Low-temperature (≤ 350 °C) aluminum-induced layer exchange enables the integration of large-grained polycrystalline silicon–germanium layers into silicon-based optical, electronic, and electromechanical sensors, either in post-processing or at the back-end-of-line of a CMOS flow. We systematically investigate how annealing conditions, metal composition, diffusion control layer, and Al/a-Ge thicknesses influence the crystallization process and the resulting silicon–germanium layer. Our results reveal tunable correlations between process parameters and layer properties, demonstrating that both the crystallinity and the composition of the final layer can be precisely controlled. This work provides practical guidelines for tailoring aluminum-induced layer exchange for silicon–germanium integration across diverse device applications.

We present a novel silicon-based organ-on-chip (OoC) device featuring integrated microelectrodes to assess barrier function in biological tissue co-cultures. The microfluidic device consists of two vertically-stacked microchannels separated by a submicron-thin, microporous silicon nitride membrane, enabling in vivo-like proximity for co-cultured tissues. The integrated four-probe electrode geometry on slanted microchannel sidewalls ensures unobstructed optical access to the membrane and consistent measurement repeatability. Experimental validation through electrical impedance spectroscopy supported the device's sensitivity to sodium chloride concentration. Fabricated through a scalable, wafer-scale batch process, the device additionally demonstrated biocompatibility and optical transparency, representing a significant advancement for in situ tissue barrier assessments.

The mechanisms governing the onset and eventual progression of several neurodegenerative disorders remain poorly understood or even undiscovered. This lack of pathophysiological insight can be partly attributed to reliance on inaccurate in vitro models. Notwithstanding research efforts towards recapitulating brain functions on flat devices, mimicking the brain's three-dimensional (3D) architecture in vitro remains a prime target, as 3D models more closely resemble the functional behavior and dynamic responses of in vivo organs. In this work, we present a novel, wafer-scale approach for microfabrication of soft and transparent 3D microelectrode arrays (MEAs) for in vitro electrical recording and optical inspection of electrogenic cell cultures. The proposed 3D MEAs entail 90μ m -high polydimethylsiloxane-based micro-pyramids featuring multiple, electrically-distinct and vertically-stacked titanium nitride electrodes on their slanted facets. Our innovative 3D MEAs will facilitate the development of physiologically-accurate brain-on-a-chip models capable of monitoring 3D electrical communication in neuronal networks while allowing their simultaneous optical characterization.

We present the fluidic and electrical packaging of a novel silicon-based trans-epithelial electrical resistance (TEER) sensor chip designed for a modular and standardized organ-on-chip (OoC) platform. The package comprises three key components: the housing of the TEER chip, microfluidic routing for seamless integration with the platform, and electrical connections to a platform-integrated potentiostat. This modular solution enables continuous impedance measurements while maintaining unobstructed optical access to the tissue culture region. Experiments confirmed leak-free fluid flow across the stacked microfluidic channels and stable sensitivity of TiN electrodes to PBS. The TEER module retains optical transparency, bi-ocompatibility, and industrial scalability, supporting advanced in situ tissue barrier assessments in standardized OoC systems.