# Development of an Ergonomic Writing Assistive Device for Finger Pain Reduction in the Elderly
## 4 Discussion
The NDWAD is made of soft TPU, so it disperses pressure, but SW and WB are all hard, so pressure cannot be dispersed. We also hypothesize that the shape of the NDWAD, which was designed for the flexion of the hand, helped distribute and reduce pressure. The NDWAD showed similar values to SW in muscle activity, but the thumb and index finger pressures were significantly lower than SW. It can be concluded that the NDWAD is better than SW in terms of finger pressure reduction. It is clear that the muscle activity results are highly correlated with the grip method of WADs, but the finger pressure results are highly correlated with the material (hardness) and shape of the WAD, as opposed to grip method. Existing WADs are not finger-tailored, and as only a single size is manufactured, it was not possible to provide customized sizes suited to use by both male and female participants. In the experiment, as only the NDWAD provided two sizes considering the size of the finger (male and female), it can be determined that not only the physical properties of each WAD but also the size factor helped reduce the pressure. The NDWAD, developed through a 3D printer, could provide customized WADs, but for the smooth progress of the experiment, the experiment was conducted using only women's S and men's M sizes. Considering that personalized assistive devices manufactured with a 3D printer have shown positive effects in previous studies [27, 28, 29, 30], further finger pressure reductions are to be expected if personalized NDWADs are used in the experiment. As shown in the radar chart in Figure 7, the NDWAD showed the highest satisfaction in all items, followed by SW and WB. There were significant differences in the 'Easy to use', 'Comfort', 'Effectiveness', 'Use again', and 'Recommendation' assessments. Differences in 'Dimension', 'Weight', 'Safety', and 'Durability' were not significant. In terms of 'Dimension' satisfaction, as only one size was produced for SW and WB, we expected that the NDWAD, which provided two sizes, would show a statistically significantly higher satisfaction level. Ultimately, however, we found that the difference in dimension satisfaction was insignificant. This is because, unlike the NDWAD, where the position of the fingers is fixed to some extent considering the curvature of the fingers, SW and WB do not have detailed positions, so they can be used even if the size does not match. In terms of 'Weight' satisfaction, NDWAD and SW were particularly similar, while WB showed relatively low satisfaction. During the experiment, users seemed to highly appreciate the lightness of NDWAD and SW, as opposed to the heaviness of WB. Nevertheless, the reason there is no significant difference is that the shape of the WB (large area in contact with the paper) can disperse the weight, so the weight burden may have been low, except when the user changes paper. The reason for the insignificant differences in results across the 'Safety' and 'Durability' assessments seems to be that each WAD has a relatively simple shape or structure and is made of materials that are not easily destroyed or threatened. The WB, with its unfamiliar grip method, received a low satisfaction score in the 'Easy to use' item, while SW and NDWAD, which used relatively familiar dynamic-tripod grips, received higher scores. In terms of 'Comfort' satisfaction, the relatively hard and heavy WB received the lowest score. The hard but light SW received the second highest satisfaction score, and the soft and light NDWAD received the highest. It is likely that factors such as material and weight are reflected in the evaluation score. The results of the 'Effectiveness' item appear to have changed depending on the presence or absence of ergonomic design. The ergonomic design considering the shape and curvature of the hand, the two sizes provided depending on the size of the hand, and the frictional properties of the TPU used as a material allowed the participants to grip the NDWAD well.