# US 9,437,628 B1 · Biodegradable microwave electronic devices

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- Number: US 9,437,628 B1
- Document ID: US9437628B1
- Status: Granted
- Kind: B1
- Application number: 14/709,850
- Filed: 2015-05-12
- Granted: 2016-09-06
- Earliest claimed: 2015-05-12
- Assignees: Wisconsin Alumni Research Foundation
- Applicants: Wisconsin Alumni Research Foundation
- Inventors: Zhenqiang Ma; Yei Hwan Jung; Shaoqin Gong; Tzu-Hsuan Chang
- Web page: https://patentgrep.com/patent/US9437628B1

## CPC

- H10D 86/80: characterised by multiple passive components, e.g. resistors, capacitors or inductors
- G01N 22/00: Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more (G01N3/00 - G01N17/00, G01N24/00 take precedence)
- H10D 86/01: Manufacture or treatment
- H10K 71/18: using non-liquid printing techniques, e.g. thermal transfer printing from a donor sheet
- H10K 77/111: {Flexible substrates}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

Substantially biodegradable microwave integrated circuits and method for making the microwave integrated circuits are provided. The integrated circuits, which have applications in high performance flexible microwave and digital electronics, utilize biobased, biodegradable cellulose nanofibril films as a substrate and comprise only very small amounts of potentially toxic inorganic materials.

## Claims

### Claim 1

A microwave integrated circuit comprising:
microwave integrated circuitry comprising active components and passive components, wherein at least one of the active components comprises a Group III-V semiconductor; and
a biodegradable, dielectric integrated circuit substrate in contact with one or more of the active and passive components;
wherein the integrated circuit substrate comprises an optically transparent film comprising cellulose nanofibrils and a hydrophobic polymer coating.

### Claim 2 (depends on 1)

The integrated circuit of claim 1, wherein the integrated circuit substrate has an RF loss tangent of no greater than 0.045 across the frequency range of 1 to 10 GHz.

### Claim 3 (depends on 2)

The integrated circuit of claim 2, wherein the integrated circuit substrate has a dielectric constant of no greater than 3 across the frequency range of 1 to 10 GHz.

### Claim 4 (depends on 1)

The integrated circuit of claim 1, comprising no greater than 25 wt. % of non-biodegradable materials.

### Claim 5 (depends on 1)

The integrated circuit of claim 1, wherein the active and passive components in the integrated circuit do not include any non-biodegradable dielectric substrates.

### Claim 6 (depends on 1)

The integrated circuit of claim 1, wherein the at least one active component comprises a bipolar transistor, a Schottky diode, or both; the Group III-V semiconductor is GaAs, GaInP or InP; and the active components do not include a semi-insulating GaAs substrate.

### Claim 7 (depends on 6)

The integrated circuit of claim 6, wherein the integrated circuit is a microwave rectifier circuit or a microwave amplifier circuit.

### Claim 8 (depends on 1)

The integrated circuit of claim 1, wherein the Group III-V semiconductor is GaAs and the hydrophobic polymer is an epoxy polymer.

### Claim 9 (depends on 1)

The integrated circuit of claim 1, wherein the active and passive components are encapsulated in a polymer that is substantially insoluble in water.

### Claim 10 (depends on 9)

The integrated circuit of claim 9, wherein the Group III-V semiconductor is GaAs, the hydrophobic polymer is an epoxy polymer and the polymer that is substantially insoluble in water is a polyimide.

### Claim 11 (depends on 1)

The integrated circuit of claim 1, wherein the integrated circuit substrate further comprises electrically insulating particles having a thermal conductivity of at least 30 W/m K.

### Claim 12

A method of making a microwave integrated circuit, the method comprising:
forming passive and active components for a microwave integrated circuit on one or more non-biodegradable substrates, wherein at least one of the active components comprises a Group III-V semiconductor;
releasing the passive and active components from the one or more non-biodegradable substrates; and
transferring the passive and active components onto a biodegradable, dielectric integrated circuit substrate, such that the passive and active components form the integrated circuitry of the microwave integrated circuit;
wherein the biodegradable, dielectric integrated circuit substrate comprises an optically transparent film comprising cellulose nanofibrils and a hydrophobic polymer coating.

### Claim 13 (depends on 12)

The method of claim 12, wherein the integrated circuit substrate has an RF loss tangent of no greater than 0.045 across the frequency range of 1 to 10 GHz.

### Claim 14 (depends on 13)

The method of claim 13, wherein the integrated circuit substrate has a dielectric constant of no greater than 3 across the frequency range of 1 to 10 GHz.

### Claim 15 (depends on 12)

The method of claim 12, wherein the integrated circuit comprises no greater than 25 wt. % of non-biodegradable materials.

### Claim 16 (depends on 12)

The method of claim 12, further comprising encapsulating the active and passive components in a polymer that is substantially insoluble in water.

### Claim 17 (depends on 12)

The method of claim 12, wherein the Group III-V semiconductor is GaAs and the hydrophobic polymer is an epoxy polymer.