CN104934513A - Organic field effect transistor biosafety flexible photosensitive sensor and preparation method - Google Patents

Abstract

The invention relates to a biosafety flexible photosensitive sensor of an organic field effect transistor (OFET) and a preparation method thereof, comprising: a polylactic acid (PLA) film as a dielectric layer, a gold film evaporated on the bottom of the PLA film as a gate electrode, and An organic semiconductor layer is evaporated on the top of the PLA film as a conductive layer, and gold films isolated from each other are evaporated on the top of the conductive layer as a source electrode and a drain electrode. Compared with the prior art, the OFET in the present invention has the advantages of low cost, excellent photosensitive performance, flexibility and biological safety.

Description

Organic field effect transistor biosafety flexible photosensitive sensor and preparation method

technical field

The invention relates to a photosensitive sensor, in particular to a biosafety flexible photosensitive sensor based on an organic field effect transistor and a preparation method thereof.

Background technique

Optical sensors based on organic field-effect transistors (OFETs) have excellent performance and are widely used in a wide range of applications, including photodetection, photoswitches, phototrigger amplifiers, and pattern imaging. However, traditional OFET photosensitive sensors require organic semiconductor materials to have both high mobility and good photosensitive performance, which limits the large-scale application of OFET photosensitive sensors. On the other hand, the structural design of OFET devices can also be used to obtain sensors with excellent performance. For example, Zhenan Bao’s team at Stanford University reported an OFET based on a polydimethylsiloxane (PDMS dielectric layer) with a complex microstructure. The OFET has very high pressure sensitivity. Our team also reported a temperature-sensitive sensor prepared by using the interface between the dielectric layer and the organic semiconductor layer in the OFET, which can be applied to the temperature sensing of artificial skin. The sensors obtained by these methods are not Furthermore, organic semiconductors are required to be sensitive to stimuli or signals, so they have a wide range of material applicability. Moreover, photosensitive sensors based on this method have not been reported.

Photosensitive sensors with both flexibility and biosafety have broad application prospects. For example, John A.Rogers reported the use of flexible photosensitive sensors to imitate the compound eye structure of insects, and prepared flexible spherical imaging with excellent performance such as wide viewing angle and low aberration. equipment; he also reported the integration of biologically safe micro-LED light sources, photosensitive sensors and other electronic devices into the brains of mice, thus pioneering the study of optogenetic behavior of the nervous system of organisms. However, the materials used in the above devices include PDMS and inorganic silicon-based semiconductor materials, and their biosafety and flexibility need to be improved.

Contents of the invention

The object of the present invention is to provide a biosafety flexible photosensitive sensor and a preparation method of an organic field effect transistor with excellent photosensitive performance and biosafety in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A biosafety flexible photosensitive sensor of an organic field effect transistor, comprising:

PLA film as a dielectric layer,

The gold film evaporated on the bottom of the PLA film is used as the gate electrode,

An organic semiconductor layer is evaporated on top of the PLA film as a conductive layer,

On top of the conductive layer, isolated gold films are deposited as source and drain electrodes.

The thickness of the PLA film is 1-5 μm.

The thickness of the gold thin film used as the gate electrode is 50-100nm.

The thickness of the organic semiconductor layer is 50-100 nm, and the material is dinaphthothiophene.

The distance between the source and the drain is 10-500 μm.

The preparation method of the biosafety flexible photosensitive sensor of the organic field effect transistor adopts the following steps:

a) Cleaning of the substrate: use acetone and isopropanol to ultrasonically clean the silicon wafer substrate in sequence, then rinse with absolute ethanol and deionized water, and finally dry the substrate surface with nitrogen;

b) Surface anti-adhesive treatment of the substrate: spin coating a solution of (tridecafluoro-1,1,2,2-tetrahydrooctane)-trichlorosilane (FOTS) in chloroform with a volume concentration of 1-5% To the surface of the above-mentioned cleaned silicon chip as an anti-sticking layer;

