A self-powered piezoelectret sensor based on foamed plastic garbage for monitoring human motions

Constructing piezoelectret based on foamed plastic garbage is an advisable strategy for obtaining self-powered flexible electromechanical sensors with good performances.Herein,a self-powered piezoelectret sensor with basic material of low density polyethylene(LDPE)foamed plastic garbage is proposed,with characteristics of easy fabrication,excellent flexibility,and high equivalent piezoelectric coefficient d33 value up to~1,100 pC/N.The output stability is verified by continuously stimulating a sensor for~180,000 cycles under low and high applied pressure,and the variations of peak outputs are less than 5.5%.Applications for measuring low-and high-pressure signals from human body are achieved.Assembled with a wristband,a sensor is demonstrated for detecting the human pulse waves.Moreover,real time human sitting information is wirelessly monitored with a smart chair based on 4 pixels sensors array.

Scalable and eco-friendly flexible loudspeakers for distributed human-machine interactions

Flexible loudspeakers that can be easily distributed in the surrounding environment are essential for creating immersive experiences in human-machine interactions,as these devices can transmit acoustic information conveniently.In this paper,we present a flexible electret loudspeaker that offers numerous benefits,such as eco-friendly,easy fabrication,flexible customization,strong durability,and excellent outputs.The output sound pressure level(SPL)and frequency response characteristic are optimized according to the simulation and experiment results.At a distance of 50 meters,a large-size loudspeaker(50×40 cm^(2))can produce an average SPL of 60 dB(normal SPL range of human voices is between 40 to 70 dB).The frequency response of our loudspeaker is high and relatively consistent up to 15 kHz,which covers the normal frequency range of human voices(<8 kHz).As demonstrated in this work,our loudspeakers can be used for scalable applications,such as being integrated with curtains or hung up like posters,offering a promising and practical solution for creating better human-machine interaction experiences.