3D printing ink and printing method for flexible organic electrochemical transistor

Abstract

The present invention discloses a 3D printing ink and a printing method for a flexible organic electrochemical transistor, belonging to the technical field of organic electrochemical transistors. The substrate ink is a crosslinker obtained by mixing nanofiber cellulose NFC / polyvinyl alcohol (PVA) hydrogel with glutaraldehyde and then subjecting it to acid treatment. The electrode ink is a reduced graphene oxide (rGO) / CNT electrode prepared from graphene oxide / carbon nanotubes (CNT). The active layer ink includes a channel active layer ink and a gate active layer ink. Both the channel active layer ink and the gate active layer ink include PEDOT:PSS material. The insulating layer ink includes PDMS. The dielectric layer ink includes PSSNa gel electrolyte ink. The ink printing parameters are set and printing is performed using a 3D printing system. The present invention realizes the printing of organic electrochemical transistors with a size of less than 20 μm through an extrusion 3D printing process, thereby realizing full 3D printing of flexible organic electrochemical transistor devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible organic electrochemical transistors, and specifically relates to a 3D printing ink and a printing method for a flexible organic electrochemical transistor. Background Art

[0002] Flexible organic electrochemical transistors are one of the most basic devices in flexible electronics. Unlike traditional semiconductor devices, flexible transistors are built on substrates such as paper, plastic or metal foil and are composed of organic active thin-film semiconductor materials. Compared with crystalline silicon, they have the advantages of being thinner, more flexible and having lower manufacturing costs. The doping changes in flexible organic electrochemical transistors occur across the entire channel, resulting in high transconductance. Flexible organic electrochemical transistors can control large drain currents at low gate voltages, making them efficient switches and high-performance amplifiers. In addition, good biocompatibility makes it possible to biofunctionalize organic electrochemical transistors. Flexible organic electrochemical transistors are used in rollable displays, flexible smart cards, consistent sensors and artificial skin due to their bendability, light weight, low power consumption, ease of integration, high sensitivity and large-area solution manufacturing.

[0003] Traditional methods for fabricating organic electrochemical transistors include screen printing, inkjet printing, aerosol jet printing, and photolithography. Photolithography is the most common method for fabricating organic electrochemical transistors and their circuits, offering excellent yield, high resolution, and scalability. However, traditional fabrication methods struggle to meet the design requirements for rapidly realizing novel material concepts and devices, as well as for application in complex environments. In this regard, 3D printing offers distinct advantages over conventional printing. Compared to screen printing, gravure printing, or inkjet printing, 3D printing offers superior flexibility in material selection, ink preparation, and pattern design / modification. 3D printing offers a wide viscosity range, allowing for the deposition of materials ranging from insulators to semiconductors and conductors. Because new screens do not need to be produced for any pattern changes, 3D printing offers greater flexibility in pattern modification than screen printing. Compared to inkjet printing, 3D printing can achieve finer resolution when patterning highly viscous materials, enabling applications such as the integration of organic electrochemical transistors with traditional microfluidics.

[0004] However, there are still difficulties in developing suitable metal and semiconductor inks and creating alternatives to liquid electrolytes. Currently, 3D printing can only print semiconductor layers and dielectric layers in the application of organic electrochemical transistors, and it is impossible to prepare the entire organic electrochemical transistor through 3D printing. Summary of the Invention

[0005] The present invention overcomes the shortcomings of the existing technology and proposes a 3D printing ink and printing method for a flexible organic electrochemical transistor; different printing inks are used for each functional area of ​​the flexible organic electrochemical transistor, and the entire organic electrochemical transistor is prepared by 3D printing.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions.

[0007] A 3D printing ink for a flexible organic electrochemical transistor, comprising a base ink, an electrode ink, an active layer ink, an insulating layer ink, and a dielectric layer ink;

[0008] The base ink is a crosslinker obtained by mixing nanofiber cellulose NFC / polyvinyl alcohol PVA hydrogel with glutaraldehyde and then treating it with acid;

[0009] The electrode ink is a reduced graphene oxide rGO / CNT electrode prepared from graphene oxide / carbon nanotubes CNT;

[0010] The active layer ink includes a channel active layer ink and a gate active layer ink; the channel active layer ink and the gate active layer ink both include PEDOT:PSS material;

[0011] The insulating layer ink includes PDMS;

[0012] The dielectric layer ink includes PSSNa gel electrolyte ink.

