Silicon-Based Integrated Label-Free Optofluidic Biosensors: Latest Advances and Roadmap

By virtue of the well-developed micro- and nanofabrication technologies and rapidly progressing surface functionalization strategies, silicon-based devices have been widely recognized as a highly promising platform for the next-generation lab-on-a-chip bioanalytical systems with a great potential for point-of-care medical diagnostics. Herein, an overview of the latest advances in silicon-based integrated optofluidic label-free biosensing technologies relying on the efficient interactions between the evanescent light field at the functionalized surface and specifically bound analytes is presented. State-of-the-art technologies demonstrating label-free evanescent wave-based biomarker detection mainly encompass three device configurations, including on-chip waveguide-based interferometers, microring resonators, and photonic-crystal-based cavities. Moreover, up-to-date strategies for elevating the sensitivities and also simplifying the sensing processes are discussed. Emerging laboratory prototypes with advanced integration and packaging schemes incorporating automatic microfluidic components or on-chip optoelectronic devices lead to one significant step forward in real applications of decentralized diagnostics. Besides, particular attention is paid to currently commercialized label-free optical bioanalytical models on the market. Finally, the prospects are elaborated with several research routes toward chip-scale, low-cost, highly sensitive, multi-functional, and user-friendly bioanalytical systems benefiting to global healthcare. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

THE INFLUENCE OF NANOCELLULOSE AND SILICON DIOXIDE ON THE MECHANICAL PROPERTIES OF THE CELL WALL WITH RELATION TO THE BOND INTERFACE BETWEEN WOOD AND UREA-FORMALDEHYDE RESIN

Urea-formaldehyde (UF) resin is used as an adhesive in the most wood-based composite plants in China. The quality of such composites is strongly affected by the mechanical properties of the cell wall in relation to the interface between UF resin and wood. This research investigates the mechanical properties of the cell wall in the bond interface of wood and UF resin with nanocellulose and silicon dioxide, and compares the mechanical properties of wood-adhesive interface cell walls to their gluing strength. The hardness and reduced modulus of the cell wall were investigated by means of nanoindentation. The test results show that there was a close relationship between the mechanical properties of the cell walls at the wood-adhesive interface and the percentage of nanocellulose or SiO2 in the UF. The shear strength of UF resin with nanofibrillated cellulose (NFC) or nano-SiO2 in bonded wood also gradually increased when the content of these two kinds of nanomaterials was increased from 0% to 2%

Fast-Response Micro-Phototransistor Based on MoS2/Organic Molecule Heterojunction

Over the past years, molybdenum disulfide (MoS2) has been the most extensively studied two-dimensional (2D) semiconductormaterial. With unique electrical and optical properties, 2DMoS2 is considered to be a promising candidate for future nanoscale electronic and optoelectronic devices. However, charge trapping leads to a persistent photoconductance (PPC), hindering its use for optoelectronic applications. To overcome these drawbacks and improve the optoelectronic performance, organic semiconductors (OSCs) are selected to passivate surface defects, tune the optical characteristics, and modify the doping polarity of 2D MoS2. Here, we demonstrate a fast photoresponse in multilayer (ML) MoS2 by addressing a heterojunction interface with vanadylphthalocyanine (VOPc) molecules. The MoS2/VOPc van der Waals interaction that has been established encourages the PPC effect in MoS2 by rapidly segregating photo-generated holes, which move away from the traps of MoS2 toward the VOPc molecules. The MoS2/VOPc phototransistor exhibits a fast photo response of less than 15 ms for decay and rise, which is enhanced by 3ordersof magnitude in comparison to that of a pristine MoS2-based phototransistor (seconds to tens of seconds). This work offers a means to realize high-performance transition metal dichalcogenide (TMD)-based photodetection with a fast response speed