High-precision neural stimulation by a highly efficient candle soot fiber optoacoustic emitter

Abstract

Highly precise neuromodulation with a high efficacy poses great importance in neuroscience. Here we developed a candle soot fiber optoacoustic emitter (CSFOE), capable of generating a high pressure of over 10 MPa with a central frequency of 12.8 MHz, enabling highly efficient neuromodulation in vitro. The design of the fiber optoacoustic emitter, including the choice of the material and the thickness of the layered structure, was optimized in both simulations and experiments. The optoacoustic conversion efficiency of the optimized CSFOE was found to be 10 times higher than the other carbon-based fiber optoacoustic emitters. Driven by a single laser, the CSFOE can perform dual-site optoacoustic activation of neurons, confirmed by calcium (Ca2+) imaging. Our work opens potential avenues for more complex and programmed control in neural circuits using a simple design for multisite neuromodulation in vivo.

High-precision photoacoustic neural modulation uses a non-thermal mechanism

“…Under the laser condition of 45 µJ per pulse, the FE produced an ultrasound waveform with a peak-to-peak pressure of over 8 MPa ( Fig. 1b ), which is consistent with previously published results and is sufficient for efficient PA neurostimulation 20 . When coupled with the CW laser, the FE functions as a pure PT source and generates a very localized thermal field ( Fig.…”

“…We also performed mCherry temperature measurements under PA conditions. Based on previously reported studies 20 , the PA signal generated by a burst of nanosecond pulsed laser of 3 ms is sufficient to activate neurons. Here, maintaining the average laser power at 120 mW, the same as the PT laser condition, a pulse train (1030 nm, 3 ns, RPMC, Fallon, MO, USA) of 3 ms duration was applied to the FE and the fluorescence intensity of mCherry was monitored ( Fig.…”

“…Candle soot was chosen as the absorber due to its great absorption coefficient. The multimode optical fiber was exposed the candle flame for around 3-5 seconds until the fiber tip was fully coated, with the thickness of candle soot controlled by the deposition time 20 . To prepare PDMS, the silicone elastomer (Sylgard 184, Dow Corning Corporation, USA), was carefully dispensed into a container to minimize air entrapment, and then mixed with the curing agent in a ratio of 10:1 by weight.…”

Multifunctional Fiber‐Based Optoacoustic Emitter as a Bidirectional Brain Interface

“…[43,44] Recently, our work showed that fiber-based optoacoustic emitters can also be applied to neural stimulation in vitro and in vivo, with single neuron resolution and dual site capability. [39,45] In these studies, typically commercial silica fibers were used, together with optoacoustic coating. However, the silica fiber, with Young's modulus of approximately70 GPa, is mismatched with mechanical properties of native neural tissue (kilo-to mega pascals) [2] and not easy to integrate with miniaturized electrodes for recording.…”

Functional material-mediated wireless physical stimulation for neuro-modulation and regeneration

“…144 A number of photoacoustic converters based on optical fibres have been developed for neuro-modulation. 142,143,235 Cheng's team reported a miniaturized fibre-optoacoustic converter (FOC) for neuro-modulation at submillimeter spatial precision. 142 The FOC tip is coated with a nanocomposite, which is composed of an absorption layer (graphite/epoxy) and a diffusion layer (ZnO NPs/epoxy).…”