Design of a Device for Manipulating Small Objects in a Solution Design Team: James Black, Seong Byun, Jeremy Johnson, Nathan Wagers ME 462 Capstone Design Advisor: Dr. Hazim El-Mounayri Sponsor: Dr. Jie Chen Problem Definition : In medical research, there is a need to extract very small objects from solution in order to transport and deliver them precisely to another location. Specifically, single cells must be collected and transported safely and securely, and this function is difficult with commercially available pipettes. Design Requirements: (1) Extract single cell (< 0.1mm in size) from solution, (2) Hold it securely during transport, (3) Dispense (4) Accommodate preexisting glass tip, (5) Be easily operated by one hand, (6) Be easily reset to preoperational condition, (7) Cost less than $150. Design Development: The control of a minute volume directed the use of precise lateral motion within the space constraints of one hand. This controlled lateral motion could be satisfied in the most cost-effective manner with a finely threaded shaft. To ensure proper sealing while maintaining adequate vacuum pressure, a rubber membrane was chosen over a costly wire plunger syringe concept. Validation: Prototypes of all components were physically assembled as in Fig. 2 below. Conclusions: Future finite element non-linear analysis (FEA) should be completed on the membrane stresses and displacements in relationship to the applied forces from the ball bearing/screw tip. With further investigation of computational fluid dynamics (CFD), even more control over a single cell at the tip could be achieved. Analysis of vacuum pressure within the device as a function of membrane deflection would offer ideas of optimization. Final Design: The final product consists of six components, excluding the preexisting glass tip assembly. These components include rotary knob, finely threaded screw, ball bearing, butyl rubber membrane, and the two- piece main cylinder assembly for containment of the membrane-ball- screw interface. The finely threaded screw, 0-80 UNF, controls precise axial motion of the ball atop the elastic membrane as seen in Fig. 1 of the Pro/Engineer assembly. Fig. 1: Full Pro/E Assembly and Detailed Membrane Interface The resulting design is both affordable and ergonomically pleasing for use in one hand, where rotary knob is manipulated between fingertips. Acknowledgments: We would like to thank Dr. Jie Chen, Dr. Hazim El-Mounayri, Rudy Earlson, and Dr. Sherry Clendenon for their aid in making our design project a success. The yellow rotary knob at the top of the prototype at left was created using rapid prototyping capabilities. Validation of a gas-tight seal was accomplished as in Fig. 3 below using a hand vacuum pump. Fig. 2: Full Prototype of Device Field testing was completed for validation of single cell collection using a micromanipulator base, high- res optical microscope, and imaging video equipment as seen below in Figs Control of a single object at the tip was successfully reached with hand-held knob rotation of 5-10 degrees for extraction of the cell. Fig. 3: Vacuum Testing of Prototype Fig. 4: Before Extraction of CellFig. 5: After Extraction of Cell The physical experiment revealed that the final design meets design requirements when coupled with a pre- existing micromanipulator base. An earlier concept of a finely adjusted base Fig. 6: Micromanipulator Base as seen in Fig. 6 should be pursued for specific use with the final concept to attain accurate 2D linear glass tip motion.