Organ-on-chip devices have provided the pharmaceutical and tissue engineering worlds much hope since they arrived and began to grow in sophistication. However, limitations for their applicability were soon realized as they lacked real-time monitoring and sensing capabilities. The users of these devices relied solely on endpoint analysis for the results of their tests, which created a chasm in the understanding of life between the lab the natural world. However, this gap is being bridged with sensors that are integrated into organ-on-chip devices. This review goes in-depth on different sensing methods, giving examples for various research on mechanical, electrical resistance, and bead-based sensors, and the prospects of each. Furthermore, the review covers works conducted that use specific sensors for oxygen, and various metabolites to characterize cellular behavior and response in real-time. Together, the outline of these works gives a thorough analysis of the design methodology and sophistication of the current sensor integrated organ-on-chips.

Traumatic brain injury and other neurological disorders continue to affect many worldwide and demand further research. It has been shown that electrical signaling and ion channel flow and dynamics are disrupted over the course of a traumatic brain injury as well as over the course of other neurological disorders. However, typical devices used to measure ion flow and electrical signaling from the brain suffer from complexity, high expense, poor spacial and temporal resolution, and low signal to noise ratios. Graphene has emerged as an economical and simple alternative to sensing electrical and ionic signals in a variety of biological situations. This material has emerged as a power material due to its excellent strength, electrical conductivity, and biocompatibility. This review paper focuses on the advantages of the different graphene-based electronic devices and how these devices are being developed into biosensors capable of sensing neuronal ionic and electrical activity and activity from other electrically excitable cells.