c) thermally evaporating gold onto the silicon wafer under a vacuum of 7×10 ^-4 Pa to form a gate electrode;

d) The product of c) is vertically placed in a 50 g/L PLA chloroform solution, and slowly pulled away from the solution surface at a rate of 15 μm/s to obtain a PLA film as an OFET dielectric layer;

e) thermally evaporating the dinaphthothiophene onto the above PLA film under a vacuum of 7×10 ^-4 Pa;

f) Using the same method as c), thermally evaporate gold onto the product of e) by means of a mask, as the source and drain electrodes of the OFET;

g) peeling off the PLA film from the FOTS-treated silicon wafer to obtain a flexible photosensitive sensor.

Compared with the prior art, the present invention has the following advantages:

1. PLA and DNTT are used as the substrate and dielectric layer and organic semiconductor material of OFET respectively. Because the chemical polar groups in PLA have an attraction and capture effect on the carriers in DNTT, this effect can be absorbed by light Influence, so that the prepared OFET has photosensitive performance, the optical switch ratio reaches 10 ⁴ times, can be used as a photosensitive transistor, and can be applied to pattern imaging;

2. The prepared OFET has both flexibility and biocompatibility, and it can maintain normal performance when the device is rolled on an object with a radius of less than 800 μm; PLA itself is a polymer material with excellent biocompatibility, and DNTT accounts for the mass fraction of OFET It is less than 1%, so the overall biological safety of OFET is good. In the co-culture experiment of device extract and L929 cells, the growth rate of cells is higher than 80%;

3. The preparation process of this technology is simple, does not require sophisticated preparation instruments, is low in cost, and is convenient for large-scale production.

Description of drawings

Fig. 1 is the OFET work performance prepared by the present invention, namely its output characteristic curve.

Fig. 2 shows the flexibility of the OFET prepared in the present invention, and its mobility varies with the crimp radius.

Fig. 3 shows the biocompatibility of the OFET prepared in the present invention, and the growth rate of co-cultured cells with it.

Figure 4 shows the photosensitive performance of the flexible OFET prepared by this technology, that is, the change of its transfer characteristic curve with light intensity.

Figure 5 is the output characteristic curve of the flexible OFET prepared by this technology as a phototransistor when no field voltage is applied.

Figure 6 shows the imaging application of the flexible OFET photosensor prepared by this technology to the five-pointed star pattern.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

A biosafety flexible photosensitive sensor of an organic field effect transistor, including a PLA film with a thickness of 1-5 μm as a dielectric layer, a gold film with a thickness of 50-100 nm evaporated on the bottom of the PLA film as a gate electrode, and a gold film on the top of the PLA film The evaporation thickness is 50-100nm, and the material is a dinaphthothiophenone organic semiconductor layer as the conductive layer, and a gold film isolated from each other is evaporated on the top of the conductive layer as the source and drain, and the distance between the source and the drain is 10-500μm.

The Au gate electrode is shielded by a mask and then thermally evaporated. Its width is slightly larger than the channel width between the top Au source and drain, which not only ensures that the organic semiconductor in the channel is in the field voltage, but also minimizes the bottom gate electrode. The overlap with the top source/drain reduces the risk of OFET device breakdown leakage. The molecular formulas of the dielectric material PLA and the organic semiconductor material DNTT used in the OFET are shown in Figure 2. The molecular weight of PLA is 100,000-200,000. After purchase, it is purified by dissolution and precipitation. The solvent is chloroform, and the precipitating agent is methanol. DNTT is synthesized according to the following steps:

