Extended Data Fig. 5: Numerical and experimental assessments of heat accumulation to guide stimulation parameters.
From: Patterned wireless transcranial optogenetics generates artificial perception
(a) Left, image of micro-fabricated thermistor for measuring temperature; middle, schematic illustration of the experimental setup for measuring heat accumulation in the structures surrounding the optical-neural interface; right, image of experimental setup, with wires connected to the thermistors to collect resistance value. Scale bar: 500 µm. (b) Calibration curves of thermistors used in this study for measuring the temperature increase on the surface of skull (left), on the surface of brain (middle), and below the µ-ILED (right). Each dot represents one resistance measurement at one temperature measurement. The best-fit line represents the linear regression between resistance and temperature. n = 1 representative thermistor at each location (skull, brain, or µ-ILED). (c) Simulated (Top) and measured (bottom) results of temperature increase below the µ-ILED for 3 s μ-ILED operation. The temperature increases in a 20 × 300 × 300 µm3 volume, 100 µm below the μ-ILED surface, was output from the numerical model. The thermistor was manually placed and adhered to the μ-ILED surface, followed by a complete procedure of μ-ILED array fabrication. Measured data are presented as mean ± s.e.m. n = 3 technical replicates. Technical replicates are included to account for fluctuations in environmental temperature. (d) Left, simulated maximal temperature increases on the skull surface during μ-ILED operation with 10% duty cycle at varying frequencies. Right, same as left, but for varying duty cycles at 10 Hz. The finite element node with maximal temperature increase (max. node) was selected for plotting. (e) Same as (d), but for brain surface. (f) Left, measured temperature increases on the skull surface during μ-ILED operation with 10% duty cycle at varying frequencies. Right, same as left, but for varying duty cycles at 10 Hz. (g) Same as (f), but for brain surface. (h) Heatmap showing simulated heat production during a single μ-ILED operation in air at 100% duty cycle and 1.93 mW power for 10 s. Left, fPCB array patch without modification. Right, fPCB array patch coated with 100 µm Cu on the rear side. (i) Simulated temperature increases with or without device surface modification with 100 µm Cu.
