With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As a core member within the wearable electronics family, flexible strain sensors play an essential role in the structure design and functional optimization. To further enhance the stretchability, flexibility, sensitivity, and electricity performances of the flexible strain sensors, enormous efforts have been done covering the materials design, manufacturing approaches and various applications. Thus, this review summarizes the latest advances in flexible strain sensors over recent years from the material, application, and manufacturing strategies. Firstly, the critical parameters measuring the performances of flexible strain sensors and materials development contains different flexible substrates, new nano- and hybrid- materials are introduced. Then, the developed working mechanisms, theoretical analysis, and computational simulation are presented. Next, based on different material design, diverse applications including human motion detection and health monitoring, soft robotics and human-machine interface, implantable devices, and biomedical applications are highlighted. Finally, synthesis consideration of the massive production industry of flexible strain sensors in the future; different fabrication approaches that are fully expected are classified and discussed.

Several models on the circadian effect have been applied to indoor circadian lighting design, but applications in road lighting have not yet been clarified. Based on existing models and circadian research, we examined equivalent melanopic lux (EML), circadian light (CL_A), and circadian stimulus (CS) representing the circadian effect and the S/P ratio representing the mesopic vision effect, among a dataset of light sources at photopic adaptation illuminance values of 1, 3, 10, 30, and 100 lx. The results show that the S/P ratio correlates with EML and CS (or CL_A) much stronger than it correlates with color temperature. The EMLs of light sources are below 50 EML in mesopic vision, and the CSs of most light sources are below or around the threshold value of 0.05. We conclude that the circadian effect is not a significant issue in mesopic vision under most conditions and that optimization for mesopic efficiency is still a good strategy. There are quite a few light sources that may achieve both ideal mesopic efficiency and low CS. This work clarifies the circadian effect and mesopic vision effect performance of light sources in mesopic vision and will help guide choosing suitable light sources and optimization strategies for road lighting.

The anterolateral motor cortex of rodents is an important motor auxiliary area, and its function is similar to that of the premotor area in humans. Activation and inhibition of the contralesional anterolateral motor cortex (cALM) have been shown to have direct effects on motor behavior. However, the significance of cALM activation and inhibition in the treatment of stroke remains unclear. This study investigated the role of optogenetic cALM stimulation in a mouse model of cerebral stroke. The results showed that 21-day optogenetic cALM inhibition, but not activation, improved neurological function. In addition, optogenetic cALM stimulation substantially altered dendritic structural reorganization and dendritic spine plasticity, as optogenetic cALM inhibition resulted in increased dendritic length, number of dendritic spines, and number of perforated synapses, whereas optogenetic activation led to an increase in the number of multiple synapse boutons and the number of dendritic intersections. Furthermore, RNA-seq analysis showed that multiple biological processes regulated by the cALM were upregulated immediately after optogenetic cALM inhibition, and that several immediate-early genes (including cFOS, Erg1, and Sema3f) were expressed at higher levels after optogenetic inhibition than after optogenetic activation. These results were confirmed by quantitative reverse transcription-polymerase chain reaction. Finally, immunofluorescence analysis showed that the c-FOS signal in layer V of the primary motor cortex in the ischemic hemisphere was higher after optogenetic cALM activation than it was after optogenetic cALM inhibition. Taken together, these findings suggest that optogenetic cALM stimulation promotes neural reorganization in the primary motor cortex of the ischemic hemisphere, and that optogenetic cALM inhibition and activation have different effects on neural plasticity. The study was approved by the Experimental Animal Ethics Committee of Fudan University (approval No. 201802173S) on March 3, 2018.