Development of haptic devices using flexible sheets for virtual training of abdominal palpation

A haptic device using flexible sheets for virtual training of abdominal palpation is proposed, mainly focusing on light and deep palpation. This device forms a semicylinder using two boards with rounded corners and two layered flexible sheets made of rubber. The device imitates the form of an abdomen. A trainee doctor touches and pushes everywhere of the upper sheet directly with his/her fingers and palm or single hand and both hands, regarding it as a virtual abdomen. Pulling the lower sheet lengthwise varies the softness of the sheet: the stretched sheet feels hard and the loose sheet feels soft. The trainee doctor can feel different softness of abdomens by pushing the device. Pulling the upper sheet in waistline direction depresses the centre of the device between the boards like a saddle. Stretching and loosening the upper sheet simulates up-and-down movement of an abdomen due to breathing. As a result, the trainee doctor can experience virtual abdominal palpation in the similar way as real palpation. The softness and depression at the centre of the device are measured for different tensions of the upper and lower sheets, and are compared with the measured softness and up-and-down movement due to breathing of real abdomens. A skilled physician evaluates that the device can present different softness in the range of softness of real abdomens and that the up-and-down movement of the device resembles that of real abdomens due to breathing. The empirical and sensory criterion of the physician is ascertained quantitatively using the device: he pushes abdomens until he feels the same reaction force, regardless of their softness.