Material Moves Foldable Electronics, New Implantable Medical Devices a Step Closer
September 22, 2015 | University of HoustonEstimated reading time: 3 minutes
Researchers have discovered a new stretchable, transparent conductor that can be folded or stretched and released, resulting in a large curvature or a significant strain, at least 10,000 times without showing signs of fatigue.
This is a crucial step in creating a new generation of foldable electronics - think a flat-screen television that can be rolled up for easy portability - and implantable medical devices. The work, published Monday in the Proceedings of the National Academy of Sciences, pairs gold nanomesh with a stretchable substrate made with polydimethylsiloxane, or PDMS.
The substrate is stretched before the gold nanomesh is placed on it - a process known as "prestretching" - and the material showed no sign of fatigue when cyclically stretched to a strain of more than 50 percent.
The gold nanomesh also proved conducive to cell growth, indicating it is a good material for implantable medical devices.
Fatigue is a common problem for researchers trying to develop a flexible, transparent conductor, making many materials that have good electrical conductivity, flexibility and transparency - all three are needed for foldable electronics - wear out too quickly to be practical, said Zhifeng Ren, a physicist at the University of Houston and principal investigator at the Texas Center for Superconductivity, who was the lead author for the paper.
The new material, produced by grain boundary lithography, solves that problem, he said.
In addition to Ren, other researchers on the project included Chuan Fei Guo and Ching-Wu "Paul" Chu, both from UH; Zhigang Suo, Qihan Liu and Yecheng Wang, all from Harvard University, and Guohui Wang and Zhengzheng Shi, both from the Houston Methodist Research Institute.
In materials science, "fatigue" is used to describe the structural damage to a material caused by repeated movement or pressure, known as "strain cycling." Bend a material enough times, and it becomes damaged or breaks. That means the materials aren't durable enough for consumer electronics or biomedical devices.
"Metallic materials often exhibit high cycle fatigue, and fatigue has been a deadly disease for metals," the researchers wrote.
"We weaken the constraint of the substrate by making the interface between the Au (gold) nanomesh and PDMS slippery, and expect the Au nanomesh to achieve superstretchability and high fatigue resistance," they wrote in the paper. "Free of fatigue here means that both the structure and the resistance do not change or have little change after many strain cycles."
As a result, they reported, "the Au nanomesh does not exhibit strain fatigue when it is stretched to 50 percent for 10,000 cycles."
Many applications require a less dramatic stretch - and many materials break with far less stretching - so the combination of a sufficiently large range for stretching and the ability to avoid fatigue over thousands of cycles indicates a material that would remain productive over a long period of time, Ren said.
The grain boundary lithography involved a bilayer lift-off metallization process, which included an indium oxide mask layer and a silicon oxide sacrificial layer and offers good control over the dimensions of the mesh structure.
The researchers used mouse embryonic fibroblast cells to determine biocompatibility; that, along with the fact that the stretchability of gold nanomesh on a slippery substrate resembles the bioenvironment of tissue or organ surfaces, suggest the nanomesh "might be implanted in the body as a pacemaker electrode, a connection to nerve endings or the central nervous system, a beating heart, and so on," they wrote.
Ren's lab reported the mechanics of making a new transparent and stretchable electric material, using gold nanomesh, in a paper published in Nature Communications in January 2014.
This work expands on that, producing the material in a different way to allow it to remain fatigue-free through thousands of cycles.
Suggested Items
Groundbreaking Ceremony Marks the Beginning of a New Era for Newccess Industrial; The Construction of the MINGXIN Building
04/12/2024 | Newccess IndustrialOn a clear and sunny day in March, the groundbreaking ceremony for the MINGXIN Building took place in Shenzhen, China. This moment marked the official commencement of construction for a project that will reshape the semiconductor materials industry.
The Need for a Holistic Global Sustainability Standard
04/10/2024 | Michael Ford, Aegis SoftwareNo one can deny that the resources of our fragile planet are finite. The environment seems like a third party, subject to constant degradation. We’re acutely aware of the effects of pollution on our climate, and despite our “throw-away” culture, recycling and recovery of materials has remained relatively expensive, even as we use more energy just to survive.
iNEMI Publishes Four Roadmap Topics
04/04/2024 | iNEMIThe International Electronics Manufacturing Initiative (iNEMI) announces the availability of the first roadmap topics in the new iNEMI Roadmap format. Printed circuit boards, sustainable electronics, smart manufacturing, and mmWave materials and test are now available online.
Insulectro’s 'Storekeepers' Extend Their Welcome to Technology Village at IPC APEX EXPO
04/03/2024 | InsulectroInsulectro, the largest distributor of materials for use in the manufacture of PCBs and printed electronics, welcomes attendees to its TECHNOLOGY VILLAGE during this year’s IPC APEX EXPO at the Anaheim Convention Center, April 9-11, 2024.
Checking In With ICAPE Group
04/03/2024 | Nolan Johnson, I-Connect007ICAPE Group’s field application engineer Erik Pederson drills down on sustainability, supply chain resiliency, and what value engineering really looks like in this exclusive interview. Founded in 1999, European-based ICAPE Group provides 21 million printed circuit boards and over six million technical parts to manufacturers every month. With 30 PCB manufacturing partners globally and 50 partners providing a wide array of technical parts, ICAPE Group has operations in China, Taiwan, Thailand, South Korea, Vietnam, South Africa, Europe, Mexico, and the United States. The company also focuses on the value proposition for its customers.