posted on 2024-01-08, 16:34authored byQianqian Hu, Lian Zhou, Xingchen Ma, Xiaoqing Zhang
Nowadays,
humans rely increasingly on smart electronics to address
grand challenges and to improve life conditions in the era of digitalization
and big data. However, electronics often have a limited lifespan,
and they may bring electronic waste problems after their service.
To mitigate this problem, environmentally sustainable methods of electronic
device production and disposal are highly recommended, where advanced
functional materials should be redesigned with improved sensing performance
over the entire operational life while also being naturally degradable
at the end. Herein, a biodegradable and flexible bifunctional electroacoustic
transducer was fabricated with the utilization of cellular polylactic
acid (PLA) ferroelectret films, possessing a small acoustic impedance
of ∼0.02 MRayl which is quite close to that of air and a high
figure of merit (FOM: d33·g33) of ∼11 GPa–1. Such
devices have a prominent signal-to-noise ratio (SNR) of ∼23.5
dB @1 kHz and can work either as a microphone by direct piezoelectric
effect or a loudspeaker by reverse piezoelectric effect in air medium.
When used as a microphone, the flexible device exhibits a prominent
receiving sensitivity up to 4.2 mV/Pa (∼−47.5 dB/ref.
1 V/Pa) at 1 kHz. When served as a loudspeaker, it is capable of yielding
high sound pressure levels (SPLs) ranging from 60
to 103 dB (ref. 20 μPa) in a broad frequency range of 1–80
kHz with an active area of 3.14 cm2. Additionally, the
electrical response curve of the device is very flat in a wide frequency
range from 300 to 3000 Hz. With the high-performance acoustic-electric
conversion capacity, the PLA ferroelectret-based flexible and filmlike
electroacoustic transducer was used to realize accurate speech recognition
and control, providing a strong impetus for its advanced and eco-friendly
applications in the era of the internet of things (IoT) and artificial
intelligence.