorbable device of claim 12 , wherein said encapsulation layer comprises a bottom SiO 2 layer, a middle Si 3 N 4 layer and a top SiO 2 layer.

14. The implantable and bioresorbable device of claim 13 , wherein said encapsulation layer has a thickness less than or equal to 2 μm.

15. The implantable and bioresorbable device of claim 12 , further comprising a plurality of passages through said encapsulation layer and in spatial alignment with an active region of each of said electrodes of said array of dissolvable electrodes.

16. The implantable and bioresorbable device of claim 1 , wherein said membrane of silicon is patterned to form a plurality of parallel silicon ribbons, the device further comprising:
an encapsulation layer that covers a portion of said plurality of parallel silicon ribbons; and
a plurality of passages formed through said encapsulation layer, wherein the passages are aligned with said plurality of parallel silicon ribbons to form an array of exposed silicon electrically interconnected to regions of encapsulated silicon ribbons.

17. The implantable and bioresorbable device of claim 16 , further comprising a plurality MOSFETs formed from said membrane of silicon, wherein said membrane of silicon serves as both an active semiconductor material and a tissue interface electrode.

18. The implantable and bioresorbable device of claim 16 , further comprising an active region at a distal end of said plurality of parallel silicon ribbons connected to external electrical connectors separated from said distal end by a longitudinal distance that is greater than or equal to 3 mm.

19. The implantable and bioresorbable device of claim 1 , wherein the membrane of silicon thickness, a dopant concentration in the membrane of silicon, or both the membrane of silicon thickness and the dopant concentration in the membrane of silicon are selected to provide for accurate measurement of a biological parameter over a device lifetime.

20. The implantable and bioresorbable device of claim 19 , wherein the membrane of silicon thickness and/or the dopant concentration in the membrane of silicon is selected to provide a device lifetime that is greater than or equal to 10 days.

21. The implantable and bioresorbable device of claim 19 , wherein the membrane of silicon thickness and/or the dopant concentration in the membrane of silicon is selected to provide a device lifetime that is less than or equal to 2 days.

22. The implantable and bioresorbable device of claim 19 , wherein said membrane of silicon has a thickness that decreases as a function of implant duration, wherein said device maintains functionality for a decrease in thickness of up to 70%.

23. The implantable and bioresorbable device of claim 19 , wherein device lifetime is increased with increasing dopant concentration in the membrane of silicon and/or increasing said membrane of silicon thickness.

24. The implantable and bioresorbable device of claim 1 , wherein said membrane of silicon is doped with a high concentration of dopant.

25. The implantable and bioresorbable device of claim 24 , wherein said high concentration of dopant is greater than or equal to 10 18 cm −3 and less than or equal to 2×10 20 cm −3 .

26. The implantable and bioresorbable device of claim 24 , wherein said dopant is selected from the group consisting of phosphorus and boron.

27. The implantable and bioresorbable device of claim 1 , further comprising an insulation layer and electrical interconnects that electrically connect said electrodes of said array of dissolvable electrodes, wherein said insulation layer electrically isolates the electrical interconnects from biofluids and biological tissue during use.

28. The implantable and bioresorbable device of claim 27 , wherein the insulation layer comprises a layer of SiO 2 having a thickness less than or equal to 200 nm.

29. The implantable and bioresorbable device of claim 1 , wherein said membrane of silicon further comprises terminal pads configured to electrically interface with a biological tissue.

30. The implantable and bioresorbable device of claim 29 , wherein said terminal pads are exposed Si of said membrane of Si.

31. The implantable and bioresorbable device of cl

Assignees

• Univ Illinois

Inventors

• Rogers John A
• Yu Ki Jun

Classifications

• A61B5/293

  Invasive · CPC title

• A61B5/291

  for electroencephalography [EEG] · CPC title

• A61B5/302

  for capacitive or ionised electrodes, e.g. metal-oxide-semiconductor field-effect transistors [MOSFET] · CPC title

• A61L31/028

  Other inorganic materials not covered by A61L31/022 - A61L31/026 · CPC title

• A61L31/06

  obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds {(A61L31/041 takes precedence)} · CPC title