CN111438944B

CN111438944B - A method for preparing nano-scale electrojet nozzle based on SU-8 gel electrolysis

Info

Publication number: CN111438944B
Application number: CN202010253691.1A
Authority: CN
Inventors: 殷志富; 杨雪; 贾炳强; 胡伟; 李露
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2020-04-02
Filing date: 2020-04-02
Publication date: 2021-10-01
Anticipated expiration: 2040-04-02
Also published as: CN111438944A

Abstract

The invention relates to the preparation of nano-scale electric jet nozzles, in particular to a method for preparing nano-scale electric jet nozzles based on the SU-8 glue electrolysis method. The invention adopts SU-8 glue as the material of the electric jet needle, and creates necessary conditions for the formation of nano-cracks by means of incomplete drying and overexposure. Taking the graphene straight line as the induction pattern, under the electrolysis of high voltage electricity, a linear nano-channel with relatively uniform size is formed under the induction pattern. After thermocompression bonding, UV lithography, and electrode fabrication steps, the final nanoscale electric jet nozzle is formed.

Description

Method for preparing nanoscale electric jet nozzle based on SU-8 glue electrolysis method

Technical Field

The invention relates to preparation of an electric jet printing spray needle, in particular to a method for preparing a nanoscale electric jet spray needle by using an SU-8 glue electrolysis method.

Background

The direct writing method is a printing technique that does not require a mask, a mold, or additional auxiliary equipment. The method has shown a huge application prospect in the fields of model machine development, small-batch production, model repair and the like. The direct writing method mainly comprises the methods of fused deposition rapid prototyping, photocuring prototyping, three-dimensional powder bonding, selective laser sintering, electric jet printing and the like. In the method, the electro-hydraulic fluid dynamic effect is used for electro-fluidic printing, namely, ink is drawn by a high-voltage electric field, internal charges are concentrated at the meniscus of the nozzle, so that electric jet is drawn, and a three-dimensional structure can be formed by combining three-dimensional movement of the printing platform. Experiments have shown that the diameter of the electro-jet can be 2-3 orders of magnitude smaller than the inner diameter of the needle. Therefore, only electrojet printing is currently capable of achieving nano-scale precision printing.

The inherent properties of electrojet printing make electrojets advantageous as follows. First, the electrojet has extremely high material adaptability to the printing material. I.e., the same print resolution, the electro-jet printing may use a thicker print head. Second, the cost of electrojet printing is lower. Because under the same line width of writing directly, the shower nozzle size that the electrojet printing needs is bigger, so the electrojet printing is difficult for appearing ink jam, shower nozzle and makes difficult scheduling problem for the equipment of electrojet itself and printing cost are lower. The advantages of electrojet printing have led to widespread industrial and academic interest in this approach once it has been introduced. At present, the electric jet printing is practically applied in the fields of thin film deposition, solar cells, diode manufacturing, flexible electronic printing and the like.

While electro-jet printing has great advantages over other direct-write techniques in micron and sub-micron precision printing, electro-jet printing still presents challenges in nano-scale resolution printing. Because the jet size is directly determined by the inner diameter of the spray needle, the nanoscale electric jet nozzle still needs to be manufactured at present for realizing nanoscale resolution printing. Typically, the electrojet printing apparatus need not be placed in an ultra-clean room. This makes nanometer internal diameter shower nozzle easily receive granule, the ink impurity influence in the environment, leads to the shower nozzle jam phenomenon. For the nanometer inner diameter spray head, the influence of the surface tension of the liquid causes that the cleaning liquid is extremely difficult to enter the nanometer channel, so that the nanometer spray head is difficult to clean by adopting a flushing mode. Usually, once the nano-sprinkler is clogged, the only solution is to replace the entire sprinkler with a new one. The traditional nano-scale electric jet flow nozzle is quite complex in manufacturing process, high in cost and dependent on expensive equipment. This indicates that the cost of nanoscale resolution direct writing based on electrojet printing is still high at present. Nanoscale electrojet nozzle fabrication has become a bottleneck limiting the development of electrojet printing in the direct-write field of nanoscale structures. In order to expand the application range of the electric jet printing, the development of a low-cost nano-scale electric jet nozzle process is urgently needed.

Disclosure of Invention

The invention aims to solve the technical problems of high cost, complex process and the like of the traditional method for preparing the nanoscale electric jet nozzle, and provides a novel process for preparing the nanoscale electric jet nozzle based on an SU-8 electrolysis method.

The invention provides a method for forming a nanoscale electric jet flow nozzle by using graphite as an induction graph, applying high-voltage current to form a nano channel on an SU-8 substrate which is not completely crosslinked, and finally forming the nanoscale electric jet flow nozzle through hot-press bonding and electrode manufacturing, wherein the whole nozzle manufacturing comprises the following steps:

1. fabrication of microstructures for nanoscale electrofluidic nozzles

2. Nano-channel fabrication of nano-scale electrojet nozzles

3. Nanoscale electrojet nozzle encapsulation

Compared with the existing method for manufacturing the jet printing needle, the method has the advantages of extremely simple preparation process, extremely low cost, high yield, no dependence on expensive equipment, convenient operation and suitability for batch processing.

Drawings

FIG. 1 is a schematic diagram of a process for fabricating a nanoscale electrojet nozzle.

Fig. 2 is a structural diagram of the finally manufactured nanoscale electro-jet needle.

In the figure: 1 an electric jet nozzle silicon substrate; 2, an electric jet spray head SU-8 glue substrate; 3, inducing graphite strips; 4 silver paste connecting points; 5, nano-channels of the electric jet nozzle; 6 electric jet nozzle SU-8 glue cover plate; 7 an electric jet spray head liquid storage tank; 8 nanometer channel section; 9 an electrojet nozzle electrode.