[0013] Preferably, the graphene oxide / carbon nanotube (CNT) is treated with potassium iodide in hydrochloric acid to produce the reduced graphene oxide (rGO / CNT) electrode portion. Specifically, the base ink comprises a nanofiber cellulose (NFC) / polyvinyl alcohol (PVA) (1:1 ratio) hydrogel that can be processed at relatively low temperatures (<100°C). To render it insoluble in water, it is mixed with glutaraldehyde and then treated with acid to produce the base ink. The NFC / PVA base plane is 3D printed and oven-dried to produce a 50-70 μm thick film that serves as the flexible substrate.

[0014] Specifically, the electrode ink was prepared using a mixed dispersion of graphene oxide (GO) and carbon nanotubes (CNTs). GO / CNT source, drain, and gate electrodes were 3D printed on a substrate film. The source and drain electrodes were set to have a width of 1-2 mm and an equivalent length of 5-10 mm. The gate electrode had the same width as the source and drain electrodes, with an equivalent length of 3.3-8.3 mm. The NFC / PVA film and GO / CNT electrodes were immersed in a reducing solution for reduction treatment, generating the reduced graphene oxide (rGO / CNT) electrode portion. Iodine contamination in the rGO / CNT electrodes was removed by immersing the substrate and electrodes in ethanol and then drying.

[0015] Preferably, the channel active layer ink also includes an excess of d-sorbitol. Specifically, the channel active layer and gate active layer inks primarily utilize a relatively low concentration of PEDOT:PSS material, to which an excess of d-sorbitol is added to maintain mobile ions within the semiconductor polymer and promote adhesion to the substrate. To improve the water stability of the PEDOT:PSS channel without sacrificing conductivity, divinyl sulfone (DVS) is added to the dielectric layer ink. An active channel with an aspect ratio of 1 / 3 to 1 / 3.2 and a length L ranging from 75 to 85 μm is 3D printed between the source and drain electrodes.

[0016] Preferably, the insulating layer ink is made from two different batches of PDMS: Sylgard 184 and SE 1700 are mixed and centrifuged to disperse uniformly, and then isopropyl alcohol is added to the mixture as a diluent and centrifuged again to obtain a uniform insulating layer ink. Specifically, Sylgard 184 (Sy 184) and SE 1700 (Dow Corning, Auburn, MI) are mixed with their respective curing agents in a ratio of 10:1. The mixture of the two is mixed and centrifuged in a ratio of 6:4, and then isopropyl alcohol (IPA) is added in a ratio of 1:2 to dilute and centrifuge to obtain the insulating layer ink.

[0017] Preferably, the dielectric layer ink is prepared by dispersing PSSNa and d-sorbitol in aluminum chloride and glycerol, followed by magnetic stirring on a high-temperature hot plate, and finally stirring at room temperature to remove gel bubbles.

[0018] A 3D printing method for preparing a flexible organic electrochemical transistor using the above-mentioned 3D printing ink comprises preparing the substrate ink, electrode ink, active layer ink, insulating layer ink, and dielectric layer ink; drawing the size of the organic electrochemical transistor, then setting the ink printing parameters, and printing using a 3D printing system.

[0019] Preferably, the parameters of the base ink are set as follows: nozzle 27 G, pressure 70 Pa, and speed 25 mm / s.

[0020] Preferably, the parameters of the electrode ink are set as follows: nozzle 30 G, pressure 70 Pa, speed 10 mm / s, and resolution between 120 and 150 μm.

[0021] Preferably, the PEDOT:PSS channel active layer ink parameter settings are: nozzle 34 G; pressure 80 Pa; speed 5 mm / s; resolution 100 ~ 120 μm; gate active layer ink parameter settings are: nozzle 30 G; pressure 200 Pa; speed 15 mm / s; resolution 150 μm.

[0022] Preferably, the insulating layer ink parameter settings are: nozzle 30 G; pressure 200 Pa; speed 15 mm / s; resolution 150 μm; dielectric layer ink parameter settings are: nozzle 32 G; pressure 500 Pa; speed 10 mm / s; resolution 120 μm.

[0023] After the active layer printing step, a "U"-shaped PDMS cavity film is printed on the device as an insulating layer. A 1 mm distance is reserved below the device as the external interface of the three electrodes. The area of ​​the printed opening above the source, drain, gate and channel is 2.2 to 4.5 mm. 2 Reserved for dielectric layer.

