In Vitro Reconstruction of Axonal Heat Sensing with a Photothermal Nerve-on-a-Chip.

Axons are the initial sites of thermal signal detection and transduction, but their localized response to heat remains poorly characterized. Here, we present a photothermal nerve-on-a-chip platform that reconstructs in vitro the key elements of axonal thermosensation. By integrating graphene-based photothermal heaters with microelectrode arrays inside axon-guiding microchannels, the platform enables localized, millisecond-scale thermal stimulation and simultaneous extracellular recording of action potentials. Using this platform, we uncovered rapid and reproducible heat-evoked responses in rat dorsal root ganglion neurons, including thermoreceptor-mediated rapid desensitization. With its ability to distinguish stimulus-locked and inter-pulse activity, we also observed distinct thermal-response profiles in human iPSC-derived sensory neurons, characterized by delayed heat responsiveness. Our platform enables high-resolution analysis of axonal temperature coding and is a scalable tool for exploring peripheral thermosensation in development and disease.