Water Jet Actuation for Ultra-low Cost Endoscopy: Characterization of Miniature Nozzles Fabricated by Rapid Prototyping

Gastric cancer is the second leading cause of cancer death worldwide, accounting for over 10\% of incidence cancers. Screening programs have been shown to be effective in reducing the mortality rate through early detection; however, many factors hinder the widespread implementation of these programs in low resource settings due to their high capital cost (associated mainly with cable driven units), limited portability, and reprocessing/contamination concerns. The Hydrojet endoscopic platform was developed as a low-cost alternative for gastric cancer screening in low-income countries. The capsule, completely made of bio-compatible plastic through rapid prototyping, uses pressurized water ejected from miniature nozzles to inspect the stomach. In order to achieve full controllability of the system inside the stomach, force characterization of the water jet actuators is needed. This work aimed to: i) characterize the relationship between thrust (with changes in outer diameter) and flow rate of miniature nozzles fabricated by rapid prototyping and ii) estimate the error due to the fabrication process. Results show that the experimental reaction thrust has a comparable trend to the analytical model hence a shape coefficient can be calculated and the actual thrust estimated at each point. Experimental results show the error due to rapid prototyping to be linear, thereby allowing for algorithmic compensation.