Search Results (6)

Multichannel graphite electrodes (MGrEs) have been designed and fabricated in this study. A template was cut from an adhesive plastic sheet using a desktop cutting device. The template was placed on a polypropylene substrate, and carbon graphite ink was applied with a squeegee to the template. The size of the auxiliary electrode (AE) as well as the location of the reference electrode (RE) of MGrEs design were investigated. Scanning electron microscopy was used to determine the thickness of the ink on the four working electrodes (WEs), which was 21.9 ± 1.8 µm. Cyclic voltammetry with a redox probe solution was used to assess the precision of the four WEs. The intra-electrode repeatability and inter-electrode reproducibility of the MGrEs production were satisfied by low RSD (<6%). Therefore, the MGrEs is reliable and capable of detecting four replicates of the target analyte in a single analysis. The electrochemical performance of four WEs was investigated and compared to one WE. The sensitivity of the MGrEs was comparable to the sensitivity of a single WE. The MGrEs’ potential applications were investigated by analyzing the nitrite in milk and tap water samples (recoveries values of 97.6 ± 0.4 to 110 ± 2%). Full article

The gold standard test for identifying SARS-CoV-2, the causative agent of COVID-19, is polymerase chain reaction (PCR). Despite their limited sensitivity, SARS-CoV-2 antigen rapid diagnostic tests are vital tools in the fight against viral spread. Owing to its simplicity and low cost, the lateral flow assay (LFA) is the most extensively used point-of-care diagnostic test. Here, we report a newly designed LFA-NanoSuit method (LNSM) that works in conjunction with desktop scanning electron microscopy (SEM) to detect SARS-CoV-2. LNSM requires no standard SEM treatment, avoids cellulose and residual buffer deformation, and enables the capture of high-resolution images of antibody-labeled gold/platinum particles reacting with SARS-CoV-2 antigens. To assess its applicability, we compared clinical SARS-CoV-2 samples via visual detection of LFA, LSNM detection of LFA, and real-time reverse transcription-PCR (qRT-PCR). Compared to qRT-PCR, LNSM showed 86.7% sensitivity (26/30; 95% confidence interval (CI): 69.28–96.24%) and 93.3% specificity (14/15; 95% CI: 68.05–99.83%) for SARS-CoV-2. In samples with a relatively low SARS-CoV-2 RNA copy number (30 < Ct ≤ 40), the sensitivity of LNSM was greater (73.3%) than that of visual detection (0%). A simple, sensitive, and quantitative LNSM can be used to diagnose SARS-CoV-2. Full article

3D printing is an emerging and disruptive technology, supporting the field of medicine over the past decades. In the recent years, the use of additive manufacturing (AM) has had a strong impact on everyday dental applications. Despite remarkable previous results from interdisciplinary research teams, there is no evidence or recommendation about the proper fabrication of handheld medical devices using desktop 3D printers. The aim of this study was to critically examine and compare the mechanical behavior of materials printed with FFF (fused filament fabrication) and CFR (continuous fiber reinforcement) additive manufacturing technologies, and to create and evaluate a massive and practically usable right upper molar forceps. Flexural and torsion fatigue tests, as well as Shore D measurements, were performed. The tensile strength was also measured in the case of the composite material. The flexural tests revealed the measured force values to have a linear correlation with the bending between the 10 mm (17.06 N at 5000th cycle) and 30 mm (37.99 N at 5000th cycle) deflection range. The findings were supported by scanning electron microscopy (SEM) images. Based on the results of the mechanical and structural tests, a dental forceps was designed, 3D printed using CFR technology, and validated by five dentists using a Likert scale. In addition, the vertical force of extraction was measured using a unique molar tooth model, where the reference test was carried out using a standard metal right upper molar forceps. Surprisingly, the tests revealed there to be no significant differences between the standard (84.80 N ± 16.96 N) and 3D-printed devices (70.30 N ± 4.41 N) in terms of extraction force in the tested range. The results also highlighted that desktop CFR technology is potentially suitable for the production of handheld medical devices that have to withstand high forces and perform load-bearing functions. Full article

Almost one-third of the revenues of the Additive Manufacturing (AM) machines market is generated by desktop systems. A new category of such devices are Laser Sintering (LS) machines, in which we can find a few representatives of this group. A growing interest in the use of desktop AM solutions in research and industry is visible, and therefore an evaluation of its capabilities and limitations is desirable. The presented paper focuses on comparing desktop (Sintratec S1; Sinterit Lisa) and industrial (Formiga P110) LS systems. The properties of raw materials were characterized by Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC), as well as by determining the Particle Size Distribution (PSD) and static and dynamic flowability of powder. Laser Sintering commercial sets were characterized by their mechanical properties (tensile strength), surface quality (roughness), as well as by their accuracy and porosity (computed tomography). The conducted test showed significant differences, especially in the case of material properties and manufacturing repeatability. The found differences between desktop and industrial LS systems suggest that the use of a low-budget LS system, especially for the research and production of end-use parts, has to take into account its limitations. Full article

Scanning electron microscopy has been developed for topographic analysis at the nanometer scale. Herein, we present a silicon p-n diode with multi-annular configuration to detect backscattering electrons (BSE) in a homemade desktop scanning electron microscope (SEM). The multi-annular configuration enables the enhancement of the topography contrast of 82.11 nA/μm as compared with the commercial multi-fan-shaped BSE detector of 40.08 nA/μm. Additionally, we integrated it with lateral p-n junction processing and aluminum grid structure to increase the sensitivity and efficiency of the multi-annular BSE detector that gives higher sensitivity of atomic number contrast and better surface topography contrast of BSE images for low-energy detection. The responsivity data also shows that MA-AL and MA p-n detectors have higher gain value than the MA detector does. The standard deviation of measurements is no higher than 1%. These results verify that MA p-n and MA-AL detectors are stable and can function well in SEM for low-energy applications. It is demonstrated that the multi-annular (MA) detectors are well suited for imaging in SEM systems. Full article

The current paper studies the influence of geometrical parameters of the fused deposition modeling (FDM)—fused filament fabrication (FFF) 3D printing process on printed part strength for open source desktop 3D printers and the most popular material used for that purpose—i.e., polylactic acid (PLA). The study was conducted using a set of different nozzles (0.4, 0.6, and 0.8 mm) and a range of layer heights from the minimum to maximum physical limits of the machine. To assess print strength, a novel assessment method is proposed. A tubular sample is loaded in the weakest direction (across layers) in a three-point bending fixture. Mesostructure evaluation through scanning electronic microscopy (SEM) scans of the samples was used to explain the obtained results. We detected a significant influence of geometric process parameters on sample mesostructure, and consequently, on sample strength. Full article