A custom force plate for quantifying the force applied by the finger during smartphone usage

Introduction The increase in thumb activity due to smartphone use in recent years may be associated with an elevated risk of developing musculoskeletal disorders. Prior studies on hand biomechanics during touchscreen use have indicated that activities such as swiping and tapping lead to varying levels of muscle activation and ranges of motion. Currently, however, there is no device that can be used readily to measure finger forces accurately during smartphone use. Method This study presents the design of a portable force plate specifically developed to quantify fingertip forces during smartphone use. The device utilises a load-cell structure and foil strain gauges to measure applied force magnitude, direction, and location. Results The device achieved a force sensitivity of 0.15 N and a positional sensitivity of 2.5 mm, with a maximum measurable force capacity of 3 N. Discussion The portable force plate enables the study of hand kinetics whilst allowing for physiological kinematics during smartphone use, with applications spanning musculoskeletal and finite-element model development of the hand, ergonomic risk assessment, smartphone interface evaluation, and musculoskeletal injury prevention.