was derived by calculating the angle between the axis in the height direction and the line connecting the floor and the end-tip trajectory. For the gripping force measurement, a regulated constant pressure (from 100 kPa to 220 kPa with 20 kPa increment for each experiments) was applied to the two-finger gripping unit holding a cylinder located at the end of the rail connected to a load cell (333FDX, KTOYO) and a linear actuator (P16-P, Actuonix Motion Devices, Inc.). To estimate the scale of friction, the rail without external gripping force was also pulled and the friction force was measured to be as low as below 50 gf.
Gripping tasks: Movie S5 shows the soft gripper successfully conducting gripping tasks designated at the manipulation competition of Robosoft 2021. The first task requires strength to grip a heavy and large fruit (1-2 kg), and the second task requires delicacy to grip a small sized delicate fruit. Korean radish weighing 1.3 kg and raspberry were chosen respectively. The third and fourth tasks were to pick a coin an insert it into a coin slot, requiring precision and dexterity respectively. The Korean 100-won coin (24 mm diameter) was chosen and the coin slot was fabricated as 4 mm