Customizing Multifunctional Neural Interfaces through Thermal Drawing Process

Abstract

Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low-loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here we introduce two fabrication approaches: (1) an iterative thermal drawing with a soft, low melting temperature (Tm) metal indium, and (2) a metal convergence drawing with traditionally non-drawable high Tm metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low-impedance metallic electrodes and low-loss waveguides, capable of recording optically-evoked and spontaneous neural activity in mice over several weeks. We couple these fibers with a light-weight mechanical microdrive (1g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, we demonstrate the compatibility of these fibers with magnetic resonance imaging (MRI) and apply them to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber-based neural probes in neuroscience and neuroengineering.

Opsin-free optical neuromodulation and electrophysiology enabled by a soft monolithic infrared multifunctional neural interface

“…This specific metal was selected for the integrated electrodes due to its relatively low melting point (⁓155 °C) and low Young's modulus compared to other metals. Moreover, indium has been recently reported to be a suitable material for EE electrodes [21]. The choice of high-performance polymers with high melting points (>200 °C) as starting materials was critical in achieving the desired outcome, since it allowed the use of any metal with a melting point lower than the fibre's materials as electrodes.…”

“…Several groups around the globe have already reported innovative multifunctional brain devices such as polymer fibres and new soft planar implantable technologies. [3,[20][21][22][23][24]. However, developing of infrared (IR) counterparts to these technologies suitable for in vivo INM in the brain remains a challenge.…”

Micro/nanofiber fabrication technologies for wearable sensors: a review

“…Anikeeva's group also demonstrated a hydrogel hybrid fiber sensor fabricated with thermal drawing, which can also perfectly match the neural tissues and be directly inserted into the deep brain regions with minimized damages [52]. Another work from this group was the implementation of two thermal drawing approaches, which were iterative thermal drawing and convergencedrawing [53]. Based on the technique, multifunctional polymer fibers were delivered and integrated into a microdrive post-implanted into a freely moving mouse.…”

Microstructured Electroceutical Fiber‐Device for Inhibition of Bacterial Proliferation in Wounds

“…Multimaterial fiber-device technology [20,21] has enabled fibers and textiles to hold a vast new array of functional properties. Specifically, in biomedical applications, fiber devices have been used for signal transduction, sensing, and processing in braincomputer interfaces, [22] microfluidics, [23] acoustics, [24] targeted drug delivery, [25] chemical sensing, [26] imaging systems, [27] wearable fabric devices, [28] and more. To our knowledge, we are the first to introduce a multimaterial fiber incorporating electroceutical therapy into a suture, [29] as illustrated in Figure 1a.…”