flexible electronics

Nanshu Lu's picture

Journal Club Theme of December 2013: Bio-Integrated Flexible and Stretchable Strain Gauges


Strain gauges are widely used across all engineering fields to measure mechanical deformation of a solid object. The most common type of strain gauges consists of a patterned metal foil on a stiff plastic backing sheet glued to the solid object. Deformation in the object leads to deformation in the foil, thereby causing its electrical resistance to change. The fractional change in resistance, ΔR/R0, is related to the mechanical strain by the gauge factor (GF): GF = (ΔR/R0)/ε. The GF for metallic foils are typically between 2 to 5 [1], due mostly to changes in length and cross-sectional area. Compared to metallic foils, semiconductor devices can exhibit much larger GF due to piezoresistive effects [2] where the resistivity changes rapidly with strain due to the dependence of the bandgap on inter-atomic spacing. For example, the gauge factor of p-type [110] single crystalline silicon can be as high as 200 [2]. As a result, for precision measurements, semiconductor gauges, also called piezoresistors, are preferred over metal foils. These types of devices are widely used as ‘hard’ sensors attached to stiff materials such as metals, concretes and high modulus plastics for structural health monitoring or quantifying specimen deformation. 

Nanshu Lu's picture

Call for papers: Soft Robotics - a new journal dedicated to soft machines

Dear colleagues and friends, 


On behalf of the editorial board, I would like to introduce our new Journal, Soft Robotics (SoRo) to the mechanics community. SoRo is an innovative peer-reviewed journal dedicated to the science and engineering of soft materials in mobile machines. The Journal breaks new ground as the first to answer the urgent need for research on robotic technology that can safely interact with living systems and function in complex natural or human-built environments.

Jianliang Xiao's picture

A Conformal, Bio-Interfaced Class of Silicon Electronics for Mapping Cardiac Electrophysiology

In this paper recently feature on the cover of Science Translational Medicine, we report the development of a class of mechanically flexible silicon electronics for multiplexed measurement of signals in an intimate, conformal integrated mode on the dynamic, three-dimensional surfaces of soft tissues in the human body. Mechanics model shows that the strain in the fragile materials, e.g. silicon, is several orders of magnitude smaller than the fracture strain, when wrapped onto the curvilinear cardiac surface.

Teng Li's picture

Symposium on Materials and Devices for Flexible and Stretchable Electronics at 2009 MRS Spring Meeting

Call for papers

2009 MRS Spring Meeting, San Francisco, CA, April 13-17

Symposium PP: Materials and Devices for Flexible and Stretchable Electronics

Abstract Deadline: 3 November 2008


Xue Feng's picture

Theoretical and Experimental Studies of Bending of Inorganic Electronic Materials on Plastic Substrates

In this paper, we report comprehensive experimental and theoretical
studies of bending in structures relevant to inorganic flexible electronics.
Different from previous mechanics models of related systems, our analysis does not
assume the thin film to cover the entire substrate, thereby explicitly
accounting for effects of edges and finite device sizes, both of which play
critically important roles in the mechanics and bending properties. These
thin-film islands give nonuniform stress, with maxima that often appear at the
edges and spatially non-uniform shear and normal stresses along the film/substrate
interface. Although these results are generally applicable to all classes of

Rui Huang's picture

Influence of Interfacial Delamination on Channel Cracking of Brittle Thin Films

H. Mei, Y. Pang, and R. Huang, International Journal of Fracture 148, 331-342 (2007).

Following a previous effort published in MRS Proceedings, we wrote a journal article of the same title, with more numerical results. While the main conclusions stay the same, a few subtle points are noted in this paper.

First, instead of using the approximate formula by Ye, Suo and Evans (1992), we calculate the energy release rate of interfacial delamination emanating from the channel crack exclusively by the finite element method. We found that the approximate formula is not accurate in several cases.

Rui Huang's picture

Fracture, Delamination, and Buckling of Elastic Thin Films on Compliant Substrates

Attached slides were presented at the 2007 ASME Congress at Seattle.

Zhigang Suo's picture

Delamination of stiff islands on stretchable substrates

I attach slides for an ASME talk, which is based on a recent paper.

Nanshu Lu's picture

Co-evolution of local thinning and debonding

Co-evolution of local thinning and debonding

A 1um-thick Cu film was deposited on Kapton 50HN substrate, with a thin Cr interlayer to improve adhesion. The specimen was in-situ annealed at 200oC for 30min after deposition.

