Injectable electronics

Charles Lieber, the Mark Hyman Jr. Professor of Chemistry at Harvard University, led a team of international researchers to develop a method for fabricating nano-scale electronic scaffolds that can be injected into the human body via syringe. Once connected to electronic devices, the scaffolds can be used to monitor neural activity, stimulate tissues, and promote regeneration of neurons.

Merging the biological with the electronic is not a new idea for Lieber. In a previous study, scientists in his lab demonstrated that the scaffolds could be used to create cyborg tissue – when cardiac or nerve cells were grown with embedded scaffolds. Researchers were then able to use the devices to record electrical signals generated by the tissues and measure changes in those signals as they administered cardio- or neuro- stimulating drugs.

“We were able to demonstrate that we could make this scaffold and culture cells within it, but we didn’t really have an idea how to insert that into pre-existing tissue,” says Lieber. “But if you want to study the brain or develop the tools to explore the brain-machine interface, you need to stick something into the body. When releasing the electronics scaffold completely from the fabrication substrate, we noticed that it was almost invisible and very flexible like a polymer and could literally be sucked into a glass needle or pipette. From there, we simply asked, would it be possible to deliver the mesh electronics by syringe needle injection, a process common to delivery of many species in biology and medicine. You could go to the doctor, and you inject this, and you’re wired up.”

Deep brain stimulation has been used to treat many disorders for decades, but the nano-fabricated scaffolds operate on a different scale.

“Existing techniques are crude relative to the way the brain is wired,” Lieber explains. Silicon probes and flexible polymers “cause inflammation in the tissue that requires periodically changing the position or the stimulation. But with our injectable electronics, it’s as if they’re not there at all. They are 1 million times more flexible than any state-of-the-art flexible electronics and have subcellular feature sizes. They’re what I call neuro-philic – they actually like to interact with neurons.”

Similar to microchip etching, the process begins with a dissolvable layer deposited on a substrate. To create the scaffold, researchers lay out a mesh of nanowires sandwiched in layers of organic polymer. The first layer is then dissolved, leaving a flexible mesh, which can be drawn into a syringe needle and administered like any other injection.

After injection, the input/output of the mesh can be connected to standard measurement electronics so that the integrated devices can be addressed and used to stimulate or record neural activity. Researchers hope to get a better understanding of how the brain and other tissues react to the injectable electronics over long periods of time.

“This could, I think, make a huge impact on neuroscience,” Lieber says.

Lieber Research Group,
Harvard University
cml.harvard.edu