Thermomechanical Performance of the Offset Crankshaft Heat Engine Driven by TiNiCu Shape Memory Alloys

Geothermal hot springs are among the alternative clean energy sources to the fossil fuels for mitigating the current global warming crisis. However, the accessible geothermal water at the surface was mostly at low temperature, which impairs the practicality of harvesting these energy. Shape memory alloys (SMAs), which deform through the increased temperature, were adapted into the rotating mechanism as the actuators with the aims to convert the low-temperature heat into the mechanical work. This study utilized the helical spring-shaped TiNiCu SMAs as the actuators for the offset crankshaft heat engine. Performance of this engine was evaluated using rope brake dynamometer, by which the rotational speed, torque, and power were measured at the water temperature from 55-85°C. The results show that the engine performance increased with increasing water temperature and was dependent on the crankshaft arrangement. The offset angle of 30° was found to be optimal in this study with maximum torque of more than 5.8 N∙m and maximum power of 3.9 W at 15.7 rpm when operating at water temperature of 85°C. This study shows that the heat engine driven by TiNiCu SMAs could harvest low-temperature energy from the geothermal hot springs with the maximum observable efficiency of around 1.4%

Changes in the extracellular microenvironment and osteogenic responses of mesenchymal stem/stromal cells induced by in vitro direct electrical stimulation

Electrical stimulation (ES) has potential to be an effective tool for bone injury treatment in clinics. However, the therapeutic mechanism associated with ES is still being discussed. This study aims to investigate the initial mechanism of action by characterising the physical and chemical changes in the extracellular environment during ES and correlate them with the responses of mesenchymal stem/stromal cells (MSCs). Computational modelling was used to estimate the electrical potentials relative to the cathode and the current density across the cell monolayer. We showed expression of phosphorylated ERK1/2, c-FOS, c-JUN, and SPP1 mRNAs, as well as the increased metabolic activities of MSCs at different time points. Moreover, the average of 2.5 μM of HO and 34 μg/L of dissolved Pt were measured from the electrically stimulated media (ES media), which also corresponded with the increases in SPP1 mRNA expression and cell metabolic activities. The addition of sodium pyruvate to the ES media as an antioxidant did not alter the SPP1 mRNA expression, but eliminated an increase in cell metabolic activities induced by ES media treatment. These findings suggest that HO was influencing cell metabolic activity, whereas SPP1 mRNA expression was regulated by other faradic by-products. This study reveals how different electrical stimulation regime alters cellular regenerative responses and the roles of faradic by-products, that might be used as a physical tool to guide and control cell behaviour.BBSRC grant (BB/M013545/1). It also receives funding from The Royal Thai Government Scholarship (ST 4729) and Rosetrees Trust (M48

Electroactive 3D printed scaffolds based on percolated composites of polycaprolactone with thermally reduced graphene oxide for antibacterial and tissue engineering applications

Applying electrical stimulation (ES) could affect different cellular mechanisms, thereby producing a bactericidal effect and an increase in human cell viability. Despite its relevance, this bioelectric effect has been barely reported in percolated conductive biopolymers. In this context, electroactive polycaprolactone (PCL) scaffolds with conductive Thermally Reduced Graphene Oxide (TrGO) nanoparticles were obtained by a 3D printing method. Under direct current (DC) along the percolated scaffolds, a strong antibacterial effect was observed, which completely eradicated S. aureus on the surface of scaffolds. Notably, the same ES regime also produced a four-fold increase in the viability of human mesenchymal stem cells attached to the 3D conductive PCL/TrGO scaffold compared with the pure PCL scaffold. These results have widened the design of novel electroactive composite polymers that could both eliminate the bacteria adhered to the scaffold and increase human cell viability, which have great potential in tissue engineering applications.CONICYT-PCHA/Doctorado 21150921 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1150130 Project Millennium Nuclei in Soft Smart Mechanical Metamaterials, Santiago, Chil