Medical products and components in the bio-engineering and bio-analysis
sector have to be made from highly bio-compatible materials that are
inert vis-à-vis a variety of media. The joining method employed
also has to meet special requirements. It has to get by with as few
additive materials as possible, and should under no circumstances
influence or contaminate the materials. As an alternative to
conventional joining techniques, laser welding offers a number of
innovative solutions featuring high welding speeds, narrow weld seams
and special process variants for joining transparent plastics.
A series of new beam sources enables laser characteristics to be
specially adapted to these tasks. Highly advanced microsystems with
complex welding contours for medical engineering and biotechnological
applications, such as a new type of microfluidic chip with very narrow
and closely spaced channels, make great demands on joining technology.
The new chip has to be furnished with a cover film, for which the
welding seam must be no more than 100?m wide.
The new TWIST® (Transmission Welding by Incremental Scanning
Technique) contour-welding method developed by the Fraunhofer Institute
for Laser Technology ILT meets these stringent requirements, producing
high-quality welding seams at high process speeds. Based on fiber
lasers, this innovative irradiation method can produce
100-?m-wide seams at a rate of up to 18 m/min. Any potential
degradation of the material due to the high intensity of the focused
fiber laser light is avoided in the new process. For the welding of
transparent plastics, the new beam sources enable the laser
characteristics to be adapted to the polymers’ absorption
behavior, thus obviating the need for additional absorbers. This
improved irradiation strategy preserves the advantages of laser
transmission beam welding without influencing the surfaces of the
components. It can be used for transparent and translucent polymers.
Figure 1: Films welded using the TWIST® techniqueFigure 2: Welding of two transparent components without an absorber
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