High-performance flexible strain sensors with a low cost, simple structure, and large-scale fabrication methods have a high demand in soft robotics, wearable devices, and health monitoring. Here, a direct-ink-writing-based 3D printing method, which fabricates structural layers in an efficient, layered manner, was developed to fabricate a stretchable and flexible strain sensor composed of carbon black/silicone elastomer (CB/PDMS) composites as the strain-sensing elements and electrodes. As the sensing element, the CB/PDMS composite had a sensitivity of 5.696 in the linear strain detection range of 0 to 60%, with good stability and low hysteresis. The flexible strain sensor demonstrates potential in monitoring various human motions, including large deformation motions of the human body, and muscle motions with facial micro-expressions.

Respiratory monitoring is crucial for evaluating health status and identifying potential respiratory diseases such as respiratory failure, bronchitis, and pneumonia. Humidity sensors play a significant role in this regard, and efforts are being made to improve their performance. However, achieving ideal sensor parameters such as sensitivity, detection range, and response speed is challenging. In this work, we propose a flexible preparation method for a double-layer humidity sensor using PDMS as a substrate and a GNP/MWCNT composite material as a sensor element. This sensor exhibits high sensitivity (1.4 RH-1), a wide detection range (20–90%), ultra-fast response (0.35 s) and recovery (2.5 s), high repetitiveness (500 cycles), good long-term stability, and excellent flexibility. Due to these advantages, this sensor has potential applications in real-time clinical and home medical care, such as accurate human respiratory monitoring and non-invasive skin humidity monitoring. Hence, this humidity sensor can be a powerful tool to monitor respiratory moisture levels for diagnosing and treating respiratory diseases effectively.

Bionic electronic skin with human sensory capabilities has attracted extensive research interest, which has been applied in the fields of medical health diagnosis, wearable electronics, human–computer interaction, and bionic prosthetics. Electronic skin tactile pressure sensing required high sensitivity, good resolution and fast response for sensing different pressure stimuli. In particular, there were still great challenges in the detection of wide pressure and the preparation of sensitive unit microstructures. Here, the direct-write printing of Weissenberg principle to fabricate GNPs/MWCNT filled conductive composite flexible pressure sensors on PDMS substrates was proposed. The effects of platform moving speed, microneedle rotation speed and the number of direct-write times on the line width of the pressure sensitive structure were investigated based on orthogonal experiments, and the optimal direct-write printing parameters were obtained. The performance of the S-shaped polyline pressure sensor was tested, in which the sensitivity could reached 0.164 kPa⁻¹, and the response/recovery time was 100 ms and 100 ms respectively. The capture cases of objects of different quality and objects with flat/curved surfaces were successively demonstrated to exhibit its excellent sensitivity, stability and fast response performance. This work may paved the road for future integration of high-performance electronic skin in smart robotics and prosthetic solutions.

The extensive water pollution caused by production activities is a key issue that needs to be addressed in the aquaculture industry. The dynamic monitoring of water quality is essential for understanding water quality and the growth of fish fry. Here, a low-cost, low-noise, real-time monitoring and automatic feedback biomimetic robotic fish was proposed for the dynamic monitoring of multiple water quality parameters in aquaculture. The biomimetic robotic fish achieved a faster swimming speed and more stable posture control at a swing angular velocity of 16 rad/s by using simulation analysis. A fast swimming speed (0.4 m/s) was achieved through the control of double-jointed pectoral and caudal fins, exhibiting various types of movements, such as straight swimming, obstacle avoidance, turning, diving, and surfacing. As a demonstration of application, bionic robotic fish were placed in a lake for on-site water sampling and parameter detection. The relative average deviations in water quality parameters, such as water temperature, acidity and alkalinity, and turbidity, were 1.25%, 0.07%, and 0.94%, respectively, meeting the accuracy requirements for water quality parameter detection. In the future, bionic robotic fish are beneficial for monitoring water quality, fish populations, and behaviors, improving the efficiency and productivity of aquaculture, and also providing interesting tools and technologies for science education and ocean exploration.

In order to achieve the high-precision and high-efficiency machining of micro-channels for hard and brittle materials, the authors innovatively proposed a new technology called template-based electrophoretically assisted micro-ultrasonic machining (TBEPAMUSM). This technology transfers the micro-channel shape punch-pin to the workpiece material through micro-ultrasonic machining to form a micro-channel. At the same time, it uses the electrophoretic properties of ultra-fine abrasive particles to ensure the existence of abrasive particles in the machining area by applying a DC electric field. According to the new technology machining principle, a machine tool of TBEPAMUSM was designed and developed. The machine tool hardware adopts a C-shaped structure, including a marble platform, an ultrasonic vibration system, a micro three-dimensional motion platform, a working fluid tank, and a pressure sensor. The machine tool intelligent control system is developed based on LabVIEW, including the initialization module, fast positioning module, constant force tool setting module, constant force control machining module, and real-time coordinate display module. Micro-channels with different structures are machined on single-crystal silicon and soda-lime glass using the designed machine tool and the developed control system. The results show that: when electrophoresis assistance is applied in machining, the edge chipping phenomenon of the micro-channel is significantly reduced, the surface roughness is reduced by about 20%, and the machining efficiency is increased by about 4%.