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The Laser's Edge of Soft Robotics

Across the world, engineers studying soft robotics are developing a whole new generation of ideas for artificial muscles, wireless implants or even controlling satellite mechanisms in space. The materials respond to the power of heat, air, fluids, light, magnetic fields or electricity in different ways. They can perform different functions using relatively low energy, and don’t wear down as easily.

The missing piece to the puzzle, however, is creating them in the most efficient way. The Ohio State University has an answer. 

Electrical and Computer Engineering Assistant Professor Liang Guo designs soft electronic materials to perform different functions – based simply on how they are cut by lasers.  

The research, featured on the December cover of Advanced Engineering Materials magazine, allows for precise control of various squeezing, gripping, flapping and lifting actions to benefit technologies in a variety of smart devices, such as solar tracking systems, batteries, 3D mesostructures, energy harvesting and biomedical devices. 

Guo’s team member, Ohio State Graduate Research Associate, Bingxi Yan, is creating electroactive conducting polymer films for implantable soft robotics. They are working alongside Chunping Ma and Nan Hu of Ohio State Civil, Environmental and Geodetic Engineering. Together, they released the research, “Geometrically Enabled Soft Electroactuators via Laser Cutting.” 

Guo said the engineering problem to date is that current soft robotics technology requires too many hinges, adhesives or coatings, in order to fulfill a specific function. Despite a rapidly expanding library of electroactive materials, he said precise and repeatable structuring remains a challenge – until now. 

According to their proposal, the technology “has sparked diverse biomedical devices, including dynamic catheters, diaphragms, and wirelessly powered insulin pumps… through rational picks and combinations, this cutting approach may offer an unprecedented route.”

“We have produced a patterning program to create functionized materials for different actions depending upon how they are cut,” Yan said.

From left, Liang Guo and Bingxi Yan In Dreese Labs.At Dreese Laboratories, Guo and Yan explain on a white board how it works. They start with a soft polyethylene terephthalate film, pre-coated with titanium and gold. Another layer deposits the conducting polymer, polypyrrole, which reacts to an applied voltage. 

Much like cutting paper into spirals produces springing coil designs, radial cuts and other transverse cuts can produce even more options. Layering them together opens the door for greater precision. 

Guo said cuts are made in the material through a laser-patterning process for accuracy and durability. The soft material is activated by consistently switching low voltages, bringing a current that gradually declines between each pulse or function. 

“These patterns are selected and fine-tuned… into appealing modes for various potential functions,” their research states. “The integrity of such geometrically enabled electroactuators not only improves reproducibility and predictability of their ultimate performance but also avoids laborious assembling and mechanical failures.” 

More importantly, the same low-cost material can then perform different functions for even greater efficiency.

Guo said their specific goal is to develop wireless implants inside the body to deliver insulin doses for diabetic patients, which requires a squeezing function to control the fluid flow. Their soft electroactuator design allows for more precise and repeatable control of such an artificial muscle. 

Advanced Engineering Materials is the premier journal for all the latest breakthroughs in engineering materials and novel materials that are making those important first steps towards commercialization, with a strong focus on new manufacturing techniques.