Design, Manufacture and Testing of Polymer Grippers for Micro Handling

The development of solutions for different handling and assembly processes, used for manipulation of real three dimensional micro objects has been investigated in this thesis work. The individual micro parts were studied with respect to materials, weight, geometry and dimensions. Handling and assembly at a micro scale are challenging because these processes are dominated by surface forces and not the gravity force, which gives problems such as stiction to the gripping tool. As a consequence, high precision centering and alignment, as well as high accuracy micro assembly with low tolerance are difficult to achieve. A literature survey about handling of micro objects was carried out and it was found that it is possible to use structured surface to grasp and release micro objects. At DTU a mould with a pyramidal microstructure was available and replicas with two different polymeric materials were produced. A smooth membrane with the same materials used with the pyramid structured one was also manufactured for comparison. It was designed a system to move the membrane and grasp and release micro objects; the system is composed by a piston with spherical end, it slides in a cylinder where at the end the membrane is glued. The system is moved and regulated by a micrometer. The piston bends the membrane so that the desired curvature to achieve grasping and releasing of micro objects is obtained. To understand if the different membranes were influenced by humidity, a drop of water was applied to the surface and, through a digital micro camera, it has been possible to measure the quantity of water in touch with membrane. The membranes were tested. A particular material with both the smooth surface and the grey pyramidal was investigated; the results show that the pyramid structured membrane is more hydrophilic than the grey smooth membrane. Lastly the grasp and release tests with the grey smooth membrane and with the grey pyramidal one, showed that the micro object is grasped equally with two membranes, while it is released with less deformation with the smooth membrane that with the pyramidal one