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.

Due to their functional and biological benefits, shape memory polymer (SMP) stents have attracted the attention of researchers in the biomedical science area. The highlights of this article are the evaluation of stent performance including radial force recovery and recovery start temperature (RST) in a constrained state. The effects of polyurethane (PU) mechanical properties and fabrication method are investigated on thermo-viscoelastic properties, sample defect and shape recovery of PU and polycaprolactone (PCL) blend. Thereafter, three tubular stents fabricated with the different diameter to thickness (d/t) ratio and their mechanical behavior are examined in loading, relaxation, and unloading. Finally, the radial force recovery of the stents is measured after stimulation in temperatures up to 45 °C. Emerging more peaks in the delta tangent graph implies that samples fabricated with solution-mixing has a better viscoelastic behavior and shows fewer defects compared to the melt-mixing ones. The fabrication method was much more effective on enhancement of the storage and loss modulus compared to double increasing of Young's modulus of applied PU from 4.3 to 9 MPa. Moreover, an increase in the stent's d/t from 15 to 10 causes not only an increase in the radial stiffness and force recovery but also leads to the reduction of irreversible deformation and RST. The results of this research reveals the importance of the dimensional and geometric design of SMP stents in controlling the force recovery and RST.

Shape memory polymer composites have attracted significant attention due to novel properties and great applications. In this article, we focus on the fabrication and simulation of polyurethane/polycaprolactone nanocomposites. The polyurethane/polycaprolactone blends containing ZnO nanoparticles (5 to 30 wt%) are fabricated using a solution mixing and casting method. It is found that significant improvement of polyurethane/polycaprolactone composites in Young’s modulus is achieved by incorporating 20 wt% of ZnO nanoparticles; also, the results of the shape recovery ratio reveal that adding an optimum amount of ZnO (the reinforcement) can increase the shape recovery ratio (for 20 wt% of ZnO). These results could most likely be explained by the fact that some particles restrict the hard segment–soft segment interactions and provide more mobility to polycaprolactone components, while the other nanoparticles can act as the nucleating agent for polycaprolactone chains. A generalized Maxwell model is then used to examine the shape memory behavior of shape memory polymer composites. The dynamic mechanical thermal analysis results are utilized to define the model coefficients and the simulation is carried out to determine the shape recovery ratio. Simulation of this shape recovery ratio for shape memory polymer composites reveals that the numerical results are in good agreement with those of the experimental data.

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