Researchers at the University of Texas, Dallas and the University of Tokyo have demonstrated ways to print transistors on plastic substrates that then can conform to structures in the body such as blood vessels, nerves, or tendons. This will make it possible to create devices that can monitor or deliver therapeutic treatments to specific locations within a patient’s body.
The key to this approach is the use of shape-memory polymers (SMPs). These plastics have the useful characteristic of holding different shapes at different temperatures. In this case, the material takes the form of a flat plate at room temperature, but when it softens at body temperature, it can take on a different form such as a helix with a predetermined diameter. The chemical composition of the material can be adjusted to tune the “glass transition temperature” where the transformation occurs.
This means that the electronics can be printed on the SMP layer as a rigid substrate. (The researchers have also demonstrated printing the semiconductor devices on a separate substrate and then transferring them to the SMP layer. The resulting device is then sealed with an encapsulating layer. When the device is inserted in a body, it warms up and takes on its predetermined shape. Here is a video that demonstrates how such a device can automatically wrap itself around a cylindrical structure as it warms up:
This work was reported in an article, “Mechanically Adaptive Organic Transistors for Implantable Electronics,” published online in April 2014 by the journal Advanced Materials.