Informed by mechanics and computing, flexible bioelectronics can better suit curved bodies

(Nanowerk News) These days, foldable phones are everywhere. Now, using models that predict how well flexible electronics will conform to the surface of a ball, University of Wisconsin–Madison and University of Texas at Austin engineers can usher in a new era in which these flexible devices can integrate seamlessly with parts of the human body. .

In the future, for example, a flexible bioelectronic artificial retina implanted in a person’s eyeball could help restore vision, or a smart contact lens could continuously sense glucose levels in the body.

“With our powerful simulation model, we can now predict suitability immediately, which dramatically speeds up the design process for flexible electronics,” said Ying Li, a professor of mechanical engineering at UW–Madison, whose research group developed the computational model. “The simulation results provide a very clear guide for researchers, who can now determine the optimal design without the need to perform many time-consuming experiments.”

The researchers detail their work in a paper published in the journal Science Advances (“Fitness of flexible sheet on spherical surface”). This is a rendering of an artificial retina using bioelectronics.

To work as expected, bioelectronic devices must make very close contact with living tissue and avoid buckling or creasing. However, researchers have struggled to get flexible electronics to fully conform to the so-called “unexpandable surfaces” – spherical-like surfaces that cannot be flattened without breaking or creasing – that exist throughout the human body.

In this study, the research team used a combination of experimental, analytical, and numerical approaches to systematically investigate how circular polymer sheets (which mimic the mechanical properties of flexible electronics), as well as partially cut circular sheets, orient themselves on a spherical surface. Analyzing those results allows researchers to derive ready-made formulas that reveal the underlying physics and predict the suitability of flexible electronics.

“The results from our three different methods all show similar physics, which is interesting,” said Nanshu Lu, a professor in the Department of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin, who led the experimental research. “We formulate very simple mathematical equations to guide flexible electronic designs to optimal fit, and this will have a significant impact in the field.”

In addition, the researchers demonstrated a simple and elegant method for increasing the ability of flexible sheets to conform to spherical surfaces. Inspired by the Japanese art of kirigami, where paper is cut and folded, the researchers made the simplest possible radial cuts on circular sheets, increasing their fit from 40% to more than 90%.

Li said these advances will drive innovation in the field by enabling other researchers to design better flexible electronics.

“This is the first work that provides a complete picture for understanding the complex processes of how flexible electronics adapt to these complex surfaces,” said Li. “This advancement will pave the way for all future studies in the field of developing bioelectronics that are more suited to the human body.”