Optimizing the Load Capacity of a Compliant-Mechanism-Based Microplate Gripper for Biomedical Lab Automation

Laboratory automation enhances repeatability and throughput in scientific and industrial applications. An important aspect of automation is transporting standardized components, such as microplates (MPs). Previously, we developed the compliant-mechanism-based gripper (“CrocoGrip”) to enable secure and contamination-free MP transport. However, we have yet to optimize the gripping jaws (GJs) to enable the handling of fully loaded, heavier MP. In this paper, we optimize the design and surface of CrocoGrip’s GJs to optimize its load capacity (LC). Since the CrocoGrip works like a torsion spring, the opening width, which defines the deformation of the CrocoGrip, the jaw arm length, and the jaw’s surface material are important factors affecting the LC. We tested the LC of six different jaw materials at different opening widths. The best-performing jaw surface was then also evaluated at a second jaw arm length. Jaws equipped with silicone inserts performed the best (LC = 2.93 N at the smallest opening width), while aluminum with different surface smoothness performed the worst (0.68 N ≤ LC ≤ 1.56 N). Decreasing the jaw arm length from 81 mm to 66 mm increased the LC of the silicone-insert jaws to 3.71 N at the smallest opening width. Since the friction force of silicone is surface-area-dependent, further study of the number of inserts is necessary. The improved LC allows the safe handling (safety factor of 3) of MP with a weight of up to 127 g, thus, enabling using the CrocoGrip for a broader range of tasks.