This review is specifically focusing on different methods used to fabricate graphene as a flexible electrode.

Due to the particular structure and functionality of the placenta, most current human placenta drug testing methods are limited to animal models, conventional cell testing, and cohort/controlled testing. Previous studies have produced inconsistent results due to physiological differences between humans and animals and limited availability of human and/or animal models for controlled testing. To overcome these challenges, a placenta‐on‐a‐chip system is developed for studying the exchange of substances to and from the placenta. Caffeine transport across the placental barrier is studied because caffeine is a xenobiotic widely consumed on a daily basis. Since a fetus does not carry the enzymes that inactivate caffeine, when it crosses a placental barrier, high caffeine intake may harm the fetus, so it is important to quantify the rate of caffeine transport across the placenta. In this study, a caffeine concentration of 0.25 mg mL⁻¹ is introduced into the maternal channel, and the resulting changes are observed over a span of 7.5 h. A steady caffeine concentration of 0.1513 mg mL⁻¹ is reached on the maternal side after 6.5 h, and a 0.0033 mg mL⁻¹ concentration on the fetal side is achieved after 5 h.

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.

In the past few decades, the placenta became a very controversial topic that has had many researchers and pharmacists discussing the significance of the effects of pharmaceutical drug intake and how it is a possible leading cause towards birth defects. The creation of an in vitro microengineered model of the placenta can be used to replicate the interactions between the mother and fetus, specifically pharmaceutical drug intake reactions. As the field of nanotechnology significantly continues growing, nanotechnology will become more apparent in the study of medicine and other scientific disciplines, specifically microengineering applications. This review is based on past and current research that compares the feasibility and testing of the placenta-on-a-chip microengineered model to the previous and underdeveloped in vivo and ex vivo approaches. The testing of the practicality and effectiveness of the in vitro , in vivo and ex vivo models requires the experimentation of prominent pharmaceutical drugs that most mothers consume during pregnancy. In this case, these drugs need to be studied and tested more often. However, there are challenges associated with the in vitro , in vivo and ex vivo processes when developing a practical placental model, which are discussed in further detail.

The unique attribute of transient technology is that it promotes the potential for the design and implementation of sustainable systems through their capability to fully or partially disintegrate after a predefined period of stable operation. Transient electronics have a wide range of potential applications as biomedical implants, environmental sensors, and hardware‐secured devices. Controlled disintegration of such systems without the need for harsh solvents is a step toward realizing green and sustainable electronics. In this short review, recent progress in the development of transient electronics is studied. First, an overview of the transient materials, both the substrate and electronic component, is described. Second, the mechanisms under which transiency occurs, including aqueous dissolution and thermal degradation, are reported. Third, manufacturing techniques for the fabrication of transient electronics are reviewed. And last, various transient electronic devices and their applications are discussed.