Sometimes it begins with a slight pulling sensation in the back, while at other times it can put a person completely out of action from one minute to the next: These are the symptoms of a slipped disk. An operation is not always necessary, as there are effective alternatives to surgery.
One method is to puncture the spinal disks. This involves injecting medicine into the injured area of the body with a thin needle. To be able to monitor the operation at all times and position the instruments accurately, the surgeon requires an image of the affected area. This can be obtained using magnetic resonance imaging (MRI). "The problem so far, however, was that conventional metal instruments interfere with the magnetic field of the MRI and distort the picture," explains Sebastian Schmitz of the Fraunhofer Institute for Production Technology IPT. "Our task was to develop instruments made out of fiber reinforced composite materials for use in the tomograph, as these materials afford a clear view."
But how to produce a carbon-fiber-reinforced plastic puncture needle that is just as firm and rigid as those made from stainless steel? The engineers have now developed a new manufacturing process. Up to eight thousand individual carbon fibers are treated in a miniaturized pultrusion process: The fibers are soaked in a thermosetting plastic, which is then heated until it sets. At the same time, high pressure is applied to press the fibers together and into the desired shape. Both processes must take place simultaneously without hindering each other. To incorporate a working channel into the needles, the engineers use hollow glass fibers that are processed together with the carbon fibers. The patented needles have now entered series production on the basis of this method.