Electronics
The silicon wafers that serve as the substrate for microelectronic devices are too flat and rigid to conform to surfaces of the human body.
to minimise the removal of the material, or how to maximise the coverage of the device on the spherical surface,” she says. “Therefore, we have to compromise on the number of pixels and the field of view.” When talking about restoring a person’s sight with what could potentially be a better technology than the currently available retinal implants, which produce blurred or distorted images due to their inability to conform to the eye, those sacrifices aren’t really an option. Luckily, Li and his colleagues at the University of Wisconsin- Madison had been building a software package to simulate flexible structures with highly complex geometries and loading conditions, and he was able to apply it to Lu’s problem. “The basic idea is actually pretty simple,” says Li. “We discretise the flexible electronics into a lattice spring network structure to make the simulation much easier and more efficient to handle.” With the modelling software, Li simulated the conformability of circular polymer sheets – which mimic the mechanical properties of flexible electronics – both fully intact and with strategically placed slits, to a plastic hemisphere. Using the same components, the researchers made slits into the polymer sheet according to the parameters for best practice given by the software. The result was an improvement in conformability from 40% to more than 90%. Analysing those results enabled the researchers to derive a ready- to-use formula that reveals the underlying physics and predicts the conformability of flexible electronics. “It’s like a digital twin technology,” says Li. “We can build a variety of different models, run the simulation and get the solution.” This process, he adds, can take a matter of minutes or hours depending on the number of models and their complexity.
Considering the hours that go into experimentation with medical devices to reach a workable prototype, it’s not difficult to imagine the benefit that a
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computational model could bring to the field. This is especially true given the flexibility of the software. “We’re using mathematics and computational tools to provide a very generic guideline for the theoretical study of this kind of challenge,” says Lu. She adds that the mathematical equations within her and Li’s research provide a framework for others to conduct similar experiments by changing the values according to attributes like the radius and thickness of the materials they’re working with. “Our equations can readily give them how many cuts and how long the cuts should be,” she says. These equations are specific to spherical surfaces, but using the software package, “any arbitrary surface can be numerically simulated”, Lu adds.
Part of the significance Lu sees in her and Li’s research is that it could shift the nature of expertise required to design flexible electronics with medical applications. In a field that tends to be dominated by the electrical engineers who design the circuits and mechanical engineers focused on manufacturing them, as well as materials scientists and chemical engineers, she sees the approach she and Li have taken to solve their artificial retina problem as both an outlier and a catalyst. “Our work is the starting point for this line of research,” says Lu. “We need to continue to educate the major players in this field so that they can understand the value of this kind of fundamental research and how they can leverage it without knowing the complicated mathematics and mechanics.” Just how fundamental the duo’s simulation-based approach will be to the future of flexible electronics remains to be seen, but researchers grappling with similar problems have nothing to lose by trying it out. “The package is already open-source through a GitHub repository,” says Li. “The current name is OpenFSI.” ●
Medical Device Developments /
www.nsmedicaldevices.com
IM Imagery/
shutterstock.com
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