Laser bonding of conductive tracks on textiles with adapted wavelengths for smart textile applications

Smart textiles incorporate materials capable of adapting to environmental changes or electronic components. Electronic components require conductive tracks to be supplied with electricity and to send, for example, information about the environment regarding temperature or humidity. Normally, the production of conductive tracks involves preprocesses and postprocesses like cleaning, coating, and surface modification to improve adhesion or punching, which can result in a damage of the textile. Common methods for the application include printing, embroidery, or weaving. Printing and coating require postprocesses to secure the conductive elements on the fabric. A new approach is the bonding of metal foils by means of laser radiation. To achieve good absorption within the material and eliminate the need for additional steps, adapted wavelengths are used. Challenges for the laser bonded conductive tracks include the durability, flexibility, cost, and compatibility. Initial tests have shown that it is possible to bond conductive tracks with a laser beam that can withstand a specific amount of abrasion and washing cycles. Copper is one of the most important materials regarding electrical signal transmission and shows good absorbance of the wavelength range around 450 nm (blue light) and most thermoplastic polymers around 2 μm. Trials are carried out with different textiles (pure polymers and mixed fabrics) and the parameters such as laser power and welding speed are varied. The conductive tracks are tested regarding abrasion resistance, and the conductivity is measured after specific cycles. Tensile tests are used to check the damage to the textile because of the heat input.