SAN FRANCISCO, Calif. Researchers described at the International Solid State Circuits Conference (ISSCC) two implantable wireless chips that could advance medical research on multiple fronts.
One researcher created an implantable blood pressure sensor weighing just 130 milligrams that could send data and absorb power wirelessly. It was targeted for lab rats used to study the impact of genetics on a variety of diseases and treatments.
"Currently in genetic studies with mice, researchers implant wired vital sign monitors that weigh two grams, 15 percent of the animal's whole body mass," said Peng Cong, a researcher at Case Western Reserve who presented the paper. "These monitors not only induce trauma, but they create signal distortion as well, so results are not reliable," he added.
But cutting the size and weight of the implant ten-fold, the new device opens the door to more reliable research. It is based on a MEMS capacitive pressure sensor mounted on tiny wireless CMOS chip, linked to an inductive power coil.
With the device, researchers can read blood pressure data via an antenna mounted on top of the rat's cage and deliver power to the implant through a coil underneath the cage. It receives power at a 4 MHz frequency and transmits data at up to 48 Kbits/s over a 433 MHz link.
The sensor consumes 300 microwatts, and a future version will need even less power. Ultimately the sensor could include monitors for multiple vital signs, Cong said.
Another Case Western researcher created a wireless chip for brain implants. It could act as a building block in future deep brain simulators used to treat disorders ranging from Parkinson's disease to depression.
The chip can monitor the presence of dopamine, a key neurotransmitter, using a combination of the electrical and chemical signaling techniques actually employed by nerve cells. It integrates four recording channels in a 1.8 x 2.8 mm chip that consumes 1.1 milliwatts and is made in a 0.5-micron CMOS process.
Masoud Roham, a doctoral candidate at Case Western who presented the paper, said the device was the first to tackle both chemical and electrical sensing of neural signals and report the results working in a live animal. The project is part of a broader collaboration with researchers at the Mayo Clinic.
"We envision using this in smart closed-loop deep brain simulators that could automate real-time adjustments of dopamine in patients," he said. It could also be used to report on the effectiveness of certain drug treatments, he added.
Both papers were praised by audience members including Tim Denison, a senior principal design engineer in the neural division of Medtronic, a moderator of the session. "It's an interesting paper," said Denison whose group works on deep brain stimulators.