# US 11,077,664 B2 · Systems and methods for controlling the morphology and porosity of printed reactive inks for high precision printing

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- Number: US 11,077,664 B2
- Document ID: US11077664B2
- Status: Granted
- Kind: B2
- Application number: 16/614,341
- Filed: 2018-05-17
- Published: 2020-05-14
- Granted: 2021-08-03
- Earliest claimed: 2017-05-17
- Assignees: Arizona Board of Regents on behalf of Arizona State University
- Applicants: Mariana Bertoni; April Jeffries; Owen Hildreth; Avinash Mamidanna
- Inventors: Mariana Bertoni; April Jeffries; Owen Hildreth; Avinash Mamidanna
- Web page: https://patentgrep.com/patent/US11077664B2

## CPC

- B41J 2/1607: {Production of print heads with piezoelectric elements (B41J2/1606, B41J2/162 take precedence)}
- C08K 3/08: Metals
- C09D 11/36: based on non-aqueous solvents
- C09D 11/38: characterised by non-macromolecular additives other than solvents, pigments or dyes
- C09D 11/52: Electrically conductive inks
- B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)

## Abstract

Systems and methods for optimizing morphology and electrical properties of silver printed on a substrate with a particular implementation in photovoltaic manufacturing techniques. The system comprises a substrate, a printer jet head having a nozzle to dispense a reactive metal ink and a solvent onto the substrate, and wherein the solvent and a temperature of the substrate are controlled during deposition of the reactive metal ink onto the substrate to produce a dense film in the absence of sintering.

## Claims

### Claim 1

A system for printing metal on a substrate, the system comprising:
a temperature-controlled stage configured to hold the substrate and to maintain a temperature of the substrate at a target temperature, wherein the target temperature is greater than room temperature; and
a printer jet head having a nozzle to dispense a reactive metal ink and a solvent onto the substrate,
wherein the temperature-controlled stage is configured to control the temperature of the substrate during deposition of the reactive metal ink onto the substrate to produce a dense film in the absence of sintering.

### Claim 2 (depends on 1)

The system of claim 1, wherein the reactive metal ink is a self-reducing silver-diamine ink.

### Claim 3 (depends on 2)

The system of claim 2, wherein the solvent comprises ethanol or 2,3-butanediol.

### Claim 4 (depends on 3)

The system of claim 3, wherein the temperature of the substrate is controlled to a range of between about 60° C. and about 80° C.

### Claim 5 (depends on 4)

The system of claim 4, wherein electrical resistivity of the dense film is about 1 μΩcm to about 2 μΩcm.

### Claim 6 (depends on 4)

The system of claim 4, wherein electrical resistivity of the dense film is about 1.8 μΩcm.

### Claim 7 (depends on 4)

The system of claim 4, wherein porosity of the dense film is about 45% to about 55%.

### Claim 8 (depends on 4)

The system of claim 4, wherein porosity of the dense film is about 50%.

### Claim 9 (depends on 3)

The system of claim 3, wherein the temperature of the substrate is controlled to about 66° C.

### Claim 10 (depends on 1)

The system of claim 1, wherein porosity of the dense film is reduced by at least 40% when the solvent comprises ethanol.

### Claim 11 (depends on 1)

The system of claim 1, wherein media resistivity of the dense film is reduced by two orders of magnitude when the solvent is ethanol and the temperature of the substrate is 66° C.

### Claim 12 (depends on 11)

The system of claim 11, wherein concentration of the reactive metal ink to the ethanol is 10 to 1.

### Claim 13 (depends on 1)

The system of claim 1, wherein the nozzle includes an orifice having a diameter of equal to or less than 60 μm and a diamond-like coating to reduce wetting.

### Claim 14 (depends on 1)

The system of claim 1, further comprising a camera positioned with a field of view including a surface of the temperature-controlled stage where the substrate is held during the deposition of the reactive metal ink onto the substrate, wherein the system is configured to adjust printing parameters by monitoring formation of droplets including the reactive metal ink and the solvent dispensed from the nozzle onto the substrate based on image data captured by the camera.

### Claim 15 (depends on 14)

The system of claim 14, wherein the system is configured to adjust printing parameters by adjusting at least one selected from a group consisting of a solvent-to-ink ratio of the droplets dispensed by the nozzle and a temperature of the substrate.

### Claim 16 (depends on 1)

The system of claim 1, further comprising:
a camera positioned with a field of view including a surface of the temperature-controlled stage where the substrate is held during the deposition of the reactive metal ink onto the substrate; and
a controller configured to
determine, based on image data from the camera, a contact angle of a droplet formed on the substrate, the droplet including the reactive metal ink and the solvent dispensed by the nozzle; and
adjust a solvent-to-ink ratio of droplets dispensed by the nozzle based on a comparison of the determined contact angle and a target contact angle.

### Claim 17

A system of optimizing morphology and electrical properties of a reactive metal ink printed on a substrate, the system comprising:
a printer jet head having a nozzle to dispense droplets comprising a reactive metal ink and a solvent onto the substrate to produce a dense film in the absence of sintering;
a temperature-controlled stage configured to hold the substrate during dispensing of the droplets onto the substrate and to control a temperature of the substrate, wherein the temperature-controlled stage is configured to maintain the temperature of the substrate at a temperature between about 60° C. and about 80° C. during deposition of the reactive metal ink onto the substrate,
wherein a contact angle of a dispensed droplet relative to the substrate is less than 15°,
wherein a concentration of the solvent to reactive metal ink ranges between 1:1 and 10:1,
such that the dense film provides media resistivity less than 2 μΩcm with an optimized morphology with a porosity less than 60%.

### Claim 18 (depends on 17)

The system of claim 17, wherein the solvent is ethanol or 2,3-butanediol, and wherein the reactive metal ink includes silver.

### Claim 19 (depends on 17)

The system of claim 17, wherein the nozzle includes an orifice having a diameter of equal to or less than 60 μm and a diamond-like coating to reduce wetting.

### Claim 20 (depends on 17)

The system of claim 17, wherein the reactive metal ink is silver.

### Claim 21 (depends on 17)

The system of claim 17, further comprising:
a camera positioned with a field of view including a surface of the temperature-controlled stage where the substrate is held during the deposition of the droplets onto the substrate; and
a controller configured to
determine the contact angle of at least one dispensed droplet on the substrate based on image data from the camera; and
adjust a solvent-to-ink ratio of the droplets dispensed by the nozzle when the determined contact angle is greater than 15°.