Stimulation of ChR2 neurons was achieved by a custom-built laser setup consisting of a solid-state laser (Sapphire, Coherent, Dieburg, Germany) with a wavelength of 488 nm and a maximal output power of 20 mW.
For a two-layer FH-TENG, it can deliver a maximal output voltage of 191 V and an instantaneous output power of 64μW on the external load of 210MΩ at a frequency of 0.8 Hz and a force of ∼20 N.
With optimized layer structures 5-mm wide laser bars at 650 nm with a maximal output power of 55 W in pulsed operation were realized.
A tunable fiber laser from the company Keopsys with a maximal output power of 5 W (linewidth ≈ 2 GHz) is used for optical pumping.
The system is also equipped with a 785-nm diode laser for excitation, which has a maximal output power of 300 mW at the source.
Considering maximal energy transfer in this frequency range, i.e. a maximal output, especially in case of professional classical singing under consideration of the so-called singer's formant cluster in males, these behaviour seems to be plausible and very effective.
For this reason, results establishing a non-monotonic transfer function with a maximal output at intermediate input are of high significance for the modeling of neuronal assemblies (Kuhn et al. 2004).
To achieve constraint fulfillment and to evaluate tracking performance, the reference management is reduced into a convex quadratic programming problem using the concept of a maximal output admissible set.
Stimulation intensity, expressed as a percentage of the maximal output of the stimulator, was kept between 40 75% for all subjects, corresponding to an electric field between 110 120 V/m on the cortical surface.
Focal TMS was performed using a figure-of-8 shaped magnetic coil (outer diameter, 70 mm) connected to a Magstim BiStim magnetic stimulator (Magstim Co, Wales, UK), with maximal output of 2.2 T (see the Supplementary material for full details).
