Laser Direct Writing of Highly Ordered Two-Level Hierarchical Microstructures for Flexible Piezoresistive Sensor with Enhanced Sensitivity

With the development of micro-nano manufacturing technology, various hierarchical microstructures (HMs) are used to improve the sensitivity and measurement range of flexible pressure sensors. However, the fabrication of highly ordered HMs in simple, fast, and low-cost ways remains a great challenge. In this work, laser direct writing technology is used to fabricate highly ordered HMs to enhance the sensitivity of flexible piezoresistive sensors. The HMs show a lateral expansion with the increasing pressure due to good flexibility and small force bearing areas, resulting in more significant change in contact area than the single-level microstructures, which leads to an enhanced sensitivity. Two case studies are conducted to verify the performance of the sensor with laser processed HMs. Experimental results show that the pulsating blood pressure signal of radial artery can be detected by attaching the sensor on the wrist. When the sensor is attached on the neck, it can also detect the vibration signal of vocal cord when speaking. These results successfully demonstrate the potential of laser processing in fabricating highly ordered HMs to achieve highly sensitive flexible piezoresistive sensors for various applications, such as wearable health monitoring and human-computer interactions.