Liwei Lin (Advisor)

Research Advised by Professor Liwei Lin

Lin Group:  List of Projects | List of Researchers

A Multimodal Self-heating Flexible Seat Sensor for Heathcare Monitoring

Peisheng He
Yande Peng
Liwei Lin
2021

We report a self-healable, flexible, and multimodal sweat sensor based on laser-induced graphene electrodes for healthcare monitoring application. A transfer printing and laser engraving process has been developed to conduct a high-throughput patterning process of various materials on a self-healable substrate. The prototype device is capable of simultaneous detection of pH, uric acid, and tyrosine, which are important indicators for skin and metabolic disorders. Furthermore, this work has made advancements as compared with the state-of-art works: (1) maintaining sensitivity under large...

A Single Chip Directional Loudspeadker Based on PMUTS

Zhichun Shao
Sedat Pala
Yue Liang
Yande Peng
Liwei Lin
2021

This paper reports a highly directional air-coupled parametric loudspeaker using a single chip of piezoelectric micromachined ultrasonic transducers (pMUTs). Compared with the state-of-art technologies, three distinctive advancements have been achieved: (1) a micromachined parametric array based on CMOS-compatible bimorph AlN pMUTs; (2) generation of highly directional audible sound with a half power beam width less than 5 degrees; and (3) generation of multiple audible frequency using a single chip with 246 pMUT elements in a footprint of 13mm by 13mm. As such, the proposed AlN pMUT...

3D Ultrasonic Object Detections with >1 Meter Range

Zhichun Shao
Yande Peng
Sedat Pala
Yue Liang
Liwei Lin
2021

This paper reports an ultrasonic 3D object detector with > 1 meter range based on an AlN piezoelectric micromachined ultrasonic transducers (pMUTs) chip. Compared with the state-of-art technologies, three distinctive advancements have been achieved: (1) more than 1-meter in sensing distance enabled by a bimorph dual electrode pMUT design; (2) small form factor (6×6 mm2) and a more than 135o field of view; (3) capability of real time 3D object detection with up to 125 fps (frames per second) based on the scheme of ultrasound beamforming. As such, this work could open up a new class of...

Accelerating MEMS Design Process Through Machine Learning from Pizelated Binary Images

Ruiqi Guo
Renxiao Xu
Zekai Wang
Fanping Sui
Liwei Lin
2021

This paper reports the use of machine learning in accelerating the MEMS design process. Candidate designs are represented by pixelated binary 2D images. Instead of common computational tools like FEA, we use trained neural network for quickly obtaining physical properties of interest for each candidate design. Circular disk resonators are used as an example to demonstrate the capability of our method. After sufficient training with 9000 images, the resulting neural network can serve as a high-speed, high accuracy analyzer: it can identify four vibrational modes of interest and calculate...

Rapid Genotypic Antibiotic Susceptibility Test Using CRISPR-Cas12a for Urinary Tract Infection

Juhong Chen
Fuguo Jiang
Chao-Wei Huang
Liwei Lin
2020

The current clinical protocol to conduct a bacterial antibiotic susceptibility test (AST) requires at least 18 hours, and cannot be accomplished during a single visit for patients. Here, a new method based on the technique of CRISPR-Cas12a is utilized to accomplish a bacterial genotypic AST within one hour with good accuracy. Two amplification approaches are employed and compared: (1) enriching the bacterial concentration by culturing in growth media; and (2) amplifying target DNA from raw samples by recombinase polymerase amplification (RPA). The results show that CRISPR combined with RPA...

Finger-Powered Fluidic Actuation and Mixing via MultiJet 3D Printing

Eric Sweet
Rudra Mehta
Yifan Xu
Ryan Jew
Rachel Lin
Liwei Lin
2020

Additive manufacturing, or three-dimensional (3D) printing, has garnered significant interest in recent years towards the fabrication of sub-millimeter scale devices for an ever-widening array of chemical, biological and biomedical applications. Conventional 3D printed fluidic systems, however, still necessitate the use of non-portable, high-powered external off-chip sources of fluidic actuation, such as electro-mechanical pumps and complex pressure-driven controllers, thus limiting their scope towards point-of-need applications. This work proposes entirely 3D printed sources of human-...

3D Microfluidic Concentration Gradient Generator for Combination Antimicrobial Susceptibility Testing

Eric Sweet
Brenda Yang
Joshua Chen
Reed Vickerman
Yujui Lin
Alison Long
Eric Jacobs
Tinglin Wu
Camille Mercier
Ryan Jew
Yash Attal
Siyang Liu
Andrew Chang
Liwei Lin
2020

Microfluidic concentration gradient generators (µ-CGGs) have been utilized to identify optimal drug compositions through antimicrobial susceptibility testing (AST) for the treatment of antimicrobial-resistant (AMR) infections. Conventional µ-CGGs fabricated via photolithography-based micromachining processes, however, are fundamentally limited to two-dimensional fluidic routing, such that only two distinct antimicrobial drugs can be tested at once. This work addresses this limitation by employing Multijet-3D printed microchannel networks capable of fluidic routing in three dimensions to...

High-Aspect-Ratio Three-Dimensional Electrospinning via a Tip Guiding Electrode

Gaofeng Zheng
Jiaxin Jiang
Xiang Wang
Wenwang Li
Zhaojie Yu
Liwei Lin
2021

Electrospinning setup with a sharp tip guiding electrode has been designed for high-aspect-ratio three-dimensional (3D) electrospinning by enhancing the electrical field strength to guide nanofibers toward designated paths layer by layer. This setup helps to deposit nanofibers under a steady charge transfer process and overcomes the electrical interferences. The polymer jet via the electrohydrodynamic process has been used to direct-write ordered, 3D structures with the aspect-ratio (height/width) up to 25 for various patterns, such as rectangular grids and five-point stars....

Electrohydrodynamic 3D Printing of Orderly Carbon/Nickel Composite Network as Supercapacitor Electrodes

Bing Zhang
Jiangkang He
Gaofeng Zheng
Yuanyuan Huang
Chaohung Wang
Peisheng He
Fanping Sui
Lingchua Mueng
Liwei Lin
2021

Electrohydrodynamic (EHD) 3D printing of carbon-based materials in the form of orderly networks can have various applications. In this work, microscale carbon/nickel (C-Ni) composite electrodes with controlled porosity have been utilized in electrochemical energy storage of supercapacitors. Polyacrylonitrile (PAN) was chosen as the basic material for its excellent carbonization performance and EHD printing property. Nickel nitrate (Ni(NO3)2) was incorporated to form Ni nanoparticles which can improve the conductivity and the capacitance performance of the electrode. Well-aligned PAN-Ni(NO3...

A 36-Channel Auto-Calibrated Front-End ASIC for a pMUT-Based Miniaturized 3-D Ultrasound System

Jihee Lee
Kyoung-Rog Lee
Benjamin E. Eovino
Jeong Hoan Park
Luna Yue Liang
Liwei Lin
Hoi-Jun Yoo
Jerald Yoo
2021

We present an area- and power-efficient application-specific integrated circuit (ASIC) for a miniaturized 3-D ultrasound system. The ASIC is designed to transmit pulse and receive echo through a 36-channel 2-D piezoelectric Micromachined Ultrasound Transducer (pMUT) array. The 36-channel ASIC integrates a transmitter (TX), a receiver (RX), and an analog-to-digital converter (ADC) within the 250-μm pitch channel while consuming low-power and supporting calibration to compensate for the process variation of the pMUT. The charge-recycling high-voltage TX (CRHV-TX) in standard CMOS...