J Reconstr Microsurg 2006; 22 - A042
DOI: 10.1055/s-2006-947920

Detachable Microvascular Pulse Monitoring Probe with Integrated Shape Memory Alloy Thin Film Actuator

Takashi Sugawara 1, Takashi Mineta 1, Eiji Makino 1, Satoshi Toh 1, Takayuki Shibata 1
  • 1Hirosaki University School of Medicine, Department of Orthopedics; Hirosaki University Faculty of Science and Technology, Department of Intelligent Machines and System Engineering; and Toyohashi University of Technology, Department of Production Systems Engineering, Japan.

Early detection of thrombosis after microvascular anastomosis remains an unsolved problem. There are some implantable blood flow monitoring probes, for example, ultrasonic Doppler probes, but they need fixation with a cuff on the vessel surface and another surgical procedure for removal. The authors attempted to develop an implantable microvascular pulse monitoring probe with an active-motion vessel holder which can maintain stable monitoring and can be safely removed percutaneously.

The device consists of a sensor with strain gauge circuits and an actuator with micro-heaters on a shape memory alloy thin film. The holding arm can be closed and opened by activating two pairs of micro-heaters sequentially. In vitro holding and releasing forces were measured, and strain gauge properties were examined.

Photographs of the completed device were demonstrated. At the holding stage, the tensile force ranged from 20 to 40 mN at evulsion of the tube, and the force was under the measuring limit at the releasing stage. This indicated that the actuator could be removed safely without vascular damage. The strain gauge output varied approximately 100 mV for 300 μm displacement.

A prototype of a detachable microvascular pulse monitoring probe with two-step actuation was successfully fabricated. Further in vivo studies should be carried out for applications in clinical use.