Scalable Production of Ultrafine Polyaniline Fibres for Wearable Electronics

High performance conducting polymer fibres are highly demanded in fields from advanced fibrous devices to frontier fabric electronics. Recently, a joint research team, led by Prof. Xiaoming TAO and Dr Yang CHAI, reported a scalable good solvent exchange strategy to produce ultrafine polyaniline (PAni) fibres. This work was published at Nature Communications. The first authors are Dr. Fang Bo and Mr. Jianmin Yan.

Processing conducting polymers into macroscopically fibrous materials makes it possible to translate their nano-object features to human-friendly products in a continuous manner. Primarily due to the large diameters, the performance and expectations of most achieved continuous conducting polymer fibres (CPFs) have been limited by their insufficient electroactive surfaces and weak tensile strength. Tao’s group report a good solvent exchange strategy in a modified wet spinning technique to prepare the ultrafine PAni fibres (UFPFs) at the large scale. Beyond conventional wet spinning protocol, they replaced poor solvents by good solvents as the coagulation bath to decrease the viscosity of gel protofibres, which were subject to an ultrahigh drawing ratio and reduced to an ultrafine morphology. In the modified one-step wet spinning process, they used good solvents as the coagulation bath to realize the mass production of UFPFs. A decreasing of diameter from ~0.1 mm to ~4.7 µm was observed, which is a record small value in the achieved wet-spun CPFs. The ultrafine fibre shows a smooth surface, highly crystallized microstructures, and uniform electrical properties. Moreover, such an impressive drawing ratio enables a very high production efficiency of UFPFs beyond 40 meters per minute.

UFPFs show impressive mechanical performance and energy storage abilities. UFPFs have a modulus of 29.89±5.6 GPa, and a strength of 1080±71 MPa, at least one order of magnitude higher than that of CPFs with larger diameters. They used polyvinyl alcohol (PVA)-H₃PO₄ gel electrolyte and two UFPF electrodes to construct a micro capacitor to evaluate the electrochemical activity of UFPFs. The area capacitance is between 1008 and 1666 mF cm^-2 at the current densities between 0.32 and 3.18 mA cm^-2, outperforming previously reported thick CPFs and other electrodes, and approaching to that of PAni nanowires. Benefitting from the favorable energy and charge storage performance of UFPFs, they demonstrated a high-performance all-solid organic electrochemical transistor (OECT), which is very soft, and shows favorable amplification performance with a high on-off current ratio (>10³) at low voltages (<1 V). The all-solid OECT functioned to respond to mechanical deformation as a tactile sensor.