Moving implant, body nets advance
Stanford researchers described two methods for using magnetic fields to propel a millimeter-sized device through fluid at half a centimeter per second. They aim to open up a wide array of new medical applications for tiny remote-controlled implants.
A senior engineer from Toumaz Ltd., described a prototype transceiver that integrates 802.15.6 and Bluetooth Low Energy radios to enable body area networks (BANs). Separately, researchers described a BAN chip that could harvest up to 100 microwatts from the temperature of the human body.
Stanford PhD student Anatoly Yakovlev tapped into the vision of the 1966 movie “Fantastic Voyage,” describing two methods for moving a 0.6mm2 chip wirelessly through a fluid. The techniques assumed a patient would lie on a magnetized bed generating a 0.1 Tesla field while a care provider used a 2 W transmitter to control forward motion of a 3×4 millimeter implant.
Yakovlev showed videos of both methods. Researchers showed Stanford medical center physicians who specialize in cardiovascular ablation surgeries a version of the device used to guide a wired catheter.
The current device can only generate forward motion and is too large for use in animal tests. “Looking ahead hopefully sub-millimeter devices are possible, and there are some challenges to solve, but at this stage we just want to demo propulsion,” said Yakovlev.
Medical electronics companies will want a new and smaller prototype suitable for animal testing before they engage with the technology, he said. In parallel, Yakovlev and colleagues hope to design a version with bi-directional links to better monitor and control motion of the device.
The paper and earlier ones on the technology were co-authored with Stanford professor Teresa Meng, a wireless pioneer who co-found Wi-Fi vendor Atheros. Researchers believe the techniques could be used for more precise drug delivery, diagnostics and microsurgery.
Alan Wong, head of IC design for Toumaz, described an 130 nm transceiver that implemented both IEEE 802.15.6 and Bluetooth Low Energy (BLE) radios for a wireless body area network (BAN).
The chip consumed less than 10 milliwatts in receive or transmit modes. The device was one of the first to implement the 802.15.6 standard expected to be formally ratified as a standard in the next few weeks.
Toumaz is about to launch a commercial BAN patch based on its own proprietary low power network using a chip designed three years ago. Following extensive field trials, it got U.S. regulatory approval for the disposable patch late last year.
The new chip is a prototype aimed at demonstrating to medical OEMs and hospitals the potential of standards-based BANs. Wong said consumer devices are expected to adopt BLE or Zigbee while hospitals are more likely to use 802.15.6, in part because it supports data streaming.
The networks could automate tracking of a wide variety of sensors used to monitor patients. “The technology still needs to be proven in commercial use, so we think the first year of sales will be quite slow, but this saves hospitals money and nursing resources,” said Wong.
Texas Instruments and Zarlink are among the other chip makers expected to pursue the opportunity for large medical OEMs such as GE and Philips.
Separately, researchers from the universities of Washington and Virginia showed a wireless sensor node using the 400 MHz medical band that could harvest up to 100 microwatts from human body temperature.
The device included an analog-front end and signal processing blocks to handle ECG, EEG and EMG signals. The 130 nm chip measured 2.5 x 3.3 mm, ran at levels down to 0.3 V and consumed just 19 microwatts thanks to ultra low power blocks throughout the design.