# US 2024/0201585 A1 · Photoresist formulations 3d microprinting techniques

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- Number: US 2024/0201585 A1
- Document ID: US20240201585A1
- Status: Published application
- Kind: A1
- Application number: 18/562,549
- Filed: 2022-05-20
- Published: 2024-06-20
- Earliest claimed: 2021-05-24
- Assignees: Fondazione Istituto Italiano Di Tecnologia
- Applicants: Fondazione Istituto Italiano Di Tecnologia
- Inventors: Marco Carlotti; Omar Tricinci; Virgilio Mattoli
- Web page: https://patentgrep.com/patent/US20240201585A1

## CPC

- G03F 7/0037: {Production of three-dimensional images}
- B33Y 10/00: Processes of additive manufacturing
- B33Y 70/00: Materials specially adapted for additive manufacturing
- B33Y 80/00: Products made by additive manufacturing
- G03F 7/027: Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds (G03F7/075 takes precedence)
- G03F 7/031: Organic compounds not covered by group G03F7/029
- G03F 7/2053: {using a laser (ablative removal B41C)}
- G03F 7/70025: {by lasers}
- G03F 7/70375: {Multiphoton lithography or multiphoton photopolymerization; Imaging systems comprising means for converting one type of radiation into another type of radiation}
- G03F 7/029: Inorganic compounds; Onium compounds; Organic compounds having hetero atoms other than oxygen, nitrogen or sulfur
- G03F 7/325: {Non-aqueous compositions}
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- B33Y: ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING

## Abstract

The present invention fits into the 3D microprinting sector and relates to a process for producing degradable 3D polymeric nano- or microstructures having sub-micrometre resolution. The process of the invention uses a photoresist formulation comprising a mixture of: (i) cyclic ketene acetal monomers; (ii) vinyl and/or (meth)acrylic monomers; and (iii) at least one photoinitiator. The process of the invention is based on two-photon polymerisation photoinitiated by focusing a laser beam within said photoresist formulation, with the obtainment of polymeric nano- or microstructures degradable under mild conditions and having sub-micrometre resolution.

## Claims

### Claim 1

3D micro-printing process via two-photon polymerisation for producing degradable 3D polymeric nano- or microstructures having sub-micrometre resolution, said process comprising the steps of:
(a) providing a photoresist formulation comprising:
(i) Cyclic ketene acetal monomers of general formula (I):
selected from the group consisting of:
2-methylene-1,3-dioxane, 4-methyl-2-methylene-1,3-dioxane, 4,4,5,5-tetramethyl-2-methylene-1,3-dioxane, 2,4-dimethylene-1,3-dioxane, 2-methylene-hexhydrobenzo[d][1,3]dioxole, 2-methylene-1,3-dioxane, 4,6-dimethyl-2-methylene-1,3-dioxane, 5,5-dimethyl-2-methylene-1,3-dioxane, 2-methylene-4-phenyl-1,3-dioxane, 2-methylene-5,5-diphenyl-1,3-dioxane, 2-methylene-1,3-dioxepane (MDO), 4,7-dimethyl-2-methylene-1,3-dioxepane, 3-methylene-1,5-dihydrobenzo[e][1,3]dioxepine, 4-methylene-3,5-dioxabicyclo[5.1.0]octane, 2-(difluoromethylene)-1,3-dioxepane, 5,6-dimethoxy-2-methylene-1,3-dioxepane, 2-methylene-1,3-dithiepane, 3,9-dimethylene-1,5,8,10-tetraoxaspiro[5.5]undecane, and a combination thereof;
(ii) vinyl and/or (meth)acrylic monomers selected from the group consisting of: pentaerythritol tetraacrylate, pentaerythritol triacrylate, 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, bisphenol A diacrylate, tricyclo[5.2.1.02,6]decanedimethanol diacrylate, trimethylolpropane triacrylate, ethyl acrylate, ethylene-methyl acrylate, methyl methacrylate, 2-chloroethyl vinyl ether, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, butyl acrylate, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, chloroprene, styrene, and a combination thereof;
(iii) at least one photoinitiator;
(b) focusing a laser beam within said photoresist formulation by directing said laser beam until localised polymerisation of said photoresist into a 3D cross-linked polymeric nano- or microstructure is achieved;
(c) removing the non-cross-linked portion of photoresist by washing with a solvent.

### Claim 2 (depends on 1)

Process according to claim 1, wherein said process is a subtractive manufacturing process.

### Claim 3 (depends on 1)

Process according to claim 1, wherein said at least one photoinitiator (iii) is selected from the group consisting of: 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 2-Benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone, 2-Methyl-4′-(methylthio)-2-morpholinopropiophenone, 1-Hydroxy-cyclohexyl-phenylketone, 2-Hydroxy-2-methylpropiophenone, 2,2-Dimethoxy-2-phenylacetophenone, lithium phenyl-2,4,6-trimethylbenzoylphospinate, and a combination thereof.

### Claim 4 (depends on 1)

Process according to claim 1, wherein said solvent of step (c) is selected from the group consisting of: isopropyl alcohol, chloroform, dichloromethane, hexane, propylene glycol methyl ether acetate and a combination thereof.

### Claim 5 (depends on 1)

Process according to claim 1, wherein said photoresist formulation further comprises:
(iv) at least one solvent which does not interact with the other components (i)-(iii) of the formulation, this solvent being selected from the group consisting of: cyrene, dimethylformamide, dimethylsulfoxide, pentadecane, hexadecane, heptadecane, octadecane, and a combination thereof.

