Implantable Neural Probe Records Single-Neuron Activity Over Time

Large-scale, long-term recordings of the activity of individual brain neurons are essential for improving our knowledge of neural circuits, developing new medical device-based treatments, and, eventually, developing brain-computer interfaces that need high-resolution electrophysiological data.

An Implantable Device That Captures Months of Single-Neuron Brain Activity
Photograph of elastomer-encapsulated neural probes with four layers of electrode arrays. Image Credit: Jia Liu Group/Harvard SEAS

However, there is currently a trade-off between the length of time an implanted device can continue to record or stimulate performances and the amount of high-resolution information it can measure. Although the device can gather a great deal of data, rigid silicon implants with numerous sensors are unable to remain inside the body for very long. Smaller, flexible devices can stay in the brain longer and are less invasive, but the device can only capture a small portion of the neural data that is there. 

In collaboration with The University of Texas at Austin, MIT, and Axoft, Inc., an interdisciplinary team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) recently created a soft implantable device with dozens of sensors that can record single-neuron activity in the brain steadily for months.

The study was published in Nature Nanotechnology.

We have developed brain–electronics interfaces with single-cell resolution that are more biologically compliant than traditional materials. This work has the potential to revolutionize the design of bioelectronics for neural recording and stimulation, and for brain - computer interfaces.

Paul Le Floch, Study First Author and Assistant Professor, John A. Paulson School of Engineering and Applied Sciences, Harvard University

Currently, Le Floch serves as CEO of Axoft, Inc., a business that Liu, and Tianyang Ye - a former Harvard graduate student and postdoctoral fellow in the Park Group - founded in 2021. The intellectual property related to this research has been safeguarded by Harvard’s Office of Technology Development, which has granted a license to Axoft for additional development.

Fluorinated elastomers are a class of materials that the researchers used to overcome the trade-off between longevity and high-resolution data rate. Teflon and other fluorinated materials are robust, stable in biofluids, exhibit excellent dielectic performance over an extended period, and work well with conventional microfabrication techniques.

Stacks of soft microelectrodes totaling 64 sensors were combined with these fluorinated dielectric elastomers by the researchers to create a long-lasting probe that is 10,000 times softer than traditional flexible probes composed of materials engineering plastics like polyimide or parylene C.

The researchers recorded neural data from mice’s brains and spinal cords over several months to demonstrate the device in vivo.

Our research highlights that, by carefully engineering various factors, it is feasible to design novel elastomers for long-term-stable neural interfaces. This study could expand the range of design possibilities for neural interfaces.

Jia Liu, Study Corresponding Author, John A. Paulson School of Engineering and Applied Sciences, Harvard University

The interdisciplinary research team also included SEAS Professors Katia Bertoldi, Boris Kozinsky and Zhigang Suo.

Designing new neural probes and interfaces is a very interdisciplinary problem that requires expertise in biology, electrical engineering, materials science, mechanical and chemical engineering.

Paul Le  Floch, Study Author, John A. Paulson School of Engineering and Applied Sciences, Harvard University

The research was co-authored by Siyuan Zhao, Ren Liu, Nicola Molinari, Eder Medina, Hao Shen, Zheliang Wang, Junsoo Kim, Hao Sheng, Sebastian Partarrieu, Wenbo Wang, Chanan Sessler, Guogao Zhang, Hyunsu Park, Xian Gong, Andrew Spencer, Jongha Lee, Tianyang Ye, Xin Tang, Xiao Wang and Nanshu Lu.

The study was supported by the National Science Foundation through the Harvard University Materials Research Science and Engineering Center.

Journal Reference:

Paul Le Floch, L. P., et al. (2023) 3D spatiotemporally scalable in vivo neural probes based on fluorinated elastomers. Nature Nanotechnology.


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