[0024] The beneficial effects of the present invention compared to the prior art are:

[0025] The present invention designs specific inks and parameters for each part of the organic electrochemical transistor, and realizes the printing of organic electrochemical transistors with a size of less than 20 μm through an extrusion 3D printing process, realizing the full 3D printing of flexible organic electrochemical transistor devices. This is far superior to the 50 μm size of organic electrochemical transistor devices prepared by existing 3D printing technology, and can realize organic electrochemical transistor devices with smaller size, lower power consumption and better performance. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. The technical solutions of the present invention will be described in detail below with reference to the embodiments, but the scope of protection is not limited thereto.

[0027] The fully printed flexible organic electrochemical transistor consists of a substrate, an electrode plane above the substrate, an active channel between the source and drain electrodes and on the gate, an insulating layer above the electrode, and a dielectric layer in a hole reserved in the center of the insulating layer. The dielectric layer covers the gap in the insulating layer, directly above the electrode and channel, and connects the channel and electrode. The overall size of the fully printed flexible organic electrochemical transistor device is limited to 25 to 100 mm. 2 Inside.

[0028] The above-mentioned organic electrochemical transistor can be completely prepared using a single printer. The 3D printing method for the above-mentioned organic electrochemical transistor: The present invention uses a commercial extrusion 3D printing system (Cellink BIOX) to prepare the organic electrochemical transistor. The dimensions of the organic electrochemical transistor are drawn using Blender software and saved as .stl files. These files are then sliced ​​using the built-in BIOX software. The printing parameters for each material are reported below:

[0029] Step 1: Preparation of a flexible organic electrochemical transistor flexible substrate, including preparation of cellulose ink and 3D printing of the substrate layer.

[0030] Preparation of cellulose ink: 51.35 g of carboxymethyl nanofiber cellulose (1 wt% solid content, Research Institute of Sweden (RISE)), 11 g of 2 mg / mL-polyvinyl alcohol (PVA, Mowiol 18-88, Sigma-Aldrich) solution and 44 mg of 25 wt% glutaraldehyde solution (Sigma-Aldrich) were homogenized using a laboratory mixer (T 10 basic ULTRA-TURRAX@, IKA) for 10 min and then degassed in a vacuum desiccator overnight to remove excess bubbles in the viscous mixture.

[0031] Substrate cellulose ink parameter settings: nozzle: 27 G; pressure: 70 Pa; speed: 25 mm / s; resolution: 200 μm.

[0032] Step 2: Preparation of a flexible organic electrochemical transistor electrode, including the synthesis of graphene oxide, preparation of graphene oxide / carbon nanotube ink, and 3D printing of the electrode.

[0033] 2.1 Graphene Oxide Synthesis: All chemicals, including graphite flakes (-325 mesh), sulfuric acid (H2SO4, 98%), potassium permanganate (KMnO4), hydrochloric acid (HCl), and hydrogen peroxide (H2O2), were obtained from Sigma-Aldrich and used as received. In a 250 mL flask, 3 g of graphite flakes were dispersed in 90 mL of 98% H2SO4 and stirred at room temperature for 30 min. Then, 9 g of KMnO4 was slowly added to the flask under vigorous stirring. The oxidation process was carried out at room temperature for 3 h. The reaction was then poured into 500 mL of deionized water containing 10 mL of H2O2 to reduce the Mn. The suspension was stirred for 10 min and allowed to stand overnight. The supernatant was then decanted and washed three times with a 10 vol% HCI solution by centrifugation (10,000 rpm, 5 min) to remove sulfate ions. The samples were washed three times with deionized water and then centrifuged (10,000 rpm, 50 min) to remove the acid residue.

[0034] 2.2 Preparation of graphene oxide / carbon nanotube ink: 150 mg of graphene oxide and 75 mg of carbon nanotubes (-50 μm purchased from Jiangsu Xinfu Nanomaterial Technology Co., Ltd.) were dispersed in 10 ml of 50 vol% dimethyl sulfoxide (DMSO) / HO and sonicated for 6 h to prepare graphene oxide / carbon nanotube ink.

[0035] 2.3 GO / CNT ink parameter setting.

[0036] Nozzle: 30 G, Pressure: 70 Pa, Speed: 10 mm / s. Resolution is between 120 and 150 μm.

