Hydrogel membranes in organ-on-a-chip devices: A review

Organ-on-a-chip (OoC) devices represent advanced in vitro models enabling to mimic the human tissue architecture function and physiology, providing a promising alternative to the traditional animal testing methods. These devices combine the microfluidics with soft materials, specifically hydrogel membranes (HMs) for mimicking the extracellular matrix (ECM) and biological barriers, such as the blood-brain barrier (BBB). Hydrogels are ideal biomaterials for OoC systems because of their tunable properties, biocompatibility, biodegradability, and microscale self-assembly. The integration of HMs with OoC devices provides an effective way to develop dynamic, biologically relevant environments for supporting living cells targeted at drug discovery, disease modeling, and personalized medicine. Recent advancements in fabrication technologies such as additive manufacturing (3D printing), photolithography, and bioprinting have additionally advanced development of such systems. This review aims to outline the role of HMs in OoC platforms, highlighting their material properties, self-assembly behavior, and also challenges associated with their fabrication. Additionally, we visualize and discuss the latest progress made in utilizing HMs for applications in tissue engineering, drug development, and biosensing, with a focus on their interface dynamics and structural self-organization. The future perspective on OoC technology has also been patterned in order to provide a broader image on integration of OoC and HMs with personalized medicine and advanced drug delivery systems.