Xiaoguang Gao,Lin Yuan,Chengzhen Xue,Xiaoliang Zhang,Xuejuan Meng,Xiaochun Li
Flexible piezoresistive sensors with a porous structure that are used in the field of speech recognition are seldom characterized by both high sensitivity and ease of preparation. In this study, a piezoresistive sensor with a porous structure that is both highly sensitive and can be prepared by using a simple method is proposed for speech recognition. The preparation process utilizes the interaction of bubbles generated by ethanol evaporation and active agents with polydimethylsiloxane to produce a porous flexible substrate. This preparation process requires neither templates nor harsh experimental conditions such as a low temperature and a low pressure. Furthermore, the prepared piezoresistive sensor has excellent properties, such as a high sensitivity (27.6 kPa–1), a satisfactory response time (800 μs), and a good stability (10,000 cycles). When used for speech recognition, more than 1500 vocalizations and silent speech signals obtained from subjects saying numbers from “0” to “9” were collected by the sensor for training a convolutional neural network model. The average accuracy of the recognition reached 94.8%. The simple preparation process and the excellent performance of the prepared flexible piezoresistive sensor endow it with a wide application prospect in the field of speech recognition.
Symmetry typically characterizes the impact of a liquid droplet on a solid surface, where uniform spreading is followed by radial retraction. Breaking this symmetry traditionally relies on engineering surface properties. Here, we introduce an alternative approach to achieve asymmetric droplet impact by incorporating a pair of bubbles into the liquid droplet, resulting in the coexistence of spreading and retraction. The asymmetric dynamics originate from the anisotropic capillary effects that can be adjusted by varying the volume fraction of bubbles and the impact velocity. The early onset of retraction enhances upward liquid momentum, facilitating prompt droplet takeoff and significantly reducing both the contact area (up to 50%) and contact time (up to 60%). This reduction also diminishes heat exchange between the droplet and the surface. Our findings pave the way for applications that capitalize on reduced contact times through droplet engineering, eliminating the need for surface modifications.
危险品化学品经营许可证（带存储）