Tiny brain implant recharges from outside of body

Researchers in South Korea have developed a brain implant that wirelessly recharges from outside the body to control brain circuits for extended periods.

brain implant
Optical image of a wirelessly rechargeable, soft optoelectronic system held with fingers. The device is emitting blue light from its bilateral probes (Image: KAIST)

Developed by KAIST researchers and their collaborators, the device has been constructed with ultra-soft and bio-compliant polymers. Geared with micrometre-sized LEDs mounted on ultrathin probes, the device is said to wirelessly manipulate target neurons in the deep brain using light.

This study, led by Professor Jae-Woong Jeong, is an advance on the wireless head-mounted implant neural device he developed in 2019 that could indefinitely deliver multiple drugs and light stimulation treatment by using a smartphone.

Smartphone controls therapeutic brain implants

For the latest version, the research team came up with a fully implantable, soft optoelectronic system that can be remotely and selectively controlled by a smartphone. The team’s findings are published in Nature Communications.

Wireless implantable device technologies have become popular as alternatives to conventional tethered implants because they help minimise stress and inflammation in free-moving animals during brain studies, which enhances the lifetime of the devices. Such devices require intermittent surgeries to replace discharged batteries, or bulky wireless power setups, which limit experimental options as well as the scalability of animal experiments.

“This powerful device eliminates the need for additional painful surgeries to replace an exhausted battery in the implant, allowing seamless chronic neuromodulation,” Professor Jeong said in a statement. “We believe that the same basic technology can be applied to various types of implants, including deep brain stimulators, and cardiac and gastric pacemakers, to reduce the burden on patients for long-term use within the body.”

To enable wireless battery charging and controls, researchers developed a circuit that integrates a wireless energy harvester with a coil antenna and a Bluetooth low-energy chip. An alternating magnetic field penetrates through tissue and generates electricity inside the device to charge the battery. Then the battery-powered Bluetooth implant delivers programmable patterns of light to brain cells using a smartphone app for real-time brain control.

“This device can be operated anywhere and anytime to manipulate neural circuits, which makes it a highly versatile tool for investigating brain functions,” said lead author Choong Yeon Kim, a researcher at KAIST.

Neuroscientists tested the implants in rats and demonstrated their ability to suppress cocaine-induced behaviour after the rats were injected with the narcotic. This was achieved by precise light stimulation of relevant target neurons in their brains using the smartphone-controlled LEDs. The battery in the implants could be repeatedly recharged while the rats were moving freely, which minimised any physical interruption to the experiments.

The researchers believe this brain implant technology may lead to new opportunities for brain research and therapeutic intervention to treat diseases in the brain and other organs.