We've already seen wirelessly powered implants that stimulate muscles or neurons when activated by an external transmitter. Taking things a step further, scientists are now able to activate multiple implants sequentially, still using just one transmitting device.
First of all, why would anyone want to trigger two or more implants in rapid succession, one after the other? Well, such a system could conceivably be used to relay electrical signals down a patient's damaged spinal cord, perhaps even helping them to walk again. The technology could also be utilized to stimulate the separate chambers of a patient's defective heart, allowing it to beat normally.
For the experimental new system, a Rice University team led by Asst. Prof. Kaiyuan Yang modified existing tiny implants that are temporarily powered by an externally applied alternating magnetic field. That field is generated by a battery-powered transmitter, which could conceivably be worn by the patient on a belt or harness.
The device currently has a range of 60 mm (2.3 in), although that figure may rise as the system is developed further.
When the transmitter emits an electromagnetic pulse, all of the implants within range are simultaneously powered up. That said, each one is programmed to emit a stimulating electrical pulse of its own after a different number of milliseconds have elapsed. This means that they fire one after the other, despite the fact that they were all powered at the same time.
"Each implant has a programmable timer that controls the delay and pulse width of stimulation," Yang tells us. "All devices are first synchronized to the external transmitter in time and then they add their own delay on top of the synchronized clock. Therefore we can control the precise timing of all implants."
In lab tests conducted so far, the technology has been successfully used to trigger responses along a rat's sciatic nerve, and to cause two hydras (a type of tiny tentacled freshwater animal) to contract in sequence.
"We show it’s possible to program the implants to stimulate in a coordinated pattern," says Yang. "We synchronize every device, like a symphony. That gives us a lot of degrees of freedom for stimulation treatments, whether it’s for cardiac pacing or for a spinal cord."
Source: Rice University
