Fig 1.
Different cellular mechanisms based on photofaradaic, photocapacitive, and excitonic stimulations.
(a) Photofaradaic-capacitive stimulation [8,11], (b) Photocapacitive stimulation of cells with engineered band-alignment in a photovoltaic cell [3,17], and (c) Polarized light modulation inducing electric field redistribution and facilitating capacitive and pixel-wise stimulation based on microdomains in a hybrid organic solar cell without band alignment engineering.
Fig 2.
(a) A cartoon of the photo-induced dipole (demonstrated based on the energy band diagram) in a bulk organic photo-capacitor structure and a grown neuron on the surface of the bio-interface.
(b) Dipole-dipole interaction between photo-induced dipoles and the electrical charges across the cell lipid bilayer (without considering the effect of the electrical double layer). (c) Unaligned and aligned dipole microdomains induced by polarized light in a photovoltaic organic hybrid system. Each microdomain represents localized excitonic regions formed upon photoexcitation, with alignment enhanced under polarization, illustrating the anisotropic photoresponse of the hybrid material.
Table 1.
Ionization energies and redox potentials of biologically relevant ions in aqueous media, highlighting their role in photo-faradaic interactions at the biointerface. These parameters are critical for understanding how photoelectrode Fermi levels facilitate or restrict ion redistribution, membrane depolarization, and capacitive or electrochemical neural stimulation.
Table 2.
The list of different photo-capacitors and calculated photo-induced dipoles for polarization modulation. (See the methodology section supplementary information).
Table 3.
The list of different photovoltaic substrates and calculated photo-induced dipoles for polarization modulation.
Fig 3.
(a) Chemical structure of PEC12:ITIC, (b) Light absorption spectra compared with control.
(c) Potentiostat for photocurrent and photovoltage measurements. (d), and (e) Photocurrent response of a PCE12:ITIC polymer blend under continuous polarized light illumination. The device exhibits polarization-dependent enhancement in both photovoltage and photocurrent, indicating that anisotropic molecular orientation and dipole alignment modulate charge separation efficiency. The results highlight the role of excitonic field alignment and photocarrier dynamics in polarization-sensitive organic photovoltaic systems.
Fig 4.
(a) Schematic of whole cell patch clamp measurement of an isolated neuron with electrical circuits, (b) Simulated membrane potential Vm(t) in response to a time-varying photovoltage VOC (t) derived from a polarized-light-driven PEC12:ITIC photovoltaic device.
Fig 5.
Hippocampal cell culture, viability, and calcium dynamics on organic solar cell substrates.
(a) Representative fluorescence micrograph of hippocampal neurons cultured directly on the PCE12: ITIC organic solar cell substrate, showing healthy morphology and network formation. (b) Optical density (OD) measurements across PCE12:ITIC, P3HT:PCBM, and Control groups (bars: mean ± SD), with overlaid relative cell viability normalized to Control. (c) Maximum intensity projection from calcium imaging, highlighting manually selected cell regions of interest (ROIs) with distinct color-coded circles (N = 11). (d) Corresponding ΔF/F₀ calcium transients for the ROIs, demonstrating stimulus-evoked intracellular calcium responses and cell-to-cell variability (N = 11). (e) Calcium fluorescence dynamics recorded from hippocampal neurons cultured on PCE12:ITIC solar cell substrates. Individual cell responses are shown in gray, with the population average highlighted in blue. (f) Average calcium signal difference between a cell grown on top of PCE12:ITIC and on the ITO control substrate.
Table 4.
The comparison of the photo-induced dipoles in semiconductor NCs and in metallic and carbon particles measured with the Kelvin probe.
Fig 6.
Polarization modulation for the photo-stimulation of cells with photo-induced electrical dipoles in a photo-capacitive substrate, (a) electrical circuit model for the photoelectrical stimulation of cells through a photocapacitor, (b) Transmission line model for neural stimulation through the radiation of a photo-induced dipole with polarized light effect, (c) Membrane potential induced by a cluster of QDs (nano antennas changing from 5-100 numbers) in contact with a passive cell membrane with the frequency excitation of 5 Hz.
As it is clear, the electric field distribution depends on the frequency of the polarization modulation.
Table 5.
Potential application of the polarization modulation for retinal application [53].
Table 6.
Application table for the anisotropic engineered structure [54].
Table 7.
Fig 7.
Photoinduced dipole modulation of membrane potential and effective capacitance based on polarization modulation of the light.
(a) Simulated membrane potential dynamics under left- and right-circularly polarized light (LCP vs. RCP), demonstrating asymmetric stimulation due to dipole orientation. (b) Hodgkin-Huxley membrane potential response under dipole-induced capacitive stimulation across multiple frequencies (1–100 Hz), highlighting frequency-dependent spiking behavior. (c) Gradual membrane depolarization under continuously rotating polarization (0° → 90°), showing cumulative excitatory effects from spatiotemporal dipole alignment. (d) Extracted effective membrane capacitance as a function of photoinduced dipole amplitude, revealing nonlinear charge displacement and field-membrane coupling.