MIT Researchers Develop Battery-Free Wearable Devices for Neurons

Researchers at MIT have developed innovative wearable devices that interact with individual cells in the body, particularly neurons, measuring and modulating their activity. These devices, made from a soft polymer called azobenzene, are battery-free and subcellular-sized, allowing them to gently wrap around neuronal structures like axons and dendrites without causing damage. Activated by light, these wireless devices can snugly enfold the neuronal processes, enabling the measurement of electrical and metabolic activity at a subcellular level.

The concept allows for thousands of these tiny devices to be injected into the body, where they can be actuated noninvasively. By controlling the dose of light, researchers can precisely manipulate how these devices wrap around cells, potentially aiding in restoring neuronal degradation seen in diseases like multiple sclerosis. "The concept and platform technology we introduce here is like a founding stone that brings about immense possibilities for future research," says Deblina Sarkar, senior author of the study published in *Nature Communications Chemistry*.

The researchers faced challenges in creating bioelectronic implants that conform to the complex shapes of brain cells, which can vary widely in length and curvature. To address this, they developed thin-film devices that roll into microtubes when exposed to light, allowing them to gently wrap around highly curved axons and dendrites. By fine-tuning the intensity and polarization of the light, they can control the devices’ rolling diameter, enabling a snug fit around the fragile neuronal structures.

The fabrication process involved depositing azobenzene onto a water-soluble sacrificial layer, molding it with a stamp to create thousands of tiny devices, and using light to actuate them. The devices maintained their shape for days post-illumination, and biocompatibility tests showed that they could tightly wrap around rat neurons without causing harm.

The potential applications of these devices are significant, including their use as synthetic myelin to restore insulation around damaged axons, a critical function lost in conditions like multiple sclerosis. The researchers also plan to integrate the devices with optoelectrical materials for cell stimulation and to pattern atomically thin materials for enhanced functionality.

Sarkar expressed excitement over the intimate interface achieved between the devices and living cells, stating, "We have shown that this technology is possible," and highlighted the potential for these devices to modulate neuronal activity with minimal energy requirements, paving the way for new treatments for brain diseases.