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Nano and Micro Technologies

Nano and Micro Technologies - Poster Session D

Poster Z7 - Empirical Validation of Microgripper Topology Optimization

Friday, October 25, 2024
3:30 PM – 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  The promise of microrobots capable of navigation and manipulation in vivo could transform disease detection and treatment. To these ends, we have developed a hybrid material approach for microrobot assembly comprised of an optical path, an environmentally responsive actuator, and a printed compliant mechanism. The compliant exoskeletal gripper head can be autonomously actuated by stimuli-responsive materials (e.g., hydrogels, elastomers) that respond to light, pH, and temperature. Toward the development of clinically relevant designs, we aimed to improve robot performance under physiological conditions, such as small changes in pH that may indicate disease. For this we employ a topology optimization approach—applied to the exoskeletal geometry—to maximize the mechanical output to environmental cues. This design-manufacture-operate optimization schema accounts for printed material properties, printer parameters, and hydrogel-environment interactions. Bringing manufacturing and operation conditions into the analytical design process facilitates robot design for specific tasks (e.g., retrieval/deployment of low to high-modulus payloads). We demonstrate that we can achieve marked improvements in design objective functions when parameters from design, fabrication, and operation are included.

Printed designs have been tested in-vitro for alignment with the analytical results. The analysis has shown that the performance of the microgripper designs in-vitro has good agreement with the analytic results. Though realizing topology-optimized forms has been well suited to additive manufacturing for static mechanics, we show that substantial increases in dynamic performance at micro/nano length scales is achievable in-vitro by integrating the complementary processes of design, manufacturing and operation.

Materials and

Methods:  Analysis of the in-vitro results was completed using image analysis of in vitro testing. To determine experimental objective function (Input/out displacement), the microgripper jaw displacement was measured by comparing the width between the jaws both right before displacement and at maximum closure for each individual test. Input distance applied to the microgripper for each test was also measured. Each measurement was made approximately 10 times and averaged to calculate values for initial jaw width, final jaw width, and input distance. These values were used to calculate an experimental objective function value using the calculation [initial jaw width – final jaw width]/[input distance]. Each experimental objective function was then compared to the respective theoretical objective function for the microgripper design, determined using a custom MatLab script.

Results, Conclusions, and Discussions: A total of 10 different microgripper designs were tested in-vitro. Speed and power sweeps of one microgripper design were also compared. Each microgripper design underwent multiple trials of testing and the average objective function for each was obtained. There is generally agreement between the experimental values determined via testing in vivo and the theoretical objective functions determined analytically. This validates that the implementation of topology optimization can create increases in performance not only theoretically but in practice on the micro-scale. We have demonstrated that increases in dynamic performance is achievable by integrating the complementary processes of design, manufacturing, and operations. The implementation of these processes in microgripper design, and the consequential agreement between theoretical and experimental results, shows this approach has the potential to improve tool design for specific applications on the micro/nano scale to advance the field of medicine.

Acknowledgements (Optional):