Fully-Flexible Multifunctional Polydimethylsiloxane (PDMS) Neural Probe With a U-Turn Polyester Microchannel

This study aims to develop a flexible, implantable neural probe with tunable stiffness and multifunctionality for electrophysiology, drug delivery, and optogenetics, while minimizing immune response.

The probe was fabricated from polydimethylsiloxane (PDMS) with a U-turn polyester-filled microchannel (30 μm × 30 μm, 14.7 mm length). Polyester provides rigidity at room temperature and softens near body temperature for tissue compatibility. Mechanical simulations optimized probe dimensions (60 μm × 300 μm × 7 mm), ensuring insertion forces above 1.5 mN. A microfluidic mixer (90 μm × 30 μm, 7 mm) was integrated for controlled drug delivery. Heat transfer and fluid simulations assessed thermal stability and laminar flow. The device also included four gold electrodes, a bio-amplifier, and a blue μ-LED.

Experiments confirmed stable channel performance with no leaks or bubbles, effective heat management at 37 °C, and a 60° tip angle as optimal for insertion. The probe consumed ∼46.6 mW and enabled reliable electrophysiological recordings and fluorescence activation in vitro. Biocompatibility testing validated its suitability for long-term implantation.

The PDMS-polyester probe achieves thermally controlled stiffness, precise drug delivery, and integrated optogenetic stimulation while maintaining stable electrophysiological recording performance.

This work introduces a multifunctional neural probe that addresses limitations of rigid implants by combining flexibility, drug delivery, and optogenetics. The platform has strong potential for advancing long-term neuroengineering applications, reducing tissue response, and enabling multimodal brain interfacing.