A very small implantable device that can be used to control brain patterns has been developed by Japanese researchers using photovoltaic technology. The device is both the smallest and the lightest wireless optical biodevice to have ever been developed.
With it long been known in the field of optogenetics that chemicals can change their neural behaviour through different exposures to light, is has now been shown that the light also has the capacity to activate proteins in the brain, changing the brains patters.
Traditionally scientists have been implanting helmet-type optical devices on rodents to successfully control their brain activity. However the size of these devices has been a source of stress and discomfort to the animals.
Tasashi Tokuda of the Nara Institute of Science and Technology and her team have been researching ways to make the technology smaller: “Size is always the challenge. No one likes having large implants,” he said. According to the scientists, the dependency of implantable devices on electromagnetics is what has hindered the miniaturization of wearable devices, with the voltage alongside the current decrease with a reduction in size, which limits the device’s power.
Photovoltaic technology however has allowed the devices to become smaller due to the voltage on these devices not diminishing alongside their size. Devices that use photovoltaics as a power source, see their voltage remain unchanged as they get smaller. The device that the team has developed uses a complementary metal-oxide semiconductor that controls photovoltaic power.
“We integrated two sets of photovoltaic cells onto semiconductor chips. Ten cells were integrated for powering, and seven cells for biasing,” Tokuda explained.
The small device can be implanted within the body due to its use of infrared light, and measures a tiny 1mm and weighs 2.3mg and has been called “the world’s smallest wireless optical neural stimulator.”