Liwei Lin (Advisor)

Research Advised by Professor Liwei Lin

BSAC Co-Director, Professor Liwei Lin Named 2022 Bakar Fellows Spark Award Recipient

August 1, 2022

Liwei Lin, Bakar Fellow Spark Award Recipient 2022

The Bakar Fellows Spark Award is designed to accelerate Berkeley faculty-led research to tangible, positive societal impact through commercialization. Through a competitive application process, faculty members are selected as Bakar Faculty Fellows and awarded discretionary research support to fulfill proposed milestones and move their innovative...

Neil Ramirez

Graduate Student Researcher
Mechanical Engineering
Professor Liwei Lin (Advisor)
Ph.D. 2022

Neil received his B.S. in Mechanical Engineering from the Ohio State University in 2017 and M.S. from Berkeley in Spring 2019. He is currently a 4th year PhD candidate in the Liwei Lin group. His research focuses on flexible devices for applications in energy generation and sensing.

A High Seebeck Coeffiecient Thermoelectric Generator Based on a Self-Healing Ionogel

Yu Long
Peisheng He
Yande Peng
Liwei Lin
2022

In this work, we report a thermoelectric energy harvester based on an ion-conductive ionogel withthree distinctive features as compared with the state-of-art systems: (1) selfhealable in both thematerial and device operations under large deformations; (2) ultrahigh Seebeck coefficient withthe measured value of 7068 μV/K for the material, and 298 μV/K for a prototype energy harvesterin operations; and (3) stable performances under large bending states with little...

Facile Fabrication of Multilayer Stretchable Electronics via a Two-Mode Mechanical Cutting Process

Renxiao Xu
Peisheng He
Guangchen Lan
Kamyar Behrouzi
Yande Peng
Dongkai Wang
Tao Jiang
Ashley Lee
Yu Long
Liwei Lin
2021
A time- and cost-effective fabrication methodology via a two-mode mechanical cutting process for multilayer stretchable electronics has been developed without using the conventional photolithography-based processes. A commercially available vinyl cutter is used for defining complex patterns on designated material layers by adjusting the applied force and the depth of the cutting blade. Two distinct modes of mechanical cutting can be achieved and employed to establish the basic fabrication procedures for common features in stretchable electronics, such as the metal interconnects, contact...

Programmable Tactile Feedback Patterns for Cognitive Assistance by Flexible Electret Actuators

Tao Jiang
Wenying Qiu
Zhaoyang Li
Xing Ye
Yuhan Liu
Yushi Li
Xiaohao Wang
Junwen Zhong
Xiang Qian
Liwei Lin
2021

Advanced tactile feedback systems are important tools in the field of human–machine interfaces. In this work, an airflow-assisted corona charging process is utilized to charge films made of electret material for the construction of a sandwich-structured flexible actuator system. With a voltage as low as 20 V, this flexible actuator can stimulate skin sensations for basic tactile feedback functions. Under a driving voltage of 200 V, the system can generate an output force of ≈55 mN, which is larger than that of the output force by cellphones under the vibration mode. Utilizing these...

Gold NanoParticle Based Plasmonic Sensing for the Detection of SARS-CoV-2 Nucleocapsid Proteins

Kamyar Behrouzi
Liwei Lin
2022

An inexpensive virus detection scheme with high sensitivity and specificity is desirable for broad applications such as the COVID-19 virus. In this article, we introduce the localized surface plasmon resonance (LSPR) principle on the aggregation of antigen-coated...

Deep Learning for Non-Parameterized MEMS Structural Design

Ruiqi Guo
Fanping Sui
Wei Yue
Sedat Pala
Kunying Li
Renxiao Xu
Liwei Lin
2022

The geometric designs of MEMS devices can profoundly impact their physical properties and eventual performances. However, it is challenging for researchers to rationally consider a large number of possible designs, as it would be very time- and resource-consuming to study all these cases using numerical simulation. In this paper, we report the use of deep learning techniques to accelerate the MEMS design cycle by quickly and accurately predicting the physical properties of numerous design candidates with vastly different geometric features. Design candidates are represented in a...

Mapping and Simultaneous Detection of Arterial and Venous Pulses using Large-Scale High-Density Flexible Piezoelectret Sensor Array

Liuyang Han
Wei Zeng
Ying Dong
Xiaohao Wang
Liwei Lin
2022

Flexible sensors with the capability of mapping and examining real-time physiological signals are essential in smart health monitoring systems. Here, high-density and large-scale flexible pressure sensor arrays with the piezoelectric-like dynamic output effects are presented for the mapping and detection of arterial and venous pulses simultaneously. A high equivalent d33 value of 5400 pC N-1 is characterized based on the crisscross groove structure of a single sensor unit with a high dynamic sensitivity of 15.22 nA kPa-...

An Improved Lumped Element Model for Circular-Shape pMUTs

Sedat Pala
Liwei Lin
2022

This paper presents an improved lumped element model for clamped, circular-shape, piezoelectric micromachined ultrasonic transducers (pMUTs). A small signal equivalent circuit is developed to include electrical, mechanical, and acoustic domains, which are analyzed separately and combined with the associated couplings. For the first time, a two-term mode shape approach is adapted to reveal intrinsic and extrinsic properties of a pMUT, such as equivalent circuit parameters, input impedance, velocity, displacement, bandwidth, quality factor, directivity, and the on-axis pressure in the...

A Moisture-Resistant Soft Actuator with Low Driving Voltages for Haptic Stimulations in Virtual Games

Wenying Qiu
Zhaoyang Li
Guocheng Wang
Yande Peng
Min Zhang
Xiaohao Wang
Junwen Zhong
Liwei Lin
2022

Strong and robust stimulations to human skins with low driving voltages under high moisture working conditions are desirable for wearable haptic feedback applications. Here, a soft actuator based on the “air bubble” electret structure is developed to work in high-moisture environments and produce haptic sensations to human skin with low driving voltages. Experimentally, the water soaking and drying process has been conducted repeatedly for the first time and the 20th time to test the antimoisture ability of the actuator as it recovers its output force up 90 and 65% of the initial...