Flexible\nAcetylcholine Neural Probe with a Hydrophobic\nLaser-Induced Graphene Electrode and a Fluorous-Phase Sensing Membrane

This work develops the first laser-induced graphene (LIG)-based\nelectrochemical sensor with a superhydrophobic fluorous membrane for\na flexible acetylcholine (ACh) sensor. ACh regulates several physiological\nfunctions, including synaptic transmission and glandular secretion.\nThe ACh sensing membrane is doped with a fluorophilic cation-exchanger\nthat can selectively measure ACh based on the inherent selectivity\nof the fluorous phase for hydrophobic ions, such as ACh. The fluorous-phase\nsensor improves the selectivity for ACh over Na<sup>+</sup> and K<sup>+</sup> by 2 orders of magnitude (compared to traditional lipophilic\nmembranes), thus lowering the detection limit in artificial cerebrospinal\nfluid (aCSF) from 331 to 0.38 μM, thereby allowing measurement\nin physiologically relevant ranges of ACh. Engraving LIG under argon\ncreates a hydrophobic surface with a 133.7° contact angle, which\nminimizes the formation of a water layer. The flexible solid-contact\nLIG fluorous sensor exhibited a slope of 59.3 mV/decade in aCSF and\nretained function after 20 bending cycles, thereby paving the way\nfor studying ACh’s role in memory and neurodegenerative diseases.