Smartphone form factors: Effects of width and bottom bezel on touch performance, workload, and physical demand

Investigating the Use of Changes in Facial Features as Indicators of Physical Workload

OCCUPATIONAL APPLICATIONSPhysical workload may lead to negative outcomes, including musculoskeletal disorders. In this study, we found that there were observable changes in facial features over the length of a low intensity, prolonged assembly task, and that these changes were correlated to other measures of physical workload. This method can be implemented by practitioners to evaluate physical workload.

Development of an ergonomic design process for smartphone hard key locations

Smartphone hard key locations need to be ergonomically determined to improve grip stability and operational efficiency for users' convenience. The present study proposed an ergonomic design process that determines smartphone hard key locations by statistically analyzing the preferred hard key control areas of users with various hand sizes based on users' preferred grip postures and hard key control areas. The proposed design process analyzes the characteristics of product design, user, task, and use context, the types of preferred grip posture, the preference distribution of grip posture, and the preference distribution of hard-key area, and then recommends the locations of hard keys by considering the preference distribution of hard-key area and design constraints. The proposed design process was applied to a smartphone with a 5-inch screen, resulting in 77-96 mm from the bottom of the device for a volume key to 20 mm on the left side and 88-97 mm for a power key to 10 mm on the right side. The proposed design process for the determination of smartphone hard-key locations would be of use to determine the locations of various portable product interfaces.

Effects of Smartphone Size and Hand Size on Grip Posture in One-Handed Hard Key Operations

Greater understanding of the grip postures preferred by users is needed for the ergonomic design of smartphone user interfaces. The present study identifies user-preferred grip postures by smartphone size and hand size in one-handed hard key operations. Grip postures of 45 participants were photographed while major smartphone tasks were simulated in standing with smartphone mockups of nine screen sizes (3.0″–7.0″). The grip postures were encoded by the locations (left side: L, right side: R, top: T, bottom: B, front: F, back: K) of a smartphone and the number of fingers at each contact location. Three grip postures (L3-R1-K1: 70.0%, L4-R1: 13.3%, L3-R1-T1: 12.0%) were found dominant and the distribution of grip posture changed by smartphone size and hand size—the larger the smartphone size or hand size, the higher the frequency of L3-R1-K1. The grip posture frequency distribution by smartphone size would be of use to determine the optimal locations of hard keys on a smartphone of a particular size.

Understanding the Relationship between User’s Subjective Feeling and the Degree of Side Curvature in Smartphone

To develop a flexible display, smartphones with edge screens with curved displays on both sides of the main screen have been used widely. Considering that small differences in the form of smartphones, such as length, width, and thickness, could affect user experience, the effects of the curvature of the edge screen should be identified. This study aimed to investigate the effects of the curvature of edge screens on subjective feelings of smartphone users and to find out the optimal curvature. In the experiment, four nonfunctional samples with different radii of curvature (4R/6R/8R/10R) were used as samples, and participants evaluated the five subjective feelings: grip/control comfort, front/side visibility, and stability of the samples with four usage patterns. Our results revealed that 8R is the optimal curvature for the edge screen based on subjective feelings in smartphone usage. Moreover, the effect of the curvature of the edge screen on grip comfort and control comfort varied according to the usage patterns. The results of this study can be applied to design of the curvature of edge screens in smartphones and it is expected that it will contribute to improvement of users’ satisfaction.