A method for fabricating nanofluid memristors based on nano-milling array nanochannel structures

Abstract

A method for fabricating a nanofluidic memristor based on a nanochannel array structure fabricated by nanomilling is disclosed, belonging to the field of memristor fabrication technology. The method comprises: fabricating the upper microchannel using ultraviolet lithography; fabricating the lower microchannel using a flexible mask on a silicon wafer surface via ultraviolet lithography, dissolving and removing the photoresist in the non-exposed areas to expose the silicon substrate, fabricating the microchannel structure on the silicon substrate, and removing all the photoresist to obtain a silicon substrate with microchannels; nanomilling is performed using an atomic force microscope system and a two-dimensional piezoelectric ceramic actuator; transferring the silicon wafer with convex microchannels as a template yields a PDMS wafer with microchannels; a second transfer is performed using a silicon wafer with a nanochannel array as a template to obtain a PDMS wafer with nanochannels and microchannels; and bonding the two PDMS wafers using oxygen plasma treatment. This invention offers a simple, rapid, efficient, structurally stable, and consistent method that can be mass-produced and is biocompatible.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of memristor preparation, and particularly relates to a nanofluid memristor preparation method based on nanomilling array nanochannel structure. BACKGROUND

[0002] At present, computer systems are developed based on the Von Neumann computing architecture, and computation and storage are highly separated, so that the processor cannot fully exert the computing capacity. Compared with other hardware, the memristor with the resistance non-volatility characteristics can well match the neural network to realize the neuromorphic computing. The nanofluid memristor has the advantages of simple preparation process, durability and good retention characteristics, and has a broad application prospect in future neuromorphic computing.

[0003] The geometric shape has a significant influence on the electrical performance of the nanochannel. When the characteristic size of the nanochannel approaches the Debye length, the double electric layer of the nanochannel will overlap, which affects the ion transmission in the nanochannel, and thus various phenomena occur. Therefore, high-quality processing of the size-controllable nanochannel is of great significance to improve the performance of the fluid memristor. At present, the methods suitable for preparing the nanofluidic device-based fluid memristor mainly include electron beam lithography (EBL), focused ion beam lithography (FIB), nanoimprint lithography (NIL) and self-assembly technology. EBL and FIB can etch silicon-based materials with a resolution as low as 10 nm, but are expensive. The NIL process needs to be heated, and the thermal expansion of the plastic material will cause dimensional errors in the pattern transfer process. Using AFM nanomilling silicon substrate can obtain nanochannels with controllable size and good consistency, and the nanofluidic memristor can be quickly prepared by using the nanochannels as a template for transfer. SUMMARY

[0004] The application aims to solve the problems of high cost and poor precision of the existing nanofluidic device preparation method, and provides a nanofluid memristor preparation method based on nanomilling array nanochannel structure.

[0005] To achieve the above-mentioned purpose, the technical solutions adopted by the application are as follows:

[0006] A nanofluid memristor preparation method based on nanomilling array nanochannel structure, the method comprises the following steps:

[0007] Step 1: Microchannel structure fabrication: The upper microchannel is fabricated using ultraviolet lithography. After exposure and development, a convex microchannel structure is obtained. The lower microchannel is fabricated by preparing a flexible mask on the silicon wafer surface using ultraviolet lithography. The photoresist in the non-exposed areas dissolves and falls off, exposing the silicon substrate. Reactive ion etching (RIE) is performed using a mixed gas of SF6 and O2 to fabricate the microchannel structure on the silicon substrate. After removing all the photoresist using Remover PG stripper, a silicon substrate with microchannels is obtained.

[0008] Step Two: Nanochannel Structure Fabrication: Nanomilling is achieved using a combination of a commercial atomic force microscope (AFM) system and a two-dimensional piezoelectric ceramic actuator. During nanomilling, the sample rotates, and the fabrication is achieved through relative motion. The rotational motion of the sample is driven by a sinusoidal signal with a 90° phase difference, and the motion of the sample in the horizontal plane is achieved by the combined motion in the X and Y directions. There is no material buildup at the edges of the nanogrooves, making them suitable for fabricating nanofluidic memristors. A nanochannel array is fabricated on the silicon substrate with microchannels from Step One using AFM nanomilling.

[0009] Step 3: Structure transfer: After transferring the silicon wafer with convex microchannels as a template, a PDMS sheet with microchannels can be obtained; after transferring the silicon wafer with nanochannel array as a template once, the PDMS obtained from the first transfer is used as a template, PDMS is poured in, and then heated on a hot plate at 120°C for 30 minutes. The cured PDMS is then peeled off from the mold to obtain a PDMS sheet with nanochannels and microchannels.

[0010] Step 4: Bonding: Bond the PDMS sheet with microchannels from Step 3 to the PDMS sheet with nanochannels and microchannels using oxygen plasma treatment.

