Self-Powered Flexible Piezo-Sensor and MicroLED: Toward Commercialization

This seminar introduces two recent progresses of self-powered flexible devices; piezo-sensors and microLED. The first part will introduce flexible inorganic piezoelectric membrane that can detect the minute vibration of membrane for self-powered acoustic sensor and blood pressure monitor. Speaker recognition has received spotlight as personalized voice-controlled interface, smart home, biometric authentication. The conventional speaker recognition was realized by a condenser type microphone, which detects sound by measuring the capacitance value between two conducting layers. The condenser type microphone, however, has critical demerits such as low sensitivity, high power consumption, low recognition rate and an unstable circuit due to the large gain amplification. Herein, we reported a machine learning-based acoustic sensor by mimicking the basilar membrane of human cochlear. Highly sensitive self-powered flexible piezoelectric acoustic sensor with a multi-resonant frequency band was employed for voice recognition. Convolutional Neural Network (CNN) were utilized for speaker recognition, resulted in a 97.5% speaker recognition rate with the 75% reduction of error rate compared to that of the reference MEMS microphone. In addition, wearable piezoelectric blood-pressure sensors (WPBPS) were developed for continuous non-invasive arterial pressure monitoring. WPBPS achieves a high normalized sensitivity (0.062 kPa−1), and fast response time (23 ms). The transfer function of a linear regression model converts flexible piezoelectric sensor signals into blood pressure values. Clinical validation of WPBPS was performed on 35 subjects/175 measurements, that satisfies international standard of blood pressure measuring devices.<br/>The second part will discuss the highly efficient flexible micro LED for displays and biomedical applications. Flexible displays can be easily affixed anywhere, such as on the surfaces of human skin, clothes, automobiles and buildings. III-V inorganic LEDs have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to OLED. However, due to the brittle property of inorganic materials, III-V LED limits its applications for flexible electronics. Here we introduce the flexible GaAs/GaN microLED using innovative micro-vacuum transfer technology. The superb properties of flexible inorganic LED enable not only full-color displays and wearable phototherapy patches like hair growth, melanogenesis inhibition and pancreas cancer. In addition, combining with optogenetic mouse models, flexible microLED stimulates the neurons of motor cortex for manipulating mouse body movements and synchronized electromyogram (EMG) signals.