In step 1, the purity of all chemical reagents is analytically pure. Tetrahydrofuran was subjected to dehydration treatment before use, and all reactions were carried out in an anhydrous and oxygen-free environment under the protection of argon. 2.87 mL (21 mmol) of trimethylethylenediamine was added to 35 mL of tetrahydrofuran, and mixed with n-butyl lithium in n-hexane (1.59 M concentration, 13.2 mL) at minus 30°C. After stirring the mixed solution at the same temperature for 15 minutes, slowly add dropwise (5 minutes to complete) the tetrahydrofuran solution of 2-naphthaldehyde (2.0g 2-naphthaldehyde is added in 10mL tetrahydrofuran), and then add 24.15mL concentration of 38.4mmol The n-butyllithium n-hexane solution was stirred at minus 30°C for 3.5 hours. After adding excess dimethyl disulfide (5.67 mL, 64 mmol) and stirring at room temperature for 2 hours, 20 mL of hydrochloric acid (1M concentration) was added. The final mixture was stirred for 10 hours and extracted with 60 mL of dichloromethane. The extract was dried over MgSO4 and then vacuum dried. The solid residue was purified using a chromatographic column to obtain a yellow solid 1a (1.49 g), and the chromatographic liquid was a mixture of n-hexane and ethyl acetate (volume ratio: 9:1).

Step 2, add 0.39g of zinc powder to 10mL of tetrahydrofuran, slowly add 0.66mL of titanium tetrachloride and heat to reflux for 1.5 hours. After the solution was lowered to room temperature, a tetrahydrofuran solution of 1a was slowly added (0.405g of 1a was added to 10ml of tetrahydrofuran), and the mixture was condensed and refluxed for 10 hours. After the temperature dropped to room temperature, it was diluted with 30 mL of saturated aqueous sodium bicarbonate solution and 30 mL of dichloromethane, and stirred for 3.5 hours. Filtration was performed using celite, and the filtrate was divided into an organic layer and an aqueous layer. The aqueous layer was extracted with 60 mL of dichloromethane, and several layers were dried with MgSO4 and then dried in vacuo. Purified by washing and running plate (silica gel plate) with dichloromethane to obtain 2a (0.299 g) as yellow crystals.

Step 3, 0.2235g 2a and 4.87g iodine were sequentially added to 15mL chloroform and refluxed for 21 hours. After the temperature dropped to room temperature, 20 mL of saturated aqueous sodium bisulfite solution was added, and the precipitate was filtered out and washed with water and chloroform. The obtained crude product was purified by vacuum sublimation to obtain a yellow solid, namely DNTT.

The prepared OFET works well, and its transistor output characteristic curve is shown in Fig. 1 .

Example 2

The OFET prepared by this technology has excellent flexibility, can be rolled and folded, and can still maintain the electrical properties of the device in the rolled state. In order to characterize the working situation of the OFET in the coiled state in the present invention, at first the OFET device is tightly wound on cylindrical objects with different radii, and the transistor performance of the OFET is tested in this state. The radius parameter selected in this example is from Infinity (i.e. the OFET is in a flat state) to 800чm. Fig. 2 shows the variation of the mobility of the OFET with its crimping radius. It can be seen that when the device is crimped to a radius of 800 чm, its mobility is only reduced by 4%, indicating that the OFET device in the present invention has excellent flexibility.

Example 3

Soak the OFET sample prepared by the present invention in 2 mL of RPMI1640 solution, keep it at 37°C for 24 or 48 hours, then filter the solution, dilute it to 1 to 1/8 times, and finally mix it with calf serum solution with a volume fraction of 10%. L929 cells at a concentration of 1×10 ⁴ /mL were mixed with the above solution for 7 days, and fresh solution was added every 24 hours. The L929 cells used as the blank control group were cultured in the cell culture medium without OFET extract for 7 days. Add 5 mg/mL of MTT solution to the above cell culture liquid, after 3.5 hours, filter the generated precipitate, dissolve it in dimethyl sulfoxide (DMSO), and test its optical density (optical density, OD). The cytocompatibility of the OFET sample can be expressed by the relative growth ratios (RGR) of the co-cultured cells, which is equal to the OD value of the OFET sample divided by the OD value of the blank control group. The better the capacity. Figure 3 shows the growth of L929 cells in co-culture experiments with different extraction times and different dilutions of OFET extraction liquid. The RGR value is greater than 80% in all cases, indicating that the OFET prepared by this technology has good biological safety.