### Claim 6 (depends on 1)

Process according to claim 1, wherein said photoresist formulation comprises said cyclic ketene acetal monomers (i) in a concentration of between 20 and 90 wt % relative to the total weight of the formulation.

### Claim 7 (depends on 1)

Process according to claim 1, wherein said photoresist formulation comprises said vinyl and/or (meth)acrylic monomers (ii) in a concentration of from 5 to 50 wt % relative to the total weight of the formulation.

### Claim 8 (depends on 1)

Process according to claim 1, wherein said photoresist formulation comprises said at least one photoinitiator (iii) in a concentration of between 1 and 15 wt % relative to the total weight of the formulation.

### Claim 9 (depends on 5)

Process according to claim 5, wherein said photoresist formulation comprises said at least one solvent (iv) in a concentration of between 1 and 30% by weight relative to the total weight of the formulation.

### Claim 10 (depends on 1)

3D polymeric nano- or microstructure obtainable by the process according to claim 1, said nano- or microstructure having sub-micrometre resolution and being characterised by being completely degradable under at least one of the following conditions:
within 3 hours at a temperature between 35 and 80° C., in 0.25-5 M KOH solutions in methanol;
within 3 hours at a temperature between 50 and 100° C., in basic aqueous solutions with a pH≥12, or
within 9 hours at a temperature between 50 and 100° C. in sulphuric acid solutions with a pH≤1.

### Claim 11

Photoresist formulation comprising:
(i) cyclic ketene acetal monomers of general formula (I):
selected from the group consisting of:
2-methylene-1,3-dioxane, 4-methyl-2-methylene-1,3-dioxane, 4,4,5,5-tetramethyl-2-methylene-1,3-dioxane, 2,4-dimethylene-1,3-dioxane, 2-methylene-hexhydrobenzo[d][1,3]dioxole, 2-methylene-1,3-dioxane, 4,6-dimethyl-2-methylene-1,3-dioxane, 5,5-dimethyl-2-methylene-1,3-dioxane, 2-methylene-4-phenyl-1,3-dioxane, 2-methylene-5,5-diphenyl-1,3-dioxane, 2-methylene-1,3-dioxepane (MDO), 4,7-dimethyl-2-methylene-1,3-dioxepane, 3-methylene-1,5-dihydrobenzo[e][1,3]dioxepine, 4-methylene-3,5-dioxabicyclo[5.1.0]octane, 2-(difluoromethylene)-1,3-dioxepane, 5,6-dimethoxy-2-methylene-1,3-dioxepane, 2-methylene-1,3-dithiepane, 3,9-dimethylene-1,5,8,10-tetraoxaspiro[5.5]undecane, and a combination thereof;
(ii) vinyl and/or (meth)acrylic monomers selected from the group consisting of: pentaerythritol tetraacrylate, pentaerythritol triacrylate, 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, bisphenol A diacrylate, tricyclo[5.2.1.02,6]decanedimethanol diacrylate, trimethylolpropane triacrylate, ethyl acrylate, ethylene-methyl acrylate, methyl methacrylate, 2-chloroethyl vinyl ether, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, butyl acrylate, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, chloroprene, styrene, and a combination thereof;
(iii) at least one photoinitiator;

### Claim 12 (depends on 11)

Photoresist formulation according to claim 11, wherein said at least one photoinitiator (iii) is selected from the group consisting of: 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 2-Benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone, 2-Methyl-4′-(methylthio)-2-morpholinopropiophenone, 1-Hydroxy-cyclohexyl-phenylketone, 2-Hydroxy-2-methylpropiophenone, 2,2-Dimethoxy-2-phenylacetophenone, lithium phenyl-2,4,6-trimethylbenzoylphospinate, and a combination thereof.

### Claim 13 (depends on 11)

Photoresist formulation according to claim 11, further comprising:
(iv) at least one solvent which does not interact with the other components (i)-(iii) of the formulation, this solvent being selected from the group consisting of: cyrene, dimethylformamide, dimethylsulfoxide, pentadecane, hexadecane, heptadecane, octadecane, and a combination thereof.

### Claim 14 (depends on 11)

Photoresist formulation according to claim 11, comprising said cyclic ketene acetal monomers (i) in a concentration of between 20 and 90 wt % relative to the total weight of the formulation.

### Claim 15 (depends on 11)

Photoresist formulation according to claim 11, comprising said vinyl and/or (meth)acrylic monomers (ii) in a concentration of between 5 to 50 wt % relative to the total weight of the formulation.

### Claim 16 (depends on 11)

Photoresist formulation according to claim 11, comprising said at least one photoinitiator (iii) in a concentration of between 1 and 15 wt % relative to the total weight of the formulation.

### Claim 17 (depends on 13)

Photoresist formulation according to claim 13, comprising said at least one solvent (iv) in a concentration of between 1 and 30% by weight relative to the total weight of the formulation.

### Claim at position 18

-19. (canceled)

### Claim 20 (depends on 2)

The process according to claim 2, wherein said process is a direct laser writing process or 3D micro-lithography.

### Claim 21 (depends on 8)

The process according to claim 8, wherein said photoresist formulation comprises said at least one photoinitiator (iii) in a concentration of 3 to 5 wt % relative to the total weight of the formulation.

### Claim 22 (depends on 9)

Process according to claim 9, wherein said photoresist formulation comprises said at least one solvent (iv) in a concentration of between 4 and 25% by weight relative to the total weight of the formulation.