Microclear – A novel method for diode laser welding of transparent micro structured polymer chips

Laser welding is a well established method for bonding of polymers. However, reliable and fast bonding of transparent micro structured polymer chips used as bio chemical sensor disposables with transparent cover foils show a lot of unsolved problems. On the one hand these originate from the filler particles necessary for the welding process, which could cause fluorescence which is mostly undesirable for the bio-medical applications with optical detection. On the other hand, a large effort has to be made with conventional welding methods such as quasi-contour welding and mask welding techniques since a precise alignment between mask and work piece or laser spot and microstructure, respectively, is required. Furthermore, they require expensive polymers with dye fillers. These problems could be overcome with the newly developed Microclear technology. Thereby a mask-less welding technique using a laser-diode bar with a line focus in combination with a special absorber layer technique is applied. In the cover foils a dye absorber interface layer is generated by controlled in-diffusion of a laser radiation absorbing dye, into which the laser energy is deposited. No additional carrier material is required for the generation of the absorber layer. Due to the very local confinement of the laser energy in the thin interface region, thermal damage of the micro-structured substrate is avoided and the radiation itself does not have to be confined to the contact zone of both weld partners. Experimentally the novel Microclear technology is successfully demonstrated by welding of multi-channel polymer chips used for electrophoresis.Laser welding is a well established method for bonding of polymers. However, reliable and fast bonding of transparent micro structured polymer chips used as bio chemical sensor disposables with transparent cover foils show a lot of unsolved problems. On the one hand these originate from the filler particles necessary for the welding process, which could cause fluorescence which is mostly undesirable for the bio-medical applications with optical detection. On the other hand, a large effort has to be made with conventional welding methods such as quasi-contour welding and mask welding techniques since a precise alignment between mask and work piece or laser spot and microstructure, respectively, is required. Furthermore, they require expensive polymers with dye fillers. These problems could be overcome with the newly developed Microclear technology. Thereby a mask-less welding technique using a laser-diode bar with a line focus in combination with a special absorber layer technique is applied. In the cover ...