Detailed Description

The following detailed description of the invention is provided in connection with the accompanying drawings.

1. Fabrication of microstructures for nanoscale electrofluidic nozzles

(1) An SU-8 photoresist 2 with a thickness of about 20 μm was spin-coated on a silicon substrate 1 at a spin-coating speed of 3000 rpm for 30 seconds. And (3) incompletely prebaking the SU-8 glue, wherein the prebaking temperature is 70 ℃, and the prebaking time is 4-5 minutes. The incomplete prebaking can increase the conductivity of SU-8, ensure that linear and uniform-size nano cracks can be formed in the step 2, and prevent the bifurcation phenomenon of the nano cracks.

(2) Aligning the photoetching mask plate with the substrate of the SU-8 glue, and overexposing the SU-8 glue for 15 minutes. Overexposure can promote embrittlement of the SU-8 glue, and is a necessary condition for forming the nano-cracks in the step 2. After developing the SU-8 gum base (development time 4-5 minutes), the micro-structures of the nanoscale electro-jet nozzle shown in fig. 1a can be formed.

2. Nano-channel fabrication of nano-scale electrojet nozzles

(1) At the position shown in fig. 1B, a graphene straight line 3 is drawn with an 8B pencil as a nano-crack inducing pattern. And silver paste 4 is adopted to respectively fix a wire at two ends of the graphene straight line.

(2) High voltage electricity (2300 plus 2500V/cm) is applied to two ends of the lead, the SU-8 glue which is not completely dried has certain conductivity, and the overexposure causes the SU-8 glue to be embrittled, the current flows along the linear direction of the induced graphene, the molecular chain of the SU-8 glue is broken under the action of the high voltage electricity, electrolysis is carried out, and a soluble substance is formed. After ultrasonic cleaning with alcohol, a nano channel 5 of the nano-scale electric jet nozzle shown in fig. 1c can be formed right under the induction pattern. The depth and width range of the nano-cracks is between 300 and 500 nanometers.

3. Nanoscale electrojet nozzle encapsulation

(1) A layer of SU-8 glue with a thickness of about 10 μm was spin-coated on a PDMS substrate at a spin-coating speed of 8000 rpm for 30 seconds. And completely drying the SU-8 adhesive, wherein the pre-drying temperature is 90 ℃, and the pre-drying time is 15 minutes.

(2) And aligning the PDMS and the silicon substrate, and then carrying out hot-press bonding, wherein the bonding temperature is 50 ℃, the bonding pressure is 0.5 MPa, and the bonding time is 15 minutes. After bonding, the PDMS substrate is removed, and the SU-8 glue is transferred to the nanoscale electric jet head to form the nanoscale electric jet head cover plate 6 shown in FIG. 1 d.

(3) And (3) completely exposing the nanoscale electric jet nozzle by using a mask plate, wherein the exposure time is 6-8 minutes. After development (development time 4 minutes), a nanoscale electrojet nozzle liquid storage tank 7 can be formed.

(4) As shown in fig. 1e, the electrospray nozzle was cut at a position perpendicular to the nanochannel, exposing a nanochannel cross-section 8. The copper wire 9 is soldered to the reservoir location as shown in fig. 1e using a spot welder to form the final nanoscale electro-fluidic nozzle (as shown in fig. 2).

The same principles apply to other related technical fields, including equivalent methods using the contents of the present invention and the accompanying drawings, or applied directly or indirectly.

Claims

1. a method for preparing nanoscale electric jet nozzle based on SU-8 glue electrolysis method, is characterized in that, comprises the following steps:

1. Fabrication of microstructures of nanoscale electrojet nozzles

(1) Spin-coat a layer of SU-8 photoresist with a thickness of 20 microns on the silicon substrate, the spin-coating speed is 3000 rpm, and the spin-coating time is 30 seconds; The pre-baking temperature is 70 degrees Celsius, and the time is 4-5 minutes;

(2) Align the photolithography mask with the SU-8 glue base, and over-expose the SU-8 glue for 15 minutes; after developing the SU-8 glue base for 4-5 minutes, a nanometer scale is formed. The microstructure of the electrojet nozzle;

2. Nano-channel fabrication of nano-scale electrojet showerheads

(1) On the electric jet nozzle, use an 8B pencil to draw a graphene line as a nano-crack induction pattern; use silver paste to fix a wire at each end of the graphene line;

(2) Apply 2300-2500 volts/cm high voltage at both ends of the wire; after ultrasonic cleaning with alcohol, cracks with nanoscale width and depth are formed directly below the induced pattern, forming a nanochannel of the electric jet nozzle;

3. Nano-scale electrojet nozzle packaging

(1) Spin coat a layer of SU-8 glue with a thickness of 10 microns on the PDMS substrate, the spin coating speed is 8000 rpm, and the spin coating time is 30 seconds; the SU-8 glue is completely dried, and the pre-baking temperature is 90 Celsius, the pre-baking time is 15 minutes;

(2) After aligning the PDMS and the silicon substrate, perform thermocompression bonding, the bonding temperature is 50 degrees Celsius, the bonding pressure is 0.5 MPa, and the bonding time is 15 minutes; after bonding, remove the PDMS substrate, SU-8 The glue will be transferred to the nano-scale electro-jet nozzle to form a nano-scale electro-jet nozzle cover;

(3) Use the mask to fully expose the nano-scale electro-jet nozzle, and the exposure time is 6-8 minutes; after developing for 4 minutes, a nano-scale electro-jet nozzle reservoir is formed;

The electro-jet nozzle is cut at a position perpendicular to the nano-channel to expose the cross-section of the nano-channel; the copper wire is welded to the position of the liquid reservoir by a spot welding machine to form the final nano-scale electro-jet nozzle.