Microfluidic devices have evolved into low-cost, simple, and powerful analytical tool platforms. Herein, an electrochemically-based microfluidic nanobiosensor array for monoplex and multiplex detection of physiologically relevant analytes is reviewed. Unlike other analyte detection methods, microfluidics-based embedded electrochemical nanobiosensors are portable, custom electrochemical readers for signal reading. Microfluidic devices and electrochemical sensors can be integrated into monoplex or multiplex systems. The integrated system is simple to use and sensitive, and so has great potential as a powerful tool for profiling immune-mediated treatment responses in real time. It may also be developed further as a point-of-care diagnostic device for conducting near-patient tests using biological samples. Therefore, using mutiplex analysis, a biosensor array may detect multiple analytes in a sample solution and provide different outputs for each analyte. A microfluidic electrochemical nanobiosensor, for example, can detect urine glucose, lactate, and uric acid. The microfluidic array of integrated nanobiosensors and electrochemical sensors enables fast and cost-effective selection of high-quality and statistically significant diagnostic data at the point of care. The multiplex analytical test is an important molecular tool for academic research as well as clinical diagnosis. Although key approaches for analysing numerous analytes have been developed, none of them are suitable for point-of-care diagnostics, especially in situations with limited resources. In this study, monoplex and multiplex microfluidic assays for rapid measurement of single and multiple analytes at the point of care are presented. Since this test can analyse both single and multiple analytes, it is exceptionally specific, easy to use, and inexpensive. The ability of integrated electrochemical-based microfluidic devices with single channel and multiple channels systems to perform monoplex and multiplex analysis simultaneously and independently is the novelty of this review. 

Integration of microfluidic channel on electrochemical-based nanobiosensors for monoplex and multiplex analyses: An overview

Silicon inverted pyramids have been shown to exhibit superior SERS properties compared to ortho-pyramids, yet low-cost, simple preparation processes are lacking at present. This study demonstrates a simple method, silver-assisted chemical etching combined with PVP, to construct silicon inverted pyramids with a uniform size distribution. Two types of Si substrates for surface-enhanced Raman spectroscopy (SERS) were prepared via silver nanoparticles deposited on the silicon inverted pyramids by electroless deposition and radiofrequency sputtering, respectively. The experiments were conducted using rhodamine 6G (R6G), methylene blue (MB) and amoxicillin (AMX) molecules to test the SERS properties of the Si substrates with inverted pyramids. The results indicate that the SERS substrates show high sensitivity to detect the above molecules. In particular, the sensitivity and reproducibility of the SERS substrates with a denser silver nanoparticle distribution, prepared by radiofrequency sputtering, are significantly higher than those of the electroless deposited substrates to detect R6G molecules. This study sheds light on a potential low-cost and stable method for preparing silicon inverted pyramids, which is expected to replace the costly commercial Klarite SERS substrates.

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A Simple Method for the Fabrication of Silicon Inverted Pyramid Substrates for Surface-Enhanced Raman Spectroscopy

The design of carbon material-based heterojunction solar cells (HJSCs) provides a promising approach to convert and collect solar energy. With unique photonic, electronic and mechanical properties, versatile carbon materials have attracted considerable attention in the design of heterojunction structures because of the multi-functional applications of carbon materials in the booming field of photovoltaics (PVs). Significant effort has been devoted to enhancing the light absorption capacity and charge/carrier transporting ability to obtain state-of-the-art HJSCs. This review presents the basic application of various carbon materials for PVs and the basic principles of carbon materials in HJSCs. Several optimisation methods for carbon nanotube (CNT) film modification and cell performance, such as optical property and Fermi level tuning, as well as morphological design and interface engineering, are highlighted in a summary of the state-of-art progress of CNT-based HJSCs. Moreover, the representative applications of carbon materials based flexible HJSCs are discussed. Finally, promising pathways and prospects of CNTs in HJSCs and their advanced devices are proposed using film modification, mechanism modulation, and device design to achieve cost-effective, high-performance, and flexible solar cells (SCs). 

Insights into the application of carbon materials in heterojunction solar cells

Inverted pyramid-texturing of silicon surface has been proven to have great application potential in silicon solar cells. In this paper, we utilized Ag-assisted chemical etching (Ag–ACE) technology combing with polyvinylpyrrolidone (PVP) to fabricate an inverted pyramid textured Si surface. We call it Ag@PVP–ACE. The effect of different experimental parameters on etching results was observed. We show that the microstructure of the Si surface exhibited two states as the concentration of NH4HF2 and PVP concentration changed: polishing and inverted pyramid texturing. Meanwhile, we found inverted pyramids easier to form at the high temperature and low H2O2 concentration of the etching system. Consequently, compared to inverted pyramid structures fabricated by nanostructure rebuilding (NSR) technology and Ag@PVP–ACE, we consider that Ag@PVP–ACE technology could become a viable strategy for fabricating inverted pyramid textured Si wafers in Si solar cells production.

https://www.mdpi.com/2073-4352/11/5/459/pdf

One-Step Fabrication of Inverted Pyramid Textured Silicon Wafers via Silver-Assisted Chemical Etching Combing with Synergism of Polyvinylpyrrolidone (PVP)

Zisheng Guan

Papers

One-Step Fabrication of Inverted Pyramid Textured Silicon Wafers via Silver-Assisted Chemical Etching Combing with Synergism of Polyvinylpyrrolidone (PVP)