Flexible sensors have recently attracted much attention for potential applications in motion measurement and wearable health monitoring. In this paper, an environment-friendly, economic, and high-performance paper-based self-inductive folding displacement sensor (PSIFS) was proposed, with displacement resolution of 20 μm and wide measurement range of 43.2 mm. The sensor sensitivity could reach 4.44% mm⁻¹ with the maximum deviation of 0.00904 in experiments. The sensing mechanism based on inductance variation due to three-dimensional deformation of planar inductor coil and structural design principle under two dimensions of sensitivity and size were proposed and studied. The folding method to enhance sensitivity was proposed and 3 times sensitivity enhancement could be achieved by once folding. Multiple breathing states and motion states of the human joints could be recognized. The proposed simple paper-based sensor, folding method to increase sensitivity, and structural design model may provide a way for the research of flexible sensors.

Flexible pressure sensors offer the advantages of flexibility, low cost, and easy to large area fabrication, and they have wide applications in many fields. This work proposes a flexible capacitive pressure sensor that exhibits a sandwich‐like structure, a good performance, and a simple process. Multi‐walled carbon nanotube (MWNT) is used to fabricate the two electrodes of the sensor because this low cost material possesses good mechanical and electronic properties. Meanwhile, MWNT naturally forms numerous micro–nano structures that can enhance the sensitivity of a sensor. In addition, the dielectric layer of the sensor composed of parylene C (poly(chloro‐p‐xylylene)) is sandwiched between the two electrodes. The experimental results show that the pressure sensor demonstrates high sensitivity and a rapid response. The average sensitivity is 1.33 kPa ^–1 at a pressure that ranges from 0 to 758 Pa and the response time reach to millisecond level. Given that low cost, good property and simple process, the sensor has wide application prospects in electronic skins, health monitoring devices, and other wearable electronic products.

The demand for waterproofing of polymer (parylene) coating encapsulation has increased in a wide variety of applications, especially in the waterproof protection of electronic devices. However, parylene coatings often produce pinholes and cracks, which will reduce the waterproof effect as a protective barrier. This characteristic has a more significant influence on sensors and actuators with movable parts. Thus, a defect filling method of micro-nano composite structure is proposed to improve the waterproof ability of parylene coatings. The defect filling method is composed of a nano layer of Al₂O₃ molecules and a micro layer of parylene polymer. Based on the diffusion mechanism of water molecules in the polymer membrane, defects on the surface of polymer encapsulation will be filled and decomposed into smaller areas by Al₂O₃ nanoparticles to delay or hinder the penetration of water molecules. Accordingly, the dense Al₂O₃ nanoparticles are utilized to fill and repair the surface of the organic polymer by low-rate atomic layer deposition. This paper takes the pressure sensor as an example to carry out the corresponding research. Experimental results show that the proposed method is very effective and the encapsulated sensors work properly in a saline solution after a period of time equivalent to 153.9 days in body temperature, maintaining their accuracy and precision of 2 mmHg. Moreover, the sensors could improve accuracy by about 43% after the proposed encapsulation. Therefore, the water molecule anti-permeability encapsulation would have broad application prospects in micro/nano-device protection.

We present a method based on a microfluidic chip that produces continuous jetting of alginate microfiber in the atmosphere to facilitate its collection and assembly. Through the analysis of the factors influencing the microfiber jetting, the principle and some microfluidic chip design criteria are discussed. A special nozzle is designed near the chip outlet, and deionized water is introduced into the microchannel through the nozzle to increase the flux and thus to prevent drop formation around the outlet which impedes the continuous jetting of microfiber. The experiments have reported the effectiveness of the proposed structure and shown that the introduction of sheath flow promotes the stability of the flow field in the microchannel and does not affect the morphology of microfiber. Simulations of velocity and pressure distribution in the microchannel are also conducted. Further, the jetting microfibers are collected and assembled into various 3D complex fiber-based macroscopic structures through patterning or reeling. Since the proposed structure is rather simple and can be easily integrated into other complex structures without adding more soft-lithographical steps, microfibers with various morphology and function can be synthesized and collected in a single chip, which can be applied to various fields, such as tissue engineering, biotechnology, and drug discovery.