Yuan-Quan Chen

An intelligent artificial throat with sound-sensing ability based on laser induced graphene

Traditional sound sources and sound detectors are usually independent and discrete in the human hearing range. To minimize the device size and integrate it with wearable electronics, there is an urgent requirement of realizing the functional integration of generating and detecting sound in a single device. Here we show an intelligent laser-induced graphene artificial throat, which can not only generate sound but also detect sound in a single device. More importantly, the intelligent artificial throat will significantly assist for the disabled, because the simple throat vibrations such as hum, cough and scream with different intensity or frequency from a mute person can be detected and converted into controllable sounds. Furthermore, the laser-induced graphene artificial throat has the advantage of one-step fabrication, high efficiency, excellent flexibility and low cost, and it will open practical applications in voice control, wearable electronics and many other areas.

Graphene-Paper Pressure Sensor for Detecting Human Motions

Pressure sensors should have an excellent sensitivity in the range of 0-20 kPa when applied in wearable applications. Traditional pressure sensors cannot achieve both a high sensitivity and a large working range simultaneously, which results in their limited applications in wearable fields. There is an urgent need to develop a pressure sensor to make a breakthrough in both sensitivity and working range. In this paper, a graphene-paper pressure sensor that shows excellent performance in the range of 0-20 kPa is proposed. Compared to most reported graphene pressure sensors, this work realizes the optimization of sensitivity and working range, which is especially suitable for wearable applications. We also demonstrate that the pressure sensor can be applied in pulse detection, respiratory detection, voice recognition, as well as various intense motion detections. This graphene-paper pressure sensor will have great potentials for smart wearable devices to achieve health monitoring and motion detection.

A Flexible Ultrasound Transducer Array with Micro-Machined Bulk PZT

This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications.

Highly sensitive and portable gas sensing system based on reduced graphene oxide

Graphene has been widely used in gas-sensing applications due to its large specific surface area and strong adsorption ability. Among different forms of graphene used as gas-sensing materials, reduced graphene oxide is one of the most convenient and economical materials to integrate with Si-based electronics, which is very important to graphene-based gas sensors. In addition, the stacking structure of graphene oxide flakes facilitates absorption and detection of gas molecules. Based on reduced graphene oxide, a highly sensitive and portable gas-sensing system was demonstrated here. Solution-based graphene oxide was cast on a chip like a TF memory card and then reduced thermally. A signal acquisition system was designed to monitor resistance variation as a sign of gas concentration. This miniature graphene-based gas sensor array demonstrates a new path for the use of graphene in gas-detection technologies. And the creation of a sensitive and portable graphene gas sensor also shows great potential in fields such as medicine and environmental science.

Large-Scale and High-Density pMUT Array Based on Isolated Sol-Gel PZT Membranes for Fingerprint Imaging

In this work, we proposed a novel ultrasonic transducer array based on an array of 50 × 50 piezoelectric micromachined ultrasonic transducers (pMUTs). The structure was specially designed for fingerprint imaging application. The pMUTs array were fabricated with isolated piezoelectric lead zirconate titanate (PZT) cells to reduce the crosstalk between adjacent units, and released by deepsilicon etching from the back side. The cell size and pitch of pMUTs were 50 μm and 100 μm, respectively. Layer-by-layer annealing method was used instead of one-time annealing during the fabrication of sol-gel based PZT film. The resonance frequency of the pMUT was about 24.82 MHz which agreed well with simulated 25.02 MHz. Besides, the effective electro-mechanical coupling coefficient (keff) and mechanical quality factor (Q factor) of the transducer were 0.1293 and 198, respectively. The equivalent circuit of the transducer was established and analyzed. The fitted admittance circle agreed well with the experimental result. This demonstration of pMUTs array has profound potential for large-scale, high-density, and high-frequency fingerprint imaging.

Tunable and wearable high performance strain sensors based on laser patterned graphene flakes

Tunable and wearable strain sensors with high gauge factor (GF) and large strain range based on laser patterned graphene flakes (LPGF) are demonstrated in this paper. The performance can be adjusted by laser patterning, resulting in a preferable GF (up to 457) or strain range (over 100%), both of which are significantly higher than most of the state-of-the-art graphene strain sensors. Most importantly, the tunable strain sensors with high GF and large strain range can be fabricated simultaneously by a one-step laser patterning. These tunable strain sensors can meet the demands of monitoring both subtle and large human motions, indicating that they will have great potentials in health care, voice recognition, gesture control and many other areas.

Electrical thermal acoustic point source based on mems technology

This work demonstrated, for the first time, an electro-thermoacoustic (ETA) point source based on Point-Contact-Structure (PCS) realized by MEMS technology based on suspended aluminum nanowires. The novel type of device improves the performance at low frequency down to 500 Hz, enhances the efficiency of ETA device by over 7 folds and widen the 3 dB range of low frequency range comparing to conventional suspended aluminum nanowires (AW) ETA devices. The highest sound pressure level (SPL) achieved by PCS acoustic device is 67 dB at 1 cm with 74 mW AC input. The novel device works in a less than ± 3 dB fluctuation mode which is realized by the enhancement of SPL at low frequency.