Mid-infrared Photoacoustic Stimulation of Neurons Through Vibrational Excitation in Polydimethylsiloxane

Photoacoustic (PA) emitters are emerging ultrasound sources offering high spatial resolution and ease of miniaturization. Thus far, PA emitters rely on electronic transitions of absorbers embedded in an expansion matrix such as polydimethylsiloxane (PDMS). Here, it is shown that mid-infrared vibrational excitation of C & horbar;H bonds in a transparent PDMS film can lead to efficient mid-infrared photoacoustic conversion (MIPA). MIPA shows 37.5 times more efficient than the commonly used PA emitters based on carbon nanotubes embedded in PDMS. Successful neural stimulation through MIPA both in a wide field with a size up to a 100 mu m radius and in single-cell precision is achieved. Owing to the low heat conductivity of PDMS, less than a 0.5 degrees C temperature increase is found on the surface of a PDMS film during successful neural stimulation, suggesting a non-thermal mechanism. MIPA emitters allow repetitive wide-field neural stimulation, opening up opportunities for high-throughput screening of mechano-sensitive ion channels and regulators. Photoacoustic emitters are emerging ultrasound sources offering high spatial resolution and ease of miniaturization. This work shows mid-infrared vibrational excitation of C & horbar;H bonds in transparent polydimethylsiloxane films leads to highly efficient photoacoustic conversion. Neural stimulation with tunable precision from single cell to 200 mu m diameter is achieved. Mid-infrared photoacoustic stimulation has a potential in high-throughput screening of neuron regulators. image