Active bending ileus tube using shape memory alloy for treatment of intestinal obstruction

Soft and long silicone rubber tube (long intestinal tube; LIT) is commonly used for conservative treatment in intestinal obstruction (ileus). The LIT is inserted into the intestine for depressurization by continuous suction from outside the body. In insertion of the tube, it is difficult to pass the lower opening of the stomach (pylorus) because of its narrowness. An LIT that has stainless steel weights at the tip is most widely used for the insertion. This tube utilizes gravity to facilitate manipulation of the tip. However, a patient must endure pain when he or she changes position. For accurate positioning of the tip, active bending LIT using shape memory alloy (SMA) coil micro actuator, which contracts by supplying electrical current has been developed. The tube consists of a bending tip (external diameter, 6 mm; length, 40 mm) and a 3-m-long silicone rubber tube. It enables easier and more reliable passage at the pylorus. The maximum bending angle was 110 degrees and the bending tip is flexible even if it bends because of softness of the SMA micro-coil. The surface temperature of the tip during active bending motion was measured under conditions of 38°C and it takes 45 seconds for the surface temperature to rise over 41°C when the bending angle is maintained at 30 degrees.