Conceptual Design of a Bedsore Prevention Sitting Cushion - based on Jamming transition

Min-yung Kim, et al. (2021)

Overview

 A bedsore is an injury caused by pressure on the skin and the tissue underneath it. According to the national survey on wheelchair accidents in Korea, 45.8% of the accidents relating to physical  injuries were bedsore. The best way to prevent bedsore is to change positions regularly, however, it is a difficult task for waist-down paralysis patients who cannot voluntarily move their body. The patients need constant concentration and physical assistance of caretakers to effectively prevent a bedsore. Thus, we made a conceptual design of a bedsore prevention sitting cushion for waist-down paralysis patients to change their positions on their own. We deployed a jamming transition system with a porous material to make the cushion fit to users' bodies and developed lifting mechanism to move the center of mass of the cushion. 

Jamming Transition

Jamming transition is a phenomenon in which when small particles are gathered, it becomes hard in a vacuum state and becomes soft when air is injected. A gripper based on this principle is called jamming gripper. There is a small particles in the pouch which is the end effector and by controlling the airflow, it creates a grip that fits the object's shape and holds the object. (see Figure 1)

 We used this principle to make the cushion fit to the users body by the following process. (see Figure 2)

 However, due to the solid vacuum state of the cushion, the cushion loses its important human factor, comfortableness. Based on the user interview, we defined comfortableness as the important factor when using any kind of sitting cushions. The softness is also important to prevent the bedsore. Thus, we used the principle of the jamming gripper supported by a porous material (see Figure 3)