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The Building Blocks of Circuits, Now Ready to Wrap Around Your Internal Organs

New transistors are flexible enough to become part of your guts.
Image: the University of Texas at Dallas

Your guts are a wet, warm, and floppy place. There are no hard surfaces—excluding bones, if you consider those to be properly "guts," which they are not—straight lines, or sharp corners. It's a good way of being: resilient. Your guts can take a hit, and they can adapt to all sorts of visitors, like 12 cans of Iron City beer or unprecedented volumes of turkey dinner or, hell, even a new human being. For being bags of slop, we get a lot done.

In this sense, there's a disconnect between humans (and other animals) and machines. Sewing an electronic device into/onto a human body winds up looking like "biohacker" Tim Cannon's skin-embedded vital signs monitor or Neil Harbisson's Eyeborg synesthesia-mimicking monocle. One might even consider the prevailing notion that cybernetic technology should naturally make humans more machine-like rather than the other way around to be pretty silly when you think about it, just given the fact that we're the ones doing the designing.

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A major barrier to implantable electronics is that circuits are typically built on a rigid substrate material, like silicon wafers. Nanomaterials can do "stupid" tasks in the body like signalling, but so far the prospect of a full-on computer has involved the introduction of a material that's very anti-guts. A study released this week in the journal Advanced Materials offers the prospect of transistors, the building blocks of circuits, that can bend and flex enough such that they can wrap around structures within the body, just like the body's internal structures wrap around each other. And, crucially, the transistors only lose their rigidity once they're in the body and heated up; during implantation, they remain stiff, a necessity for surgery.

“You need the device to be stiff at room temperature so the surgeon can implant the device, but soft and flexible enough to wrap around 3-D objects so the body can behave exactly as it would without the device," explains Jonathan Reeder, a University of Texas graduate student and lead author of the study, in a press release. "By putting electronics on shape-changing and softening polymers, we can do just that.”

The key is the utilization of shape memory polymers, materials that can change from a temporary shape back into a permanent one with the application of a particular stimulus, like a temperature change. The semiconductor itself is organic, but the team managed to adapt it to more typical circuit manufacturing processes, paving the way toward deployment of the technology as cheaply as possible. The basic process is to sandwich together the polymer and the transistor, laminating and curing the shape-shifting top layer onto the electronics below.

Reeder et al tested the process on rats, first deploying the material around the surface of a tiny cylinder and then implanting the cylinder. The effect was the material essentially "morphing together" with the rat's living material. The next step is shrinking the material even further, allowing for more components, more complexity, and additional sensing capabilities. That's the immediate goal, after all: sensors in the body that can tell doctors exactly what's going on in there with no need for scalpels and still-limited imaging devices. Beyond that, it's up to your imagination.