Ground reaction force (GRF) is a significant factor for the evaluation of animal locomotion. Recently, micro force plates have been implemented as the GRF measurement method for tiny insects. Previous micro force plates were highly sensitive but fragile and laborious to fabricate because of the use of strain-sensing elements. Here, we applied high-resolution 3D printing and a noncontact displacement meter to a micro force plate for a fruit fly. A force plate structure with 3D supporting microsprings is fabricated with easy and reproducible micro 3D printing, enabling both high sensitivity and toughness. By detecting the displacement of the plate centre externally, the vertical GRF when a fruit fly lands on the plate surface is calculated via the spring constant as the whole device. The spring constant of the microspring is designed to be approximately 5.98 N/m so that a high-resolution external laser displacement meter realizes a force resolution less than 1/50 of the body weight of a fruit fly. Providing that the four springs have the same spring constant and the displacement meter aligns at the plate centre, there is no positional error when converting from displacement to force in principle. However, the fabrication error leads to the spring constant difference. Here, we theoretically and experimentally determined the measurement point of the distance sensor where the positional error caused by the difference in spring constant of the four microsprings is compensated. It was confirmed that the calibration process improved the position error to be within ±1.5% in the experiment. Finally, we demonstrated the GRF measurement of a fruit fly. The average GRF was 6.5 μN, which was equal to the weight of a fruit fly. Our proposed device can help evaluate the biomechanics of tiny insects.
Transcranial magnetic stimulation is a painless and noninvasive method for treating brain disorders. The coil-geometries that match the head topologies achieve more effective stimulation, however it is difficult for a rigid coil to fit the skulls of all patients. We propose and develop a rubber-like flexible coil that can be shaped into different geometries to reduce the inter-individual variabilities in its clinical use. The main challenge is attributed to the fact that the external bending and induced Lorentzian forces cause coil deformation and fatigue. Herein, we investigated the influence of bending on the electromagnetic characteristics of the flexible coil. The magnetic field distribution was calculated and measured using a search coil. The induced Lorentzian force was calculated and the induced eddy current density was simulated using the scalar potential finite difference (SPFD) method. For a mechanical characterization, we fixed the center of the coil, and external bending forces were applied on the two wings of the coils, while Lorentzian forces were applied in a direction normal to the side wall of the wire groove. Fatigue analyses of these forces were also conducted. The results show that the eddy current density induced in the brain by the flexible coil was significantly higher compared to that of the figure-eight and butterfly coils. Fatigue analyses show that the bending force required to achieve a close coil fit on the human head and the generated Lorentzian force would not lead to fatigue problem.
The new coronavirus infection (COVID-19) has spread to numerous countries around the world since several cases of the disease were first reported in late December 2019 in China. Currently, the WHO strongly recommends infection prevention measures such as wearing masks, hand washing, and frequent disinfection of high-touch surfaces, but there were many arguments against infection prevention policy in March 2020. For example, the WHO did not recommend the use of masks for the healthy general public. In Japan, wearing a mask was required before the habit of wearing a mask was established, which gave additional works of checking whether customer was wearing a mask to the employees. To reduce the workloads of employee and ensure mask-wearing, we started providing the mask-wearing system free of charge on March 5, 2020. We also developed hand washing time estimation and disinfection support system. It is useful to accumulate data on the status of implementation of countermeasures by our application, which leads to gain useful knowledge regarding countermeasures against COVID-19 as well as other infectious diseases. In this paper, we describe the development and introduction impacts of these systems in a pandemic emergencies. In addition, because of the security and privacy issues in running these image analysis applications, we discuss the delivery methods suitable for each service.
This paper reports on a force plate (FP) using mechanical springs and noncontact distance sensors. The ground reaction force (GRF) is one of the factors for clarify biomechanics, and FPs are widely used to measure it. The sensor elements of conventional FPs are mainly strain gauges. Thus, the mechanical properties of FP depend on the sensor element performance. If the FP performance must change, we must redesign the FP, including changing the sensor elements. Here, we proposed an FP that uses a measuring principle based on simple springs and noncontact sensors. The shape and performance of the proposed FP are expected to change easily. As a prototype device, we designed and fabricated an FP installed with 12 springs and four sensors for human walking. A planar coil and magnet were used as the sensor elements, and the sensor output was proportional to the vertical and horizontal displacements. The FP resonance frequency was 123 Hz, which was larger than the required specification. The calibration experiments showed that vertical and horizontal forces and moments could be measured independently. The FP’s resolutions were 1.9 N and 1.4 N in the anterior–posterior and vertical directions, respectively. Furthermore, the fabricated FP measured GRF similarly to the commercial FP when a human walked on the plate. These results suggest that the proposed method will be helpful for FPs with custom-made requirements.
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