Emerging wearable and implantable biomedical energy harvesting devices demand efficient power conversion, flexible structures, and lightweight construction. This paper presents Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) micro-porous structures, which can be tuned to specific mechanical flexibilities and optimized for piezoelectric power conversion. Specifically, the water vapor phase separation method was developed to control microstructure formation, pore diameter, porosity, and mechanical flexibility. Furthermore, we investigated the effects of the piezoelectric layer to supporting layer Young's modulus ratio, through using both analytical calculation and experimentation. Both structure flexibility and stress-induced voltage were considered in the analyses. Specification of electromechanical coupling efficiency, made possible by carefully designed three-dimensional porous structures, was shown to increase the power output by five-fold relative to uncoupled structures. Therefore, flexible PVDF-TrFE films with tunable microstructures, paired with substrates of different rigidities, provide highly efficient designs of compact piezoelectric energy generating devices.

Rapid screening of biomarkers, with high specificity and accuracy, is critical for many point-of-care diagnostics. Microfluidics, the use of microscale channels to manipulate small liquid samples and carry reactions in parallel, offers tremendous opportunities to address fundamental questions in biology and provide a fast growing set of clinical tools for medicine. Emerging multi-dimensional nanostructures, when coupled with microfluidics, enable effective and efficient screening with high specificity and sensitivity, both of which are important aspects of biological detection systems. In this review, we provide an overview of current research and technologies that utilize nanostructures to facilitate biological separation in microfluidic channels. Various important physical parameters and theoretical equations that characterize and govern flow in nanostructure-integrated microfluidic channels will be introduced and discussed. The application of multi-dimensional nanostructures, including nanoparticles, nanopillars, and nanoporous layers, integrated with microfluidic channels in molecular and cellular separation will also be reviewed. Finally, we will close with insights on the future of nanostructure-integrated microfluidic platforms and their role in biological and biomedical applications.

Covalent organic framework (COF) nanosheets prepared from the direct intercalation reaction between melamine and g-C3N4 are reported for the first time. Scanning electron microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy are applied to characterize the novel COF nanosheets. It is observed apparently from the TEM image that COF nanosheets are obtained. Successful preparation of COF nanosheets is proved further by vanishment of the typical diffraction peak of COFs in the XRD pattern and the appearance of quadrant and semicircle stretching of the s-triazine ring at 1568 and 1469 cm−1 in the FTIR spectra of COF nanosheets. The prepared COF nanosheets are used as a flame retardant for the cable sheath material. The thermal stability, thermal shrinkage, oxygen index, and vertical combustion are tested. The research results show that the COF nanosheet flame retardant increases the thermal stability time of the sheath material from 89 to 125 min, and the thermal shrinkage rate is reduced to 2.17%. The oxygen index and vertical combustion tests show that the COF nanosheet flame retardant makes the oxygen index of the cable sheath material reach 29.5, and the flame retardant grade reaches UL-94 V-0. From the scanning electron microscopy analysis of the carbon residue of the cable sheath material after burning, it is found that the COF nanosheet flame retardant changes the shape of the carbon layer of the cable sheath material into a dense honeycomb structure, which prevents the diffusion of oxygen and combustible gases, thereby inhibiting the transmission of flame and heat and effectively improving the flame retardancy of the cable sheath material.