Adrian Perez Tries to Replicate Researchers' Soft Sensor — But Settles for a More Rigid Alternative

Maker and YouTuber Adrian Perez has built a skin-like sensor for soft robotics, using magnetic tape layered with silicone and a Hall effect sensor — implementing a design detailed in a 2019 scientific paper by researchers at Tarbiat Modares University.

"I want my robots to be able to touch things, but more importantly feel things," Perez explains. "No, not love, just pressure. I engineered this robotic skin so I could detect the force that my robots are feeling. My goal is to make a cheap skin that I can apply to any surface — I could have done something simple like just buy a sensor online, but I wanted to make my own really cheap skin sensor."

Perez' project, dubbed Iroh, stands on the shoulders of giants: his approach is based on that of Tarbiat Modares University researchers Hossein Mirzanejad and Mahdi Agheli, as detailed in their 2019 paper in Sensors and Actuators A: Physical. "[We designed] a new soft Hall based sensor," the pair explained at the time, "by replacing the neodymium magnet with the magnetic powder blended with silicone rubber. In addition to eliminating extra components and providing a totally soft structure, this solution allows the user to fabricate and utilize the sensor in lower thicknesses due to weaker magnetic field of the powder."

Iroh uses the same design: a commercial Hall effect sensor sits under a layer of silicone rubber, above which is a second layer of "magnetic skin" — made from a mixture of magnetized iron filings and silicone, as a lower-cost and more approachable alternative to the specialized magnet powder used in Mirzanejad and Agheli's original prototype. Sadly, what appeared at first glance to be a cheap alternative proved unsuitable — Perez having been misled by OpenAI's large language model ChatGPT, which is neither a search engine nor a knowledge base yet is often treated as both, into thinking the pure iron filings would retain magnetism long enough for the process to work.

Perez' final solution is a twist on the original design, and loses some — but not all — of the desired flexibility: the upper layer, originally designed to be a mixture of silicone and magnet powder, is replaced by commercial self-adhesive magnetic tape. "It's still flexible," Perez says. "It's not as flexible as I would like it to be, but it's flexible."

The project is documented in full on Perez' YouTube channel, and in the video embedded above.