New implanted devices can wrap around tissues

Researchers have created electronic devices that become soft when implanted inside the body and can grip 3-D objects, such as large tissues, nerves and blood vessels.
Scientists from The University of Texas at Dallas and the University of Tokyo said the biologically adaptive, flexible transistors might one day help doctors learn more about what is happening inside the body, and stimulate the body for treatments.
The research is one of the first demonstrations of transistors that can change shape and maintain their electronic properties after they are implanted in the body, said Jonathan Reeder, a UT Dallas graduate student in materials science and engineering, and lead author of the work.

"Scientists and physicians have been trying to put electronics in the body for a while now, but one of the problems is that the stiffness of common electronics is not compatible with biological tissue," Reeder said.
"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.
"By putting electronics on shape-changing and softening polymers, we can do just that," Reeder said.

Shape memory polymers developed by Dr Walter Voit, assistant professor of materials science and engineering and mechanical engineering and an author of the paper, are key to enabling the technology.

The polymers respond to the body's environment and become less rigid when they are implanted. In addition to the polymers, the electronic devices are built with layers that include thin, flexible electronic foils first characterised by a group including Reeder in work published last year in the journal Nature.
The Voit and Reeder team from the Advanced Polymer Research Lab in the Erik Jonsson School of Engineering and Computer Science fabricated the devices with an organic semiconductor but used adapted techniques normally applied to create silicon electronics that could reduce the cost of the devices.
The rigid devices become soft when heated. Outside the body, the device is primed for the position it will take inside the body, researchers said.

During testing, researchers used heat to deploy the device around a cylinder as small as 2.25 millimetres in diameter, and implanted the device in rats.
They found that after implantation, the device had morphed with the living tissue while maintaining excellent electronic properties.
The research will be published in the journal Advanced Materials.