Example 4

Use a broad-spectrum LED collimated light source to irradiate the above-mentioned OFET, adjust the irradiation light intensity from 0.5-100mW/cm2, test the output characteristic curve and transfer characteristic curve of OFET with a semiconductor parameter meter, and obtain the current, mobility and threshold voltage of OFET as a function of Changes in light intensity. Figure 6 shows the transfer characteristic curves of OFET under different light intensities, and it can be seen that the optical switch ratio of the OFET photosensor prepared by the present invention is 10 ² -10 ⁴ . Fig. 4 shows the change of the source/drain current-voltage curve with the light intensity of the device under the condition of no field voltage, which shows that the device prepared by the present invention can be used as a photosensitive transistor at the same time.

Cover the 10×10 OFET device matrix with an object with a specific shape pattern (in this example, a five-pointed star-shaped cardboard), and then place the device matrix under light to test the electrical parameters of each device element such as current, mobility and The ratio of the threshold voltage etc. to the electrical parameters of each element when there is no object coverage gives the photosensitive imaging of the OFET device matrix for the object. The matrix signal output of the OFET device shown in Figure 5 clearly shows the pattern of a five-pointed star, indicating that the OFET photosensitive device prepared by the present invention has good pattern imaging capability.

Claims (6)

1. a bio-safety flexible photosensitive transducer for organic field effect tube, is characterized in that, comprising:

As PLA (PLA) film of dielectric layer,

Bottom PLA film, the gold thin film of evaporation is as gate electrode,

At PLA film top evaporation organic semiconductor layer as conductive layer,

The gold thin film mutually completely cut off at conductive layer top evaporation is as source electrode and drain electrode.

2. the bio-safety flexible photosensitive transducer of a kind of organic field effect tube according to claim 1, is characterized in that, described PLA film thickness is 1-5 μm.

3. the bio-safety flexible photosensitive transducer of a kind of organic field effect tube according to claim 1, is characterized in that, the gold thin film thickness as gate electrode is 50-100nm.

4. the bio-safety flexible photosensitive transducer of a kind of organic field effect tube according to claim 1, is characterized in that, the thickness of described organic semiconductor layer is 50-100nm, and material is dinaphtho thienone.

5. the bio-safety flexible photosensitive transducer of a kind of organic field effect tube according to claim 1, is characterized in that, the distance between described source electrode and drain electrode is 10-500 μm.

6. the preparation method of the bio-safety flexible photosensitive transducer of the organic field effect tube according to any one of claim 1-5, is characterized in that, the method adopts following steps:

A) clean of substrate: use acetone, at the bottom of isopropyl alcohol ultrasonic cleaning silicon wafer-based successively, then use absolute ethyl alcohol and deionized water rinsing, finally dry up substrate surface with nitrogen;

B) the surface anti sticking process of substrate: be that (13 fluoro-1,1,2,2-tetrahydrochysene octane)-trichlorosilane (FOTS) solution in chloroform of 1-5% is spun to above-mentioned clean silicon chip surface as adherent layer by volumetric concentration;

C) 7 × 10 ^-4gate electrode is formed by hot for gold evaporation to silicon chip under the vacuum of Pa;

D) product c) is vertically placed in the PLA chloroformic solution of 50g/L, slowly lifts with the speed of 15 μm/s and leave solution surface, obtain the PLA film as OFET dielectric layer;

E) 7 × 10 ^-4under the vacuum of Pa, by the thermal evaporation of dinaphtho thienone on above-mentioned PLA film;

F) use c) identical method, the mode utilizing mask plate to block by hot for gold evaporation on product e), as source electrode and the drain electrode of OFET;

G) PLA film being taken off from there being the silicon chip of FOTS process, obtaining flexible photosensitive transducer.