A controllable micro-lens structure for bio-analytical applications

In this study, a new and simple design of a controllable micro-lens structures capable of the enhancement of laser induced fluorescence (LIF) system has been demonstrated. Two pneumatic side-chambers were placed between a micro sample flow channel and an optic fiber channel. The interval between the side-chamber and the micro sample channel was used to form a controllable micro-lens structure. A deformation of the micro-lens structure can be generated after a pressurized index-matching fluid was injected into the pneumatic side-chambers. The side-chambers can be deflected as a convex lens to focus both the laser light source and the fluorescence emission. The profile and the focal length of the micro-lens structure can be adjusted by using different applied pressures accordingly so that bio-samples with a low concentration can be detected. Using low-cost polymeric materials such as polydimethylsiloxane (PDMS), rapid and reliable fabrication techniques involving standard lithography and replication process was employed for the formation of the proposed chip device. Finally, experimental results clearly revealed the micro-lens structure can be deformed as a convex lens to focus the laser light source and the fluorescence signal can be enhanced successfully. The developed device has a great potential to be integrated with other microfluidic devices for further biomedical applications.