# UV Laser‐Induced Carbon Microelectrode Arrays for Neuronal Recordings

## TL;DR

Researchers developed flexible carbon electrodes using UV lasers on parylene films, which can record and stimulate neurons effectively.

## Contribution

A one-step UV laser-induced carbonization method for fabricating biocompatible carbon electrodes on parylene-C for neuronal applications.

## Key findings

- UV laser-induced carbonization of parylene-C produces stable, biocompatible electrodes for neuronal recordings.
- Electrodes withstand 10,000 voltage-controlled pulses and maintain performance over 4 weeks in culture.
- Neurons conform well to the rough carbon structures, showing good interface compatibility.

## Abstract

Bioelectronic devices for in vitro and in vivo studies benefit from polymeric materials as substrates and insulations due to their flexible nature. Laser‐induced carbon formation has emerged as a rapid and versatile technique to fabricate conductive carbon‐based structures from insulating polymer films. Here, the development of electrodes fabricated via ultraviolet (UV) laser‐induced carbonization of chlorinated poly‐p‐xylylene (parylene‐C) insulation areas is reported. The parylene‐derived carbon is directly fabricated over the thin metallization layer, thus opening the desired electrode areas in a one‐step process. The optimal laser parameters for electrode performance are investigated, and the stability of the electrodes is tested under 10 000 voltage‐controlled stimulation pulses. In vitro tests of primary neuronal cultures confirm the biocompatibility of the proposed interfaces and reveal the good conformability of the neurons over the rough carbon structures. The performance of the sensor arrays is shown in electrophysiological recordings of neuronal cultures, together with a proof‐of‐principle stimulation, confirming the stability of the recordings over at least 4 weeks in culture. The proposed laser‐induced carbon electrodes from polymer coating are suitable as a rapid and precise fabrication protocol for carbon‐based sensors, applicable to bioelectronics and neuroelectronics devices.

Thin‐film electrodes are flexible devices of high conformability and minimal dimensions with attractive properties for in vivo and in vitro bioelectronics. Here, electrodes are developed from parylene films via ultraviolet laser‐induced carbonization. The performance of the carbon electrodes in recording and stimulating primary neuronal cultures is tested, and the versatility of the fabrication in various designs is shown.