[0037] GO / CNT source, drain, and gate electrodes were 3D-printed on a substrate film. The source and drain electrodes were designed to have a width of 1-2 mm and an equivalent length of 5-10 mm. The gate electrode had the same width as the source and drain electrodes, with an equivalent length of 3.3-8.3 mm. The NFC / PVA film and GO / CNT electrodes were immersed in a reducing solution for reduction, generating the reduced graphene oxide (rGO / CNT) electrode portion. Iodine contamination in the rGO / CNT electrodes was removed by immersing the substrate and electrodes in ethanol and then drying.

[0038] Step 3: Preparation of an active layer of a flexible organic electrochemical transistor, including preparation of a conductive PEDOT:PSS ink and 3D printing of the active layer.

[0039] 3.1 Preparation of Conductive PEDOT:PSS Ink: 100 ml of PEDOT:PSS (PH1000, Heraeus) was frozen in liquid nitrogen and placed in a freeze-drying system (BenchTop Pro, SP-Scientific) for 72 h to eliminate all solvent. The dried PEDOT:PSS was then redispersed in DMSO / H₂O (5 / 95 vol%) at a 4 wt% ratio. To improve the plasticity of the formulation, 1 wt% DSorbitol and 4 wt% Triton X were added. The mixture was first stirred for 5 min using a homogenizer (T 10 basic ULTRA-TURRAX@, IKA), followed by magnetic stirring on a hot plate at 120 °C. (3-Trimannuroyloxypropyl)trimethoxysilane (GOPS, 0.1 wt%) was then added, and the solution was placed in a vacuum chamber for 30 min to remove all bubbles.

[0040] 3.2 Preparation of PEDOT:PSS Ink for OECT Channels: 100 ml of a commercial PEDOT:PSS formulation (PH1000, Heraeus) was frozen in liquid nitrogen and then inserted into our freeze-drying system (BenchTop Pro, SP-Scientific) for 72 h to eliminate all solvent. The dried PEDOT:PSS was then redispersed in DMSO / H₂O at a 2.5% ratio (5 / 95 vol%). To increase the plasticity of the formulation, 2 wt% Triton X was subsequently added. Furthermore, 20 wt% d-sorbitol was added to increase plasticity and facilitate ion diffusion within the PEDOT:PSS membrane. The solution was first stirred for 5 min using a homogenizer (T 10 basicULTRA-TURRAX@, IKA) and then magnetically stirred on a hot plate at 120 °C overnight. Glycerol (1 wt%) and divinyl sulfone (DVS, 3 vol%) were then added to the solution to crosslink the PSS at room temperature without losing conductivity. Finally, the solution was placed in a vacuum chamber for 30 min to remove all air bubbles.

[0041] 3.3 PEDOT:PSS channel ink parameter settings. Nozzle: 34 G. Pressure: 80 Pa. Speed: 5 mm / s. Resolution between 100 and 120 μm.

[0042] PEDOT:PSS gate ink parameter settings. Nozzle: 30 G. Pressure: 200 Pa. Speed: 15 mm / s. Resolution: 150 μm.

[0043] An active channel with an aspect ratio of 1 / 3 to 1 / 3.2 and a length L ranging from 75 to 85 μm is 3D printed between the source and drain.

[0044] Step 4: Preparation of a flexible organic electrochemical transistor insulating layer, including preparation of PDMS ink and 3D printing of the insulating layer.

[0045] PDMS ink preparation: Two different PDMS formulations, 10 g each of Sylgard 184 (Sy 184) and SE 1700 (DowCorning, Auburn, MI), were prepared by mixing them with their respective curing agents in a 10:1 ratio. Each mixture was then mixed separately to ensure proper dispersion of the curing agents (ARE-250 CE, Thinkymixer). Sy 184 and SE 1700 were then mixed in a 6:4 ratio and centrifuged to ensure uniform dispersion. Isopropyl alcohol (IPA) was then added as a diluent in a 1:2 ratio; the final formulation was centrifuged again to obtain a homogeneous 3D ink.

[0046] Insulating layer PDMS ink parameter settings: Nozzle: 30 G. Pressure: 200 Pa. Speed: 15 mm / s. Resolution: 150 μm.

[0047] After the active layer printing step, a "U"-shaped PDMS cavity film is printed on the device as an insulating layer. A 1 mm distance is reserved below the device as the external interface of the three electrodes. The area of ​​the printed opening above the source, drain, gate and channel is 2.2 to 4.5 mm. 2 Reserved for dielectric layer.

[0048] Step 5: Preparation of a flexible organic electrochemical transistor dielectric layer, including preparation of PSSNa gel electrolyte ink and 3D printing of the dielectric layer.

