Design and Experimental Evaluation of a Soft Robotic Hand for Anus Hygiene Assistance in Nursing Bed Toilets for the Elderly

Personal hygiene is vital to the well-being and dignity of the elderly, particularly as physical abilities decline. Tasks such as post-defecation cleaning in a nursing bed toilet can become difficult, often compromising autonomy and dignity. This paper presents a novel smart soft robotic hand designed specifically for elderly nursing bed toilets to assist in post-defecation anus cleaning. Fabricated from thermoplastic polyurethane (TPU), the robotic hand integrates three functional modules: an ultrasonic vibration unit, a water spray unit, and a tendon-driven transmission mechanism. The ultrasonic unit uses high-frequency vibrations to dislodge residual stool, while the water spray ensures thorough rinsing. The tendon-driven mechanism enables finger flexion and extension, allowing for effective wiping action. Its performance was evaluated experimentally in a realistic environment. Anatomically realistic models of the human anus were used along with artificial fecal material. The robotic hand achieved high positional accuracy, enabling precise and gentle cleaning with minimal pressure. The cleaning forces generated by the tendons ranged between 1 and 2.8 N, safely within comfort thresholds. Touch sensors recorded a 95% accuracy rate in contact detection. The system activation time for the water pump and ultrasonic unit averaged two seconds. Cleaning efficiency tests showed a 98% success rate in removing simulated feces, and the ultrasonic unit reduced cleaning time by 50% compared to water-only methods. The results demonstrate that the proposed soft robotic hand offers a safe, efficient, and dignified solution for elderly hygiene.