At the Forschungszentrum Karlsruhe a microturbine and a valve system are being developed to be integrated on cardiac catheters. Prototypes have been designed to open occluded coronary arteries and to test the in-vitro cutting of calcified arterial plaque. The research is being embedded in the Esprit project IMICS. The institute plans further research in close cooperation with hospitals for specific applications in order to optimise the integrated catheter system for commercial production.
The microturbine consists of a rotor with radial blades which is mounted on a shaft. The rotor is surrounded by a nozzle plate. These microcomponents are assembled into a housing regulating the fluid flow. The fluid is injected into the rotor through the nozzle plate where it is drained back again. The turbine is driven by a balanced salt solution which makes a certain leakage uncritical. The fairly high torque and rotational speed of the turbine result in a considerable power. The operation pressure is defined by the nozzle geometry. Due to its small dimensions, the turbine is fabricated by microtechniques such as injection moulding. The microcomponents are batch produced which means that many pieces are mounted in parallel. Low prices are the result of this process.
The valve system has been designed for the steering of a laser beam inside blood vessels. The size of the small balloons on the catheter's tip can be varied in order to make it move relatively to the vessel walls. A microvalve system permanently controls the size of the inflatable balloons by means of pressure regulation inside them. Six molded multi-level platelets are mounted onto a steel tube together with a polyimide membrane and resistive heaters. The fluid passes the valves through the flexible hose and fills the balloons. Inflation is caused due to flow resistances. The electrical heating of an actuator chamber activates the valves and forces the membrane against a valve seat. A laser beam can be carried via an optical fibre which is passed through the catheter together with the electrical connections.
Through the application of both microturbine and valve system, the integrated catheter system is capable of providing within a single device all the functions associated with in vivo sensing, diagnosis and removal of arterial plaque. More information on the microsystems technology program in medical engineering is to be found at the Forschungszentrum Karlsruhe web site.