In this study, the shape and thermal effects of metal films on the stress-induced bending of micromachined bilayer cantilever are systematically investigated. The cantilever makes use of residual stresses in thin films to induce the bending of microstructures by applying preloads. The characterization of the bilayer cantilever with different Au distribution has been performed to observe out-of-plane deformation. A finite-element model has been established to analyze such a deformation using experimental and theoretical results. It indicates that the commonly used formula for predicting the deformation of the cantilever is not valid for these devices. When the percentage of the area deposited with a metal is increased, deflection angle also increases. Furthermore, the influence of postprocessing temperature on the residual stress of the metal films is examined. Postprocessing temperature and residual stress reveal a close relationship. As postprocessing temperature increases, the residual stress of the metal increases, resulting in a larger out-of-plane deformation of the cantilever. Residual stress increases to a saturation value while the temperature reaches a critical value. This new finding could greatly affect the performance of a stress-induced bilayer cantilever. Finally, a switchable micromachined corner mirror is demonstrated using the bilayer cantilever.
To increase the productivity of injection molding machines, we developed a smart injection part weight stability control system based on Cþþ programming and domain knowledge. The proposed system is meant to eliminate variability in the quality of injected parts by adjusting the changeover position. We developed a viscosity index based on melt pressure data related to guide the adjustment to the changeover position in accordance with material properties. This was achieved by mounting a pressure sensor on the nozzle of the injection molding machine to enable the on-line monitoring of pressure throughout the injection molding process. A series of experiments was conducted to characterize the relationship between viscosity index and injection-molded samples in order to validate the efficacy of the proposed injection stability system. Single-factor experiments were conducted with the changeover position and melt temperature as parameters. The quality of the molded samples obtained under different process parameters was evaluated in terms of weight. Experiment results revealed a correlation between changes in viscosity index and changes in the weight of the samples. The injection stability system can also be operated in self-adjusting mode, in which the changeover position is varied according to viscosity index. In experiments, abnormal machine operations prompted the adjustment of changeover position. Variation in the weight of parts was used to define an index to validate the efficacy of the proposed system.
This paper reports a new micromachined, circulating, polymerase chain reaction (PCR) chip for nucleic acid amplification. The PCR chip is comprised of a microthermal control module and a polydimethylsiloxane (PDMS)-based microfluidic control module. The microthermal control modules are formed with three individual heating and temperature-sensing sections, each modulating a specific set temperature for denaturation, annealing and extension processes, respectively. Micro-pneumatic valves and multiple-membrane activations are used to form the microfluidic control module to transport sample fluids through three reaction regions. Compared with other PCR chips, the new chip is more compact in size, requires less time for heating and cooling processes, and has the capability to randomly adjust time ratios and cycle numbers depending on the PCR process. Experimental results showed that detection genes for two pathogens, Streptococcus pyogenes (S. pyogenes, 777 bps) and Streptococcus pneumoniae (S. pneumoniae, 273 bps), can be successfully amplified using the new circulating PCR chip. The minimum number of thermal cycles to amplify the DNA-based S. pyogenes for slab gel electrophoresis is 20 cycles with an initial concentration of 42.5 pg µl−1. Experimental data also revealed that a high reproducibility up to 98% could be achieved if the initial template concentration of the S. pyogenes was higher than 4 pg µl−1.
In this study, we developed a new fabrication process for a micromachined probe. The microprobe comprised a microcantilever, a nanotip and a supporting substrate, which are monolithically made of single-crystal silicon. The fabrication process started with a bilayer silicon wafer made up of a 20-µm-thick epitaxial Si layer with strong boron doping and a 400-µm-thick bulk Si substrate. The tip with a radius of curvature of 50 nm was formed by anisotropic etching followed by oxidation sharpening. Then a cantilever beam was released by the back etching of an etch-stop Si layer. The spring constants of cantilevers ranging from 0.03 to 0.4 N/m were determined by finite element analysis (FEA), static measurement using an atomic force microscope (AFM) system and dynamic measurement using a laser Doppler vibrometer (LDV) system. Most importantly, Young's modulus of thin-film materials could be confirmed using these methods. The developed probe was also equipped with a Pt heater to apply it to thermal machining on poly(methyl methacrylate) (PMMA) substrates. The cantilever tip was heated to above 120°C, and the successful machining of a cavity and a submicron-scale straight line was demonstrated. The development of the probes could be crucial for the submicron-scale machining of plastic materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.