Researchers in Japan have developed a tiny optical implant, no bigger than the width of a coin, that could be used to change neural behavior. The researchers can implant the device several centimeters into the body, and then activate it externally using infrared light. The device could make it easier for researchers to identify the role of specific neuro circuits in neurological diseases, helping them to develop new treatments.
The field of optogenetics involves activating neurons using light, and this method has helped scientists to learn more about complicated neural circuitry, and its role in disease. Typically, this approach involves optical implants that can deliver light to neurons, such as those in the brain. In fact, researchers have been able to control the behavior of rodents using such optical implants. This technique may also have direct therapeutic potential in areas as diverse as spinal cord injuries and depression.
However, optical implants are typically bulky and uncomfortable, and are comparable to wearing something heavy on the head, such as a football helmet. If optogenetics were ever to be used therapeutically, current implants would likely be difficult for patients to use in the long-term.
The group of Japanese researchers set out to miniaturize an optical implant. So far, this has proved difficult, as many implants rely on electromagnets, meaning that reducing their size also reduces their power. To avoid this, the research team turned to photovoltaics, which is more amenable to miniaturization.
“We integrated two sets of photovoltaic cells onto semiconductor chips,” said Takashi Tokuda, a researcher involved in the study. The implant contains an LED chip, which emits blue light that can activate certain light-sensitive neural proteins. However, the researchers can use infrared light to activate the implant, as this light can easily penetrate tissue, meaning they can implant the sensor up to several centimeters deep in the body.
The implant is just 2.3 milligrams in weight and 1 cubic millimeter in volume. The researchers have described it as “the world’s smallest wireless optical neural stimulator.”
Study in AIP Advances: 1 mm3-sized optical neural stimulator based on CMOS integrated photovoltaic power receiver…