Self-powered Multimodal Smart Skin Enabled by Triboelectricity and Hygroelectricity

Principal Investigator: Dr. Dong-Myeong Shin (Assistant Professor, Department of Mechanical Engineering)

This project is showcased as the Research Highlight (November – December 2023) in the third exhibition – Technology for Future in Innovation Wing Two

Project information


Tactile e-skins mimicking functions of human skin can sense tactile modalities such as pressure, vibration, temperature, and humidity. They are essential components for smart robotics, health monitoring devices and human–machine interfaces. However, complicated materials, sophisticated manufacturing, device integration and external power sources are required for most of existing multi-functional e-skins, which severely limit their widespread use.
Self-powered skin capable of sensing pressure, vibration and humidity.

Main Features of the Invention

  • Aluminum / Single-ion conducting electrolyte / gold enabled triboelectric and hygroelectric sensing
  • Simultaneous sensations of pressure, vibration and humidity
  • Easy fabrication and compact size (thickness < 3mm)
  • High sensitivity (limit of detection: 1.04 kPa) and fast response (5.1 ms)
  • Self-powering (305 nW by triboelectricity and 25 nW by hygroelectricity)
  • As high as 84.0%-100.0% signal interpretation accuracy assisted by machine learning algorithm
The photographs of the 5×5 sensory array
Triboelectric and hygroelectric working principle
The pressure sensitivity of hygroelectric output voltages
Statistics of the stimuli and sensation interpreted by machine learning

Achievement of the Project

  • X. Ma, E. Kim, J. Zhou, J. Gao, C. Kim, X. Huan, J. T. Kim, D-M. Shin*, “Self-powered smart skins for multimodal tactile perception based on triboelectric and hygroelectric working principles”, Nano Energy 2023, 113, 108589.
  • A US patent of this invention has been filed in 03/22/2023. Application Number: 63453817.

About the Scholar

Dr. Dong-Myeong Shin is currently Assistant Professor of Mechanical Engineering at the University of Hong Kong (HKU). He was inspired to work in nanoscience as an undergraduate researcher at Pusan National University (BS, 2009), where his work focused on the bioprotection effect of sugar glass on the living cell. He obtained his M.S (2011) and Ph.D. (2016) degrees in nanomaterials at PNU. Dr. Shin’s research interests include Flexible and stretchable energy harvesting/storage devices and bioinspired sensors operational in the range of micro-milli Watt.


Dr. Dong-Myeong Shin
Article of this work

Title: Self-powered smart skins for multimodal tactile perception based on triboelectric and hygroelectric working principles 

Abstract: Human being perceives multiple tactile modalities in the process of sensation on the skin and interpretation in the brain. To date, several sensing techniques facilitate the accurate measurement of individual tactile modality, but multimodal static and dynamic sensing remain challenging. Moreover, low-cost and highly efficient interpretation techniques are still required for tactile perception. Herein, we present cost-effective and high-performing self-powered smart skins that mimic multimodal tactile perception, enabling accurate perception of pressure, vibration, and humidity in the process of sensation on the smart skin and interpretation by machine learning. The dynamic and static stimuli are encoded by triboelectric and hygroelectric principles in the smart skins, respectively, while the hygroscopic nature empowers humidity sensation capability in the smart skin with an accuracy rate as high as 84.0%− 100.0%. We believe our smart skin will enable the smooth transition of e-skin into practical applications, such as robotics, prosthetics, healthcare, and intelligent industry.

Press release

HKU Mechanical Engineering researchers develop ultra-strong aerogels with materials used in bullet-proof vests

The press release article can be founded in HKU Press release (

Aerogels are lightweight materials with extensive microscale pores, which could be used in thermal insulation, energy devices, aerospace structures, as well as emerging technologies of flexible electronics. However, traditional aerogels based on ceramics tend to be brittle, which limits their performance in load-bearing structures. Due to restrictions posed by their building blocks, recently developed classes of polymeric aerogels can only achieve high mechanical strength by sacrificing their structural porosity or lightweight characteristics.

A research team led by Dr Lizhi Xu and Dr Yuan Lin from the Department of Mechanical Engineering of the Faculty of Engineering of the University of Hong Kong (HKU), has developed a new type of polymer aerogel materials with vast applicational values for diverse functional devices.

In this study, a new type of aerogels was successfully created using a self-assembled nanofiber network involving aramids, or Kevlar, a polymer material used in bullet-proof vests and helmets. Instead of using millimetre-scale Kevlar fibres, the research team used a solution-processing method to disperse the aramids into nanoscale fibrils. The interactions between the nanofibers and polyvinyl alcohol, another soft and “gluey” polymer, generated a 3D fibrillar network with high nodal connectivity and strong bonding between the nanofibers. “It’s like a microscopic 3D truss network, and we managed to weld the trusses firmly together, resulting in a very strong and tough material that can withstand extensive mechanical loads, outperforming other aerogel materials,” said Dr Xu.

The team has also used theoretical simulations to explain the outstanding mechanical performance of the developed aerogels. “We constructed a variety of 3D network models in computer, which captured the essential characteristics of nanofibrillar aerogels,” said Dr Lin, who led the theoretical simulations of the research. “The nodal mechanics of fibrillar networks are essential to their overall mechanical behaviours. Our simulations revealed that the nodal connectivity and the bonding strength between the fibres influenced the mechanical strength of the network by many orders of magnitudes even with the same solid content,” said Dr Lin.

“The results are very exciting. We not only developed a new type of polymer aerogels with excellent mechanical properties but also provided insights for the design of various nanofibrous materials,” said Dr Xu, adding, “the simple fabrication processes for these aerogels also allow them to be used in various functional devices, such as wearable electronics, thermal stealth, filtration membranes, and other systems,”

The research was published in Nature Communications, in an article entitled “Ultrastrong and multifunctional aerogels with hyperconnective network of composite polymeric nanofibers”.

Link of the paper:

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