An adhesive bonding technology for endoscope lenses that can better withstand sterilisation has been developed by scientists at the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research in Bremen, Germany.
Medical endoscopes need repeated sterilisation but the extreme temperature fluctuations during cleaning can cause the lenses to expand and contract. Because they are made from different types of glass, the lenses become uneven, leading to deformation of the bonding layers. After testing different acrylates and appoxites, researchers found that when adhesives are hardened with light, in the range of 100mW/cm2, and heat-treated, they become better at withstanding temperature shocks. ‘The UV light [and curing] depends on the adhesive,’ says Dr Thomas Gesang, a microbonding specialist at Fraunhofer. ‘We have developed a micro-adhesive bonding technology which has such a low internal stress level inside the joint that it can withstand external stresses better than former designs.’ He says the new endoscope can still perform well after 1,000 sterilisation cycles. The process is only applicable for endoscopes where the adhesive bond is buried deep within the instrument, but he says it could be adapted for other endoscopes.