Indium tin oxide (ITO) has recently gained prominence as a photonic nanomaterial, for example, in modulators, tuneable metasurfaces and for epsilon-near-zero (ENZ) photonics. The optical properties of ITO are typically described by the Drude model and are strongly dependent on the deposition conditions. In the current literature, studies often make several assumptions to connect the optically measured material parameters to the electrical properties of ITO, which are not always clear, nor do they necessarily apply. Here, we present a comprehensive study of the structural, electrical, and optical properties of ITO and showed how they relate to the deposition conditions. We use guided mode resonances to determine the dispersion curves of the deposited material and relate these to structural and electrical measurements to extract all relevant material parameters. We demonstrate how the carrier density, mobility, plasma frequency, electron effective mass, and collision frequency vary as a function of deposition conditions, and that the high-frequency permittivity (${\mathsf{ϵ}}_{\infty }$) can vary significantly from the value of ${\mathsf{ϵ}}_{\infty }$ = 3.9 that many papers simply assume to be a constant. The depth of analysis we demonstrate allows the findings to be easily extrapolated to the photonic characterisation of other transparent conducting oxides (TCOs), whilst providing a much-needed reference for the research area.

Complex diseases arise from networks of interacting biomolecules, yet most analytical technologies measure only a limited number of interactions simultaneously. Here, we present a chirped guided-mode resonance (cGMR) photonic biosensor array for multiplexed, label-free analysis of biomolecular kinetics across hundreds of sensing sites. The platform integrates 322 photonic sensors on a single chip that are fabricated using a CMOS process ensuring high reproducibility (wavelength sensitivity of 36.8 pixels/nm with a standard deviation of 1.37 pixels/nm). Shifts in the photonic resonance due to molecular binding are recorded using a conventional CMOS camera allowing time-resolved and simultaneous measurements across the entire array. We demonstrate the platform's versatility by monitoring real-time binding of antibodies, aptamers, and synthetic glycopolymers where the parallel measurements reveal distributions of binding responses arising from surface heterogeneity and multivalency that are inaccessible to conventional, single biosensor platforms. As a model, wheat germ agglutinin binding to a GlcNAc-displaying glycopolymer yielded sub-micromolar equilibrium dissociation constants (K_D = 28-564 nM). Crucially, the array successfully resolves the kinetics of lectin-glycopolymer binding interactions using a portable optical setup, even in a complex biological matrix. By combining scalable CMOS fabrication with portable, highly parallel interrogation, this cGMR array provides a robust route toward high-throughput biomolecular profiling in point-of-care diagnostics and drug discovery.

Nanoimprint lithography is a technique that promises a low-cost, high-throughput, and high-resolution method for fabricating nanostructures, which may be used in communications, sensing, and emerging technologies such as augmented reality glasses. We present a comprehensive analysis of an ultraviolet nanoimprint lithography protocol using a resin-stamp platform, introduced by OpTool AB, for the production of 1D and 2D guided mode resonance grating structures. We assess their performance optically, a method rarely reported, to investigate the device functionality and make practical comparisons to electron-beam lithography. We achieve a representative resolution of 30 nm, which leads to good optical resonances, but we also note issues with inconsistent patterning over large areas ( > 1 mm ² ) and short shelf-lives of the chemicals involved. We conclude that, while Nanoimprint lithography can fabricate structures on a par with electron beam lithography, it also presents some challenges in producing functional devices at lower throughputs, a key consideration for small research laboratories.