One-Step Laser Direct-Printing Process of a Hybrid Microstructure for Highly Sensitive Flexible Piezocapacitive Sensors.

Microstructures can effectively improve the sensing performance of flexible piezocapacitive sensors. Simple, low-cost fabrication methods for microstructures are key to facilitating the practical application of piezocapacitive sensors. Herein, based on the laser thermal effect and the thermal decomposition of glucose, a rapid, simple, and low-cost laser direct-printing process is proposed for the preparation of a polydimethylsiloxane (PDMS)-based electrode with a hybrid microstructure. Combining the PDMS-based electrode with an ionic gel film, highly sensitive piezocapacitive sensors with different hybrid microstructures are realized. Due to the good mechanical properties brought about by the hybrid microstructure and the double electric layer induced by the ionic gel film, the sensor with a porous X-type microstructure exhibits an ultrahigh sensitivity of 92.87 kPa-1 in the pressure range of 0-1000 Pa, a wide measurement range of 100 kPa, excellent stability (>3000 cycles), fast response time (100 ms) and recovery time (101 ms), and good reversibility. Furthermore, the sensor is used to monitor human physiological signals such as throat vibration, pulse, and facial muscle movement, demonstrating the application potential of the sensor in human health monitoring. Most importantly, the laser direct-printing process provides a new strategy for the one-step preparation of hybrid microstructures on thermal curing polymers.

High-Efficiency Copper Removal by Nitrogen Plasma-Assisted Picosecond Laser Processing.

Copper (Cu) removal efficiency is a key parameter in the processing of Cu-based electronic devices. Herein, a nitrogen plasma-assisted picosecond (ps) laser process for Cu removal is presented. Based on the cleaning and activation effect of nitrogen plasma on the surface of Cu film in ps-laser ablation, the removal efficiency can be significantly improved. Theoretically, the interaction mechanism between Cu and the ps-laser under the action of the plasma flow field is investigated by the dual temperature model (TTM) and finite element analysis (FEA). Meanwhile, the experimental results show that the angle of the plasma flow significantly affects the laser ablation of Cu. Small-angle plasma helps to improve the ps-laser processing precision of Cu, while large-angle plasma can effectively improve the ps-laser processing efficiency of Cu. Under the laser fluence of 2.69 J/cm2, the removal depth of the Cu film by a 30° plasma-assisted ps-laser is 148% higher than that by the non-plasma-assisted ps-laser, which indicates the application potential of nitrogen plasma in improving the laser ablation process.