Flexible and skin-attachable vibration sensors have been studied for use as wearable voice-recognition electronics. However, the development of vibration sensors to recognize the human voice accurately with a flat frequency response, a high sensitivity, and a flexible/conformable form factor has proved a major challenge. Here, we present an ultrathin, conformable, and vibration-responsive electronic skin that detects skin acceleration, which is highly and linearly correlated with voice pressure. This device consists of a crosslinked ultrathin polymer film and a hole-patterned diaphragm structure, and senses voices quantitatively with an outstanding sensitivity of 5.5 V Pa
−1
over the voice frequency range. Moreover, this ultrathin device (<5 μm) exhibits superior skin conformity, which enables exact voice recognition because it eliminates vibrational distortion on rough and curved skin surfaces. Our device is suitable for several promising voice-recognition applications, such as security authentication, remote control systems and vocal healthcare.
Numerous wearable devices were developed
to measure bioelectric
signals for continuous healthcare monitoring. The electrode, which
interconnects electronics and the human body, significantly affects
the signal quality. Although Ag/AgCl electrodes have been commonly
used, noble-metal electrodes are more promising in terms of long-term
reusability and flexibility. However, the signal-to-noise ratio (SNR)
of noble metals is still insufficient for highly accurate biosignal
acquisition. In this study, we propose an approach to enhance the
electrical characteristics of a noble-metal skin electrode by surface
modification using gold nanoparticles. The process parameters for
nanoparticle deposition were optimized to maximize the surface area,
thereby significantly improving the SNR of the electrode. The SNR
value was increased by 51% in electrocardiogram and by 63% in electromyogram
(EMG). We also propose an approach to quantify the motion artifact
by spectral analysis, and the high flexibility of our electrode reduced
the motion noise by 95% compared to the conventional Ag/AgCl electrode.
The enhanced electrode interface paves the way for analyzing complex
biosignals such as EMG and electroencephalogram in wearable applications.
Numerous wearable sensors have been developed for a variety of needs in medical/healthcare/wellness/sports applications, but there are still doubts about their usefulness due to uncomfortable fit or frequent battery charging. Because the size or capacity of battery is the major factor affecting the convenience of wearable sensors, power consumption must be reduced. We developed a method that can significantly reduce the power consumption by introducing a signal repeater and a special switch that provides power only when needed. Antenna radiation characteristics are an important factor in wireless wearable sensors, but soft material encapsulation for comfortable fit results in poor wireless performance. We improved the antenna radiation characteristics by a local encapsulation patterning. In particular, ultra-low power operation enables the use of paper battery to achieve a very thin and flexible form factor. Also, we verified the human body safety through specific absorption rate simulations. With these methods, we demonstrated a wearable infant sleep position sensor. Infants are unable to call for help in unsafe situations, and it is not easy for caregivers to observe them all the time. Our wearable sensor detects infants' sleep positions in real time and automatically alerts the caregivers when needed.
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