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. 2022 Apr 19;13(1):2101.
doi: 10.1038/s41467-022-29773-9.

Scalable production of ultrafine polyaniline fibres for tactile organic electrochemical transistors

Bo Fang #  1   2 , Jianmin Yan #  3   4 , Dan Chang  5 , Jinli Piao  3   6 , Kit Ming Ma  3   6 , Qiao Gu  7   8 , Ping Gao  7   8 , Yang Chai  9   10 , Xiaoming Tao  11   12
Affiliations

Scalable production of ultrafine polyaniline fibres for tactile organic electrochemical transistors

Bo Fang et al. Nat Commun. .

Abstract

The development of continuous conducting polymer fibres is essential for applications ranging from advanced fibrous devices to frontier fabric electronics. The use of continuous conducting polymer fibres requires a small diameter to maximize their electroactive surface, microstructural orientation, and mechanical strength. However, regularly used wet spinning techniques have rarely achieved this goal due primarily to the insufficient slenderization of rapidly solidified conducting polymer molecules in poor solvents. Here we report a good solvent exchange strategy to wet spin the ultrafine polyaniline fibres. The slow diffusion between good solvents distinctly decreases the viscosity of protofibers, which undergo an impressive drawing ratio. The continuously collected polyaniline fibres have a previously unattained diameter below 5 µm, high energy and charge storage capacities, and favorable mechanical performance. We demonstrated an ultrathin all-solid organic electrochemical transistor based on ultrafine polyaniline fibres, which operated as a tactile sensor detecting pressure and friction forces at different levels.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Scalable production of UFPFs.
a Schematic of the good solvent exchange strategy to prepare UFPFs in a modified wet spinning protocol. In the case of poor solvent exchange (light orange region, upper panel), PAni molecules are rapidly solidified into thick gels and protofibres with rough crystallized particles. In the case of good solvent exchange (light blue region, lower panel), the formed gels with low viscosity occur an impressive gel extension and are slenderized into ultrafine fibers. b Schematic of the modified wet spinning process. c Scanning electron microscope (SEM) image of the marked region in (b), showing the sharp necking behavior of gel PAni fibers. The close observation of region 1 (d), region 2 (e), and region 3 (f) in the marked zone of (c), illustrating the sharply necking process of PAni gels. g Photograph of a 5.4-kilometers-long UFPF collected in two hours. Scale bars: c 20 µm, d 2 µm, e 10 µm, g 150 mm.
Fig. 2
Fig. 2. Mechanism and mechanical properties of UFPFs.
a SEM images of the PAni fibers produced in different solvating species. Specifically, the upper four panels show the fibers prepared from poor solvents, and the lower two panels show the fibers fabricated from good solvents. b Raman spectra of PAni fibers after placing in air for four weeks. c The diffusivity from PAni dispersions (in m-cresol) to various solvating species. d The viscosity of PAni gels formed in various solvating species. e Mechanics simulation results of extension behaviors of PAni gel fibers at different interfacial pressure. Comparing to the blue regions, the elements in blue regions are subject to larger stress. f Typical tensile stress-strain curves of UFPFs. g Ashby plot comparing the mechanical strength of UFPFs to previously reported CPFs. Scale bars in a: Water, Ethanol, EA, Acetone 20 µm (left) 10 µm (right); NMP 20 µm (left) 5 µm (right), DMF 20 µm (left) 2 µm (right).
Fig. 3
Fig. 3. Energy and charge storage capacities of UFPFs.
a Schematic of a micro capacitor constructed using two UFPF electrodes on a substrate. b Cyclic voltammetry curves with the increasing scan rates from 10 to 20, 50, 80, and 100 mV s−1. c Galvanostatic charge/discharge curves at various current densities increasing from 0.32 to 0.63, 1.59, and 3.18 mA cm−2. d The area capacitance of UFPFs compared to previously reported electrodes. e Cycle galvanostatic charge/discharge curves during 120 cycles between 0 and 0.6 V at 1.59 mA cm−2. f The relationship between current and voltage at a slow rate of 10 mV s−1. g The charge storage capacity of UFPFs comparing to other charge storage materials.
Fig. 4
Fig. 4. Demonstration and characterization of all-solid organic electrochemical transistor based on UFPFs.
a Schematic of the all-solid OECT composed of three polymer layers, one silver wire as the gate electrode, and one UFPF as the drain-source channel. b Cross-section SEM image and schematic of OECT. The yellow break lines direct the charge flow along the fiber chains (green solid lines). c Transmittance of the OECT in the region of visible light. A typical output curve (d), transfer curve (e), and power consumption in operation (f) of OECT. Scale bars: b 20 µm.
Fig. 5
Fig. 5. Electrical response of the all-solid OECT to mechanical deformations.
a Schematic of the mechanism explaining the response to the action of external pressure. b Relative drain-source change (ΔIDS/IDS0) and sensitivity as a function of pressure. c Response time of the all-solid OECT when pressing (rising edge) and releasing (falling part) under the instantaneous pressure of 17.8 kPa. d Cyclic response at three different pressure levels (0.92, 6.8, and 22.2 kPa). e, Schematic of the working principle of the response to friction. f Cyclic response at three different frictions (1.84, 4.69, and 5.55 kPa). g An enlarged curve of the marked part in (f). h Cyclic response at different friction speeds from 4, 6, 8, 10, 15, to 20 mm s−1.
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