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.

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.

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.

Demand for biocompatible, non-invasive, and continuous real-time monitoring of organs-on-chip has driven the development of a variety of novel sensors. However, highest accuracy and sensitivity can arguably be achieved by integrated biosensing, which enables in situ monitoring of the in vitro microenvironment and dynamic responses of tissues and miniature organs recapitulated in organs-on-chip. This paper reviews integrated electrical, electrochemical, and optical sensing methods within organ-on-chip devices and platforms. By affording precise detection of analytes and biochemical reactions, these methods expand and advance the monitoring capabilities and reproducibility of organ-on-chip technology. The integration of these sensing techniques allows a deeper understanding of organ functions, and paves the way for important applications such as drug testing, disease modeling, and personalized medicine. By consolidating recent advancements and highlighting challenges in the field, this review aims to foster further research and innovation in the integration of biosensing in organs-on-chip.