[0049] PSSNa gel electrolyte ink preparation: 2.5 g of PSSNa (Sigma, Mw 2,000,000) and 0.5 g of d-sorbitol were dispersed in 5 ml of 0.2 M aluminum chloride (AICls) and 10 ml of glycerol. These ingredients were magnetically stirred on a 150°C hotplate and then stirred at room temperature for one day to remove any bubbles from the gel. The dielectric layer was then 3D printed to fill the gap between the insulating layers.

[0050] Dielectric layer PSSNa electrolyte ink parameter settings. Nozzle: 32 G. Pressure: 500 Pa. Speed: 10 mm / s. Resolution: 120 μm.

[0051] These parameters are derived from an optimization process to ensure good filament extrusion and pattern filling with optimal resolution. Higher pressure values ​​lead to over-deposition of material (thus, lower resolution), while lower pressures result in incomplete filling of the pattern due to non-optimal filament extrusion. Regarding print speed, higher values ​​lead to suboptimal fiber deposition, producing incomplete patterns, while lower values ​​contribute to material spreading, which reduces resolution.

[0052] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be considered that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the present invention, which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.

Claims

1. A 3D printing ink for flexible organic electrochemical transistors, characterized in that: Including base ink, electrode ink, active layer ink, insulating layer ink and dielectric layer ink; The base ink is a crosslinker obtained by mixing nanofiber cellulose NFC / polyvinyl alcohol PVA hydrogel with glutaraldehyde and then treating it with acid; The electrode ink is prepared by treating graphene oxide / carbon nanotubes (CNT) with potassium iodide in hydrochloric acid to generate a reduced graphene oxide rGO / CNT electrode; The active layer ink includes a channel active layer ink and a gate active layer ink; the channel active layer ink and the gate active layer ink both include PEDOT:PSS material; the channel active layer ink also includes an excess of d-sorbitol; The insulating layer ink includes PDMS; The dielectric layer ink comprises PSSNa gel electrolyte ink; divinyl sulfone is added to the dielectric layer ink.

2. The 3D printing ink for a flexible organic electrochemical transistor according to claim 1, characterized in that: The insulating layer ink is made of two different batches of PDMS: Sylgard 184 and SE 1700 are mixed and then centrifuged to disperse uniformly. Then, isopropyl alcohol is added to the mixture as a diluent and centrifuged again to obtain a uniform insulating layer ink.

3. The 3D printing ink for a flexible organic electrochemical transistor according to claim 1, characterized in that: The dielectric layer ink was prepared by dispersing PSSNa and d-sorbitol in aluminum chloride and glycerol, followed by magnetic stirring on a hot plate and finally stirring at room temperature to remove gel bubbles.

4. A 3D printing method for preparing a flexible organic electrochemical transistor using the 3D printing ink for a flexible organic electrochemical transistor according to any one of claims 1 to 3, characterized in that: The substrate ink, electrode ink, active layer ink, insulating layer ink and dielectric layer ink are prepared; the size of the organic electrochemical transistor is drawn, and then the ink printing parameters are set and printed using a 3D printing system.

5. The 3D printing method for preparing a flexible organic electrochemical transistor according to claim 4, characterized in that: The parameters of the base ink were set as follows: nozzle 27 G, pressure 70 Pa, and speed 25 mm / s.

6. The 3D printing method for preparing a flexible organic electrochemical transistor according to claim 4, characterized in that: The parameters of the electrode ink are set as follows: nozzle 30 G, pressure 70 Pa, speed 10 mm / s, and resolution between 120 and 150 μm.

7. The 3D printing method for preparing a flexible organic electrochemical transistor according to claim 4, characterized in that: The parameters of the PEDOT:PSS channel active layer ink were as follows: nozzle 34 G, pressure 80 Pa, speed 5 mm / s, and resolution 100-120 μm. The gate active layer ink parameter settings are: nozzle 30 G; pressure 200 Pa; speed 15 mm / s; resolution 150 μm.

8. The 3D printing method for preparing a flexible organic electrochemical transistor according to claim 4, characterized in that: The parameters of the insulating layer ink are as follows: nozzle 30 G, pressure 200 Pa, speed 15 mm / s, and resolution 150 μm; the parameters of the dielectric layer ink are as follows: nozzle 32 G, pressure 500 Pa, speed 10 mm / s, and resolution 120 μm.