One problem with embedded sensors for health and medical applications is getting power to the devices. Physical wires brought to the skin can be difficult to embed and pose a risk as an entry point for infection. Wireless power transfer is one possibility, but some methods such as radio frequency (RF) transmissions could pose a problem by damaging sensitive tissues. Researchers at Stanford University may have developed an attractive alternative approach using ultrasound.
Ultrasound has long been a standard means of creating images inside the human body, including fetuses during pregnancy, and is widely accepted as safe for human tissues. The new approach uses ultrasound to beam energy to a tiny chip that can convert it to electricity that can then power a sensor and a transmitter to relay the resulting data to a controller.
The chip uses a piezoelectric material that absorbs the sound waves and converts the motion caused by them into electricity. The team has already demonstrated a prototype the size of a ballpoint pen tip at the IEEE Custom Integrated Circuits Conference in San Jose. Their plan is to create a device that is just one-tenth that size. This could lead to networks of embedded microsensors that could provide detailed information about the operation of complex systems, including the brain.