Hydrogels exhibit excellent moldability, biodegradability, biocompatibility, and extracellular matrix-like properties, which make them widely used in biomedical fields. Because of their unique three-dimensional crosslinked hydrophilic networks, hydrogels can encapsulate various materials, such as small molecules, polymers, and particles; this has become a hot research topic in the antibacterial field. The surface modification of biomaterials by using antibacterial hydrogels as coatings contributes to the biomaterial activity and offers wide prospects for development. A variety of surface chemical strategies have been developed to bind hydrogels to the substrate surface stably. We first introduce the preparation method for antibacterial coatings in this review, which includes surface-initiated graft crosslinking polymerization, anchoring the hydrogel coating to the substrate surface, and the LbL self-assembly technique to coat crosslinked hydrogels. Then, we summarize the applications of hydrogel coating in the biomedical antibacterial field. Hydrogel itself has certain antibacterial properties, but the antibacterial effect is not sufficient. In recent research, in order to optimize its antibacterial performance, the following three antibacterial strategies are mainly adopted: bacterial repellent and inhibition, contact surface killing of bacteria, and release of antibacterial agents. We systematically introduce the antibacterial mechanism of each strategy. The review aims to provide reference for the further development and application of hydrogel coatings.
The acceleration sensor with high g value is widely used in a variety of fields, including collision impact, aerospace, and defense security and thus is a key focus in the future. The sensor with a double-ended four-beam structure is investigated in this paper via finite element simulation analysis. The measurement sensitivity of the sensor can be improved by changing the position of the cantilever beam. Furthermore, transverse interference in the X-direction and Y-direction can be eliminated in theory through the layout of piezoresistors and the Wheatstone circuit. The simulation results show that the sensor's sensitivity is 2.6μV/g while its cross-sensitivity in the X-direction and Y-direction is 0%, indicating that the sensor's performance has been substantially improved.
In the process of screw thread manufacturing, the cooling liquid or lubricating oil will adhere to the screw thread surface, which affects the vision measurement results of the screw thread parameters. To simulate the adhesion behavior of oil on the thread surface during the actual measurement, four different attachment states were set in this experiment. An image measuring instrument was used to collect the screw thread images of different adhesion states. Then, the distribution of the oil film on the screw thread surface was analyzed with computer image processing. The visual inspection method was used to obtain the relative influence rate of the oil adhesion on the measurement result of the screw thread parameters. Finally, an experiment-based pitch diameter compensation method was proposed, and the compensation effect of this method was verified with the test method. Experiments showed that the effect of oil adhesion on the measurement results of the diameter parameters is greater than 7 µm, and the effect on the measurement result of the thread angle is greater than 0.1°. The compensation experiment showed that the compensation efficiency was above 70% for the pitch diameter.
Aiming at the problems of low efficiency of the traditional method for detecting smooth plug gauges and poor repeat accuracy of measurement parameters, a measuring system for the diameter of a smooth plug gauge based on machine vision technology is designed. This system drives the work-piece to move by two-dimensional work platform and collects image data through CCD, and the diameter parameters of the smooth plug gauge are obtained by processing the image which uses the threshold neighborhood location and segmentation method. In this paper, the mechanical structure and control structure of the measuring system are designed, the measurement principle and calibration method are explained, the relationship between the diaphragm and the threshold value under a fixed light intensity, and the relationship between the light intensity and the threshold value under a fixed diaphragm are studied. Finally, experiments have verified that the measuring system can complete the measurement efficiently, automatically, and with high precision within 20 s, and the repeatability of the measurement does not exceed 1 μm.
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