In a nondescript laboratory tucked away on the fourth floor of Portland State University (PSU)'s Maseeh College of Engineering and Computer Science, a peculiar dance is taking place. Artificial muscles, made from braided, inflatable mesh tubes, contract and relax in a rhythmic pattern. These aren't your average robotic components; they're part of a cutting-edge collaboration involving Maseeh College's Agile and Adaptive Robotics Lab (AARL), led by Alex Hunt and Liquid Wire, a local startup pushing the boundaries of flexible electronics.

Hunt, a Hinckley Professor in the Mechanical and Materials Engineering Department, has dedicated his career to building models of how animals control their bodies in the world. His latest project, however, required a partner to provide a missing piece of the puzzle. "We were using different sensors before," Hunt explains, "but they were very difficult to work with, noisy and imprecise."

Enter Liquid Wire, a company founded by PSU alumnus Mark Ronay with the research and development arm helmed by Mike Hopkins, a PSU PhD graduate in applied physics. Liquid Wire emerged from The PSU Center for Entrepreneurship, a hub for fostering innovation and entrepreneurship across the university, providing access to resources such as mentorship, funding, and connections to the broader business community. Since 2018, this center has facilitated the launch of approximately 40 student-initiated companies. Liquid Wire participated in the 2016 Cleantech Challenge and Invent Oregon in 2018, successfully raised $25 million in both public and private investment, and has grown to employ 40 people.

Liquid Wire specializes in stretchable interconnections and advanced strain-sensing technology, exactly what Hunt's lab needed. "Our conductive material is more of a gel," Hopkins describes, demonstrating a silvery substance that holds its shape yet flows like a liquid. "It follows the motion of whatever material it is applied to. If the material comes back to the same spot, you're going to electrically read the same signal."

This unique property made Liquid Wire's sensors ideal for Hunt's artificial muscles, known as Braided Pneumatic Actuators (BPAs). These BPAs, which contract when inflated with air, form the basis of Hunt's biomimetic robots. The challenge was finding a way to accurately measure their movement, akin to the stretch receptors in animal muscles.

Rochelle Jubert, who graduated this past spring from Maseeh College with a BS in Mechanical Engineering, worked on the project as an undergraduate. In the Agile and Adaptive Robotics Lab, "we focus on using bio-inspired robots to study artificial neural networks specifically for proprioception, our ability to sense our bodies in space," she explained.

Jubert's role bridged the gap between Liquid Wire's technology and Hunt's robotics. "I had to figure out how to attach the sensors to the artificial muscles and then calibrate the signal," she recalls. Her solution? A flexible nylon sleeve sewn onto the BPAs, with Liquid Wire's sensors attached across the muscle. For Jubert, now working at Portland-based Biomotum on powered exoskeletons for individuals with mobility impairments, the experience was transformative. "I learned to be an intuitive engineer and learned to communicate," she reflects. "This project taught me how to be an engineer."

The research collaboration has yielded promising results, culminating in a paper presented at the Living Machines conference in Chicago. But for Hopkins, the implications stretch far beyond academia. "You're definitely going to find these in medical devices, pressure sensing, and breath monitoring," he predicts. "A number of pressure sensor applications in wearables where you really want to hide your electronics within the textile."

As for the future, Hunt sees potential for scaling up the research, hinting at plans to measure multiple muscles simultaneously. Meanwhile, Hopkins is focused on the industry-wide impact. "There are a rift of standards coming through," he notes. "I think that's going to be a very big shift... it's going to speed the go-to-market for all of these companies."

In the AARL, the artificial muscles continue their contractions while the sensors track their movements, a testament to the power of collaboration between academia and industry. In this small corner of the Pacific Northwest, the future of flexible electronics and biomimetic robotics stretches to new limits.

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