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Brain is one of the most temperature sensitive organs. Besides the fundamental role of temperature in cellular metabolism, thermal response of neuronal populations is also significant during the evolution of various neurodegenerative diseases. For such critical environmental factor, thorough mapping of cellular response to variations in temperature is desired in the living brain. So far, limited efforts have been made to create complex devices that are able to modulate temperature, and concurrently record multiple features of the stimulated region. In our work, the in vivo application of a multimodal photonic neural probe is demonstrated. Optical, thermal, and electrophysiological functions are monolithically integrated in a single device. The system facilitates spatial and temporal control of temperature distribution at high precision in the deep brain tissue through an embedded infrared waveguide, while it provides recording of the artefact-free electrical response of individual cells at multiple locations along the probe shaft. Spatial distribution of the optically induced temperature changes is evaluated through in vitro measurements and a validated multi-physical model. The operation of the multimodal microdevice is demonstrated in the rat neocortex and in the hippocampus to increase or suppress firing rate of stimulated neurons in a reversible manner using continuous wave infrared light (λ = 1550 nm). Our approach is envisioned to be a promising candidate as an advanced experimental toolset to reveal thermally evoked responses in the deep neural tissue.

A SANS study of 0.073 c micellar solutions of sodium alkyl sulfates with chain length from n C = 9 to 16 was carried out. Micelles were assumed to be ellipsoids which may grow only in the direction of their axis of symmetry. The structure factor was calculated in terms of the one-component macrofluid model by assuming DLVO potential. The contact radius and the strength of the interaction potential were handled as free fitting parameters; the electrostatic potential and the apparent micellar charge on the contact surface were derived from the latter. The assumptions imposed on the conformation of the micellar cores are sustained by the best-fit parameters of the form-factor. For n C = 9−13 the mean aggregation numbers are in good, or at least, in acceptable agreement with the predictions of a recent thermodynamic theory of micellization. The difference found between the mean core and contact radii suggests that an unknown repulsive interaction may be present which prevents the micelles from astructurally possiblecloser approach. Although the surface potential indicates that the outgoing conditions for deriving the DLVO potential are violated, the agreement of the electric charge derived partly from the DLVO potential, partly from the nonlinearized Gouy−Chapman model supports the practical applicability of the well-known DLVO potential formula to interpreting SAS results.

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