An origami-based hydraulic soft artificial detrusor

Objectives: Neurological and non-neurological disorders (e.g. spinal injuries and detrusor ageing) can impair controlled bladder emptying capabilities. Neural stimulators have been proposed to reactivate the associated neural pathways, but they feature severe long term side effects. Artificial detrusor systems might act as an alternative solution, although sparsely approached by researchers. We propose here a novel hydraulic soft bodied artificial detrusor for controlled bladder voiding. Methods: The artificial detrusor is composed of two semispherical units embracing the natural bladder. They consist of a soft silicon skin enclosing a water chamber and a flexible acetate origami skeleton (waterbomb pattern). The origami guides the shape change from domed to flat when a negative pressure is applied. This shift compresses the bladder allowing the voiding. The voiding performances (bladder volume (Vb), voiding efficiency (VE), post-voiding residual volume (PVR), and voiding time (VT)) were assessed ex-vivo on horizontally oriented porcine bladders (i.e. simulating bedridden patients). The performance was compared with both naked bladder and de-activated detrusor ones to assess the role played by spontaneous voiding and gravity, respectively. Three waterbomb detrusor filling levels were evaluated (120, 140 and 160 mL), to investigate their effect on the skeleton contraction. Results: The proposed detrusor proved an average VE of ~90% and a PVR < 20 mL, irrespective of the detrusor filling degree. When non-actuated, VE and PVR varied between 50-70% and 20-50 mL, respectively. The VT lowers from ~400 s (unactuated) to ~200 s (actuated). The Vb ranges from 75 to 100 mL, depending on the detrusor filling. Conclusions: The proposed system could efficiently restore active voiding also in bedridden patients. Design improvements are required to allow more physiological bladder volumes. Acknowledgements: The authors acknowledge INAIL (Istituto Nazionale Assicurazioni Infortuni sul Lavoro) for providing their collaboration in the framework of the BioSUP project.