[0011] Furthermore, in step one, in the ultraviolet lithography technology, a negative photoresist (SU-82015) produced by MicroChem Inc. of the United States is used. The photoresist is first spin-coated on the silicon substrate at a speed of 500 r / min for 5 s, and then spin-coated at a speed of 4000 r / min for 120 s.

[0012] Furthermore, in step two, the driving voltages in the X and Y directions are 100V and 150V, respectively, and the normal load and driving frequency are 12μN and 2000Hz, respectively.

[0013] Furthermore, in step three, the material used for transfer printing is Sylgard 184 polydimethylsiloxane (PDMS) produced by DowCorining, Inc., USA. The mass ratio of PDMS to curing agent is selected as 10:1. The PDMS and curing agent are stirred evenly, then poured onto the mold and left to stand until all air bubbles in the PDMS are removed. The mold after removing the air bubbles is then placed on a hot plate at 120°C and heated for 30 minutes. Finally, the PDMS with the replicated structure is gently peeled off from the mold to obtain the PDMS sheet with the structure.

[0014] Further, in step four, the prepared PDMS sheets are treated with an oxygen plasma cleaner manufactured by Diener Electronics, Germany, at a power of 80W for 30 seconds. Following alignment markings, the PDMS sheets with microchannels and nanochannel arrays are bonded together. The bonded PDMS sheets are then placed on a hot plate at 95°C for 20 minutes for adhesion. The actual fluid memristor is shown below. Figure 5 As shown.

[0015] The advantages of this invention over the prior art are: the method for preparing nanofluidic memristors has the advantages of simple process, fast and efficient operation, stable structure, good consistency and mass replication, and good biocompatibility. Attached Figure Description

[0016] Figure 1 Flowchart for the fabrication of nanofluidic memristors;

[0017] Figure 2 This is a schematic diagram of a nanofluid memristor structure;

[0018] Figure 3 This is a schematic diagram of an AFM-based vibration-assisted nanofabrication system;

[0019] Figure 4 A typical AFM morphology image of a secondary transfer of nanogrooves;

[0020] Figure 5 This is a physical image of a fluid memristor;

[0021] Figure 6 The graph shows the measurement results of the fluid memristor IV. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0023] This invention primarily uses an atomic force microscope (AFM) as the processing equipment to scribing and processing a silicon wafer with microchannels to obtain nanogrooves. The structure on the silicon wafer surface is used as a template, and PDMS is used for two transfers to obtain PDMS with microchannels and nanochannels. This is then bonded to another PDMS wafer with microchannels to obtain a nanofluid memristor with a nanochannel array.

[0024] Example 1:

[0025] The specific implementation method for fabricating nanofluidic memristors is as follows:

[0026] (1) Microchannel structure fabrication: The fabrication process of nanofluidic memristors is as follows Figure 1 As shown, (a1)-(a3) illustrate the fabrication process of the upper microchannel, and (b1)-(b4) illustrate the fabrication process of the lower microchannel and nanochannel. The upper microchannel was fabricated using ultraviolet lithography with negative photoresist (SU-82015) manufactured by MicroChem, USA. The photoresist was first spin-coated onto the silicon substrate at 500 rpm for 5 seconds, then at 4000 rpm for 120 seconds. After exposure and development processes, a convex microchannel structure was obtained, as shown... Figure 1 As shown in (a1). The fabrication of the lower microchannel is as follows. Figure 1 As shown in (b1)-(b2), a flexible mask is prepared on the surface of a silicon wafer by ultraviolet lithography. The photoresist in the non-exposed area dissolves and falls off, exposing the silicon substrate. RIE etching is performed using a mixed gas of SF6 and O2 to process a microchannel structure on the silicon substrate.

[0027] (2) Fabrication of nanochannel structures: Nanomilling platforms such as Figure 3 As shown, the process is mainly achieved by a combination of a commercial atomic force microscope (AFM) system and a piezoelectric ceramic actuator. During nanomilling, the sample rotates, and the machining is achieved through relative motion. The rotational motion of the sample is accomplished by a two-dimensional piezoelectric ceramic actuator driven by a sinusoidal signal with a 90° phase difference. The motion of the sample in the horizontal plane is achieved by the combined motion in the X and Y directions. The driving voltages in the X and Y directions are 100V and 150V, respectively, and the normal load and driving frequency are 12μN and 2000Hz, respectively. No material accumulation occurs at the edges of the nanogrooves, making it suitable for fabricating nanofluidic memristors. Through AFM nanomilling, nanometers with microchannel structures are fabricated on silicon substrates (…). Figure 1 b2) is used to fabricate nanochannel arrays, such as Figure 1 (b3) and Figure 2 As shown.

