Micrometer-scale Robotic Systems Based on Physical Integration


Student thesis: Doctoral Thesis

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Award date4 Oct 2023


Microrobots have drawn much attention from researchers due to their broad applications in many fields, such as biomedical engineering and environmental Engineering. There are two main aspects of microrobots: motion performance and functionalization of microrobots. Currently, the famous functional approach is chemical synthesis depending on the material selection and chemical decoration. But such a method restricts the functional expansion of microrobots to develop intelligent microrobots containing sensors, memory, energy elements, and other advanced capabilities. The counterpart to chemical synthesis is physical integration relying on micro-/nanofabrication technologies with great function expansion ability and excellent directional design. However, the mutual matching of motion structure and functionalization of microrobots need to be investigated, given the inadequate motion control exhibited by presently physically integrated microrobots.

Firstly, 3D micro-pinwheel structures using rolling-up technology composed of multiple flabella shapes are designed to help understand the forming mechanism of ABF. The in-situ releasing process, theoretical simulations, and structural characterization were carried out to analyze the rolling-up process and structure regulation with different designs of the 2D pattern. With the help of simulation and SEM manipulation, a tunable 3D micro-pinwheel under external force stimulus was discussed for developing the parallel microrobots and the adaptive 3D micro-antennas. Moreover, with the microscale size, the response wavelength of our 3D micro-pinwheel within the terahertz (THz) range was demonstrated for organic molecule detection.

Then, an opto-electromechanical coupling microcantilever based on the functional element was developed to investigate the integration technology on flat nanomembrane, reducing the impact on the performance of functional elements integrated into microrobots. Thanks to the micro-/nanofabrication technologies, the opto-electromechanical system was integrated into a thin film with a thickness of 180 nm. During the fabrication process, the entire chip was obtained by the combination of top-down subtractive technology and bottom-up additive technology. Finally, the Opto-electromechanical coupling effect was observed under the TEM manipulation and laser irradiation.

To achieve the fusion between the flat nanomembrane with the helical structure of ABF, the ABF with substructure (magnetic teeth as an example) integration and its impact on shaping ABF using the rolling-up technique were introduced. On such a platform, the discrete magnetic teeth embedding not only brought structural modulation in the morphology of ABF via the design of the substructure arrays along the 2D mesa pattern before rolling up into 3D helical structures but also achieved multimode motion control provided power by the magnetic teeth with an external magnetic field. Among these, the 3D forming process with different geometry structures and the kinematic performance were studied to reveal the effect of substructure on ABF.

Finally, an illustrative demonstration of physically integrated microrobots incorporating solar cells is presented, building upon the aforementioned technologies. Initially, the organic solar cell is miniaturized to a micrometer scale and patterned. Additionally, a series connection of micro-organic solar cells is established to achieve heightened output voltages. These micro-solar cells have been substantiated for their efficacy in deionized (DI) water under the laser irradiation of 808 nm. Remarkably, desirable output is also attainable when the 808 nm laser penetrates the pigskin with a thickness of 1.7 mm. Furthermore, the micrometer-scale solar cell is seamlessly integrated into the microrobots, enabling effective motion control with an external magnetic field.

In conclusion, the adoption of the rolling-up technology to form an adjustable ABF presents a viable solution for the development of micrometer-scale robotic systems through physical integration. The exceptional motion capabilities exhibited by the ABF underscore the effectiveness of this approach in ensuring reliable motion control.

    Research areas

  • microrobots, physical integration, micro-pinwheel, opto-electromechanical microcantilever, artificial bacteria flagellum, organic solar cell