Development of an Ergonomic Method for Determination of Smartphone Hard Key Locations

Abstract

The present study proposed a design method for determination of optimal hard key locations based on analysis of preferred grip posture and preferred hard key control area, and examined the effectiveness of the method by applying it to a smartphone with 5.0” screen. 45 participants were involved for analysis of preferred grip postures and another 44 participants were recruited for measurement of preferred hard key control area. Smartphone mock-ups which allow participants to adjust the locations of hard keys in their preference were developed having similar specification of real smartphone. L (left) 3 - R (right) 1 - K (back) 1 grip posture (82.6%) that the back side of the device is supported by the index finger and L (left) 4 - R (right) 1 grip posture (11.9%) that all five fingers contribute to grasp the device hardly were the most preferred for the smartphone with 5.0” screen. The optimal hard key locations were found 77 ~ 96 mm area from the bottom for the 20 mm right hard key and 88 ~ 97 mm area from the bottom for the 10 mm left hard key. A verification with real smartphones in various use contexts is needed to apply the results to the product design since the experiments were conducted in a laboratory setting with mock-ups.