[0028] (3) Structure Transfer: The material used for transfer was Sylgard 184 manufactured by Dow Corning, USA, with a PDMS to curing agent mass ratio of 10:1. The PDMS and curing agent were stirred evenly, then poured onto a mold and allowed to stand until all air bubbles in the PDMS were removed. The mold, after removing the air bubbles, was then placed on a hot plate at 120°C and heated for 30 minutes. Finally, the PDMS with the replicated structure was gently peeled off the mold to obtain a PDMS sheet with the structure. Figure 1 As shown in (a2)-(a3), after transferring a silicon wafer with convex microchannels as a template, PDMS with microchannels can be obtained. The secondary transfer process is the same as the primary transfer process, as follows: Figure 1 As shown in (b4), after a silicon wafer (b3) with a nanochannel array is used as a template for a first transfer, the PDMS obtained from the first transfer is used as a template. PDMS is poured into the template and heated on a hot plate at 120°C for 30 minutes. The cured PDMS is then peeled off from the mold to obtain a PDMS sheet (b4) with nanochannels and microchannels. AFM images of AFM nanomilling for grooves, the raised structure obtained from the first PDMS transfer, and the groove obtained from the second PDMS transfer are shown below. Figure 4 As shown.

[0029] (4) Bonding: The PDMS chips were bonded using an oxygen plasma treatment bonding method. The prepared PDMS chips were treated with an oxygen plasma cleaner (Diener Electronics, Germany) at 80W for 30 seconds. The PDMS chips were then bonded according to the alignment marks, and the bonded PDMS chips were placed on a hot plate at 95°C for 20 minutes for adhesion. The actual fluid memristor is shown below. Figure 5 As shown.

[0030] (5) Electrical performance testing: A high-precision electrometer (Keithley 6430) manufactured by Keithley, USA, was used to measure the current values ​​on both sides of the channel. The voltage increment interval was 1V, and each voltage increase was followed by a 2s interval. The electrolyte solution was a mixture of 1mM KCl solution and ionic liquid BmimPF6. Typical results of the nanofluidic memristor IV measurement are as follows: Figure 6 As shown, the fabricated nanofluidic memristor exhibits excellent memristor performance.

Claims

1. A method for fabricating a nanofluid memristor based on nano-channel array fabrication using nanomilling, characterized in that: The method is: Step one: micro-channel structure processing: the preparation of the upper micro-channel is realized by using ultraviolet lithography technology, after exposure and development, the convex micro-channel structure is obtained; the preparation of the lower micro-channel is to prepare a flexible mask on the surface of the silicon wafer by ultraviolet lithography, the photoresist in the non-exposed area is dissolved and falls off, exposing the silicon substrate, using SF6 and O2 mixed gas for reactive ion etching, the micro-channel structure is processed on the silicon substrate, after removing the photoresist with Remover PG, the silicon substrate with micro-channel is obtained; Step two: nano-channel structure processing: nano-milling is realized by combining commercial atomic force microscope system and two-dimensional piezoelectric ceramic actuator; during nano-milling, the sample rotates, and the processing is realized by relative motion; the rotation of the sample is completed by the two-dimensional piezoelectric ceramic actuator driven by sinusoidal signals with a phase difference of 90°, and the movement of the sample in the horizontal plane is realized by the synthesis of X and Y directions; by AFM nano-milling, the nano-channel array is processed on the silicon substrate with micro-channel in step one; Step three: structure transfer: after transferring the silicon wafer with convex micro-channel as a template, the PDMS sheet with micro-channel can be obtained; after one transfer using the silicon wafer with nano-channel array as a template, the PDMS obtained by one transfer is used as a template, poured into PDMS, and placed on a hot plate at 120℃ for heating for 30 minutes, and the cured PDMS is peeled off from the mold to obtain a PDMS sheet with nano-channel and micro-channel; Step four: bonding: the PDMS sheet with micro-channel in step three and the PDMS sheet with nano-channel and micro-channel are bonded by oxygen plasma treatment.

2. The method for fabricating a nano-fluidic memristor based on nano-milling array nanochannel structure according to claim 1, wherein: In step one, in the ultraviolet lithography technology, a negative photoresist is used, the photoresist is first spin-coated on the silicon substrate at a speed of 500 r / min for 5 s, and then at a speed of 4000 r / min for 120 s.

3. The method of claim 1, wherein the method comprises: In step two, the driving voltages in X and Y directions are 100 V and 150 V respectively, the normal load and driving frequency are 12 μN and 2000 Hz respectively.

4. The method for fabricating a nano-fluidic memristor based on nanomilling array nanochannel structure according to claim 1, wherein: In step three, the material used for transfer is polydimethylsiloxane, the mass ratio of PDMS to curing agent is selected as 10:1; the PDMS and curing agent are uniformly stirred, then poured into the mold and left until all the bubbles in the PDMS are removed; then the mold after removing the bubbles is placed on a hot plate at 120℃ for heating for 30 minutes; finally, the PDMS after copying structure is gently peeled off from the mold to obtain the PDMS sheet with structure.

5. The method of claim 1, wherein the method comprises: In step four, the prepared PDMS sheet is treated by an oxygen plasma cleaning machine at a power of 80 W for 30 seconds, and then the PDMS sheet with micro-channel and the PDMS sheet with nano-channel array are aligned and bonded, and then the bonded PDMS sheet is placed on a hot plate at 95℃ for 20 minutes.

Images