Flexographic and Inkjet Printing of Polymer Optical Waveguides for Fully Integrated Sensor Systems

Abstract

Planar optronic sensor systems are networks of integrated light sources, detectors and sensors, connected by optical waveguides on thin polymer films. This way, sensor networks can be realized completely optically for measuring quantities such as temperature, strain or chemical concentration. Applications unfold in structural health monitoring and chemical analysis. Waveguides represent a key element in this concept for signal transmission and the integration of interacting system components. The cost-effective and high-throughput production of polymer waveguides can be achieved by utilization of flexographic and inkjet printing. This particular application of the flexographic printing process is investigated for the first time and results show the suitability of the unique approach for production of waveguides with a minimum lateral dimension of 50 microns and parabolic cross sections. Inkjet printing is used as a complementary technique to deposit small amounts of materials at specific locations on substrates prestructured by flexographic printing. Additionally, inkjet printing allows for a thinner diameter of polymer waveguides if required, and new designs can be created easily as this process does not require invariable masks or printing forms. We show the structure of printed waveguides in layer systems consisting of core and claddings and discuss the challenges of additive manufacturing in a printing process. The resulting geometrical properties of the novel production process are described as the basis for a subsequent integration of sensors, sources, and sinks.