This FIB image was taken after the specimen was uniaxially stretched to 50% and released.

Teng Li's picture

Flexible Macroelectronics (a video for middle/high school students)

This is a winning entry in the Sci/Terp Video Competition at University of Maryland (UMD).


jhchen's picture

jianhao chen

Hi, I'm a Physics grad student working with Dr. Ellen Williams. My job is basically making nanoelectronic devices, measuring their characteristics and trying to understand the underlying "Physics".

ENME489X - Introduction (V.Tsai)

What I want to gain from this course is to come to know how flexible macroelectronics are approached and researched. An increasing trend of "thin" applications poses new challenges in terms of low power usage and durability.

Daniel Min's picture

Daniel Min

My name is Daniel Min.  I am a senior mechanical engineering student at the University of Maryland.  I am currently enrolled in Dr. Teng Li's flexible macroelectronics course.  I chose to enrol

James Wang's picture

James Wang

I am Yong Wang, currently a PhD student in the Mechanical Engineering department at the University of Maryland. I got my Bachelor degree from the University of Science and Technology of China and Master degree from the Hong Kong University of Science and Technology. I am enrolled in Dr. Teng Li's class on flexible macroelectronics in this semester.

Kurt Vargas

My name is Kurt Vargas. I am an international student from Costa Rica, currently attending the University of Maryland at College Park. I am a Christian who loves the Lord and serves Him full time. I also love reading my Bible!

adamlr's picture

Adam Rutherford

My name is Adam Rutherford and I am currently a senior mechanical engineering student at the University of Maryland. I am enrolled in Dr. Teng Li's class on flexible macroelectronics. I chose this course out of the selection of electives because I feel that flexible macroelectronics will have a large impact on the consumer electronics industry in the near future.

Josh Crone's picture

Josh Crone

My name is Josh Crone and I am an undergraduate student in Mechanical Engineering at the University of Maryland. I am in the BS/MS program with a focus in mechanics and materials. My current research interests are in atomic force microscopy.

Nathan_Vickey's picture


My name is Nathan and I am a Masters student in my second year at the University of Maryland, College Park studying mechanical engineering.  I was born and raised in Erie, PA.  For my undergraduate studies, I attended the University of Pittsburgh in Pittsburgh, PA where I also studied mechanical engineering.  When I am not engineering, I enjoy running, playing the piano, and following the stock market. 

Dan Forrest's picture

Dan Forrest

My name is Dan Forrest and I am currently a biological resources engineering student at the University of Maryland. I am taking ENME489X: Flexible Macroelectronics to fulfill a degree requirement. However, I chose this specific class because the topic in general seemed interesting to me and appears to be an up and coming field in the electronics industry.

Anand_Pillarisetti's picture

Anand Pillarisetti

My name is Anand Pillarisetti. I am a graduate research assistant at University of Maryland, working towards my doctoral degree in mechanical engineering. I received Master of Science (MS) degree in mechanical engineering and mechanics from Drexel University, Philadelphia, PA and Bachelor of Technology (B-Tech) degree in mechanical engineering from National Institute of Technology (NIT), Warangal, India.  I am currently enrolled in the course "Flexible Macroelectronics" taught by Dr. Teng Li at University of Maryland.

Hongbo Bi's picture

Hongo Bi

My name is Hongbo Bi and I am a Ph.D candidate in Mechanical Engineering under Dr. Bongtae Han at the University of Maryland, College Park. I recieved Master of Science (M.S.) degree in Mechanical Engineering from University of Maryland, College Park and and Bachelor of Engineering (B.E.) in Automatic Control from University of Science and Technology of China. I am currently entrolled into class of Flexible Macroelectronics (ENME808H) at the University of Maryland, which is taught by Prof. Teng Li.

Daniel Kodan's picture

Daniel Kodan

My name is Daniel Kodan, I am an undergraduate Mechanical Engineering student at the University of Maryland.  I am currently taking a flexible macroelectronics class taught by Dr. Teng Li.  I am

Gary Palmer's picture

Gary Palmer II

Hi my name is Gary Palmer II and I'm a senior mechanical engineering major at the University of Maryland. My interest in flexible macroelectronics stems from its future capabilities. The fact that these components can be integrated with everyday objects is fascinating. Since this technology will be used in the future, it will be great to be on the leading edge of its development.

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