Scalable CMOS Manufacturing of Micro-Opto-Electro-Mechanical and Micro-Robotic Systems

Abstract

This thesis presents a framework for the scalable fabrication, wavelength-selective control, and multimodal deployment of sub-millimetre micro-robotic systems, realised entirely through CMOScompatible processes. Employing a bottom-up engineering methodology, the work unifies MEMS manufacturing, opto-thermal actuation, and plasmonically enhanced spectral selectivity, culminating in a suite of micro-robots capable of operating across terrestrial, aquatic, and aerial environments. These systems are actuated untethered via spatially and spectrally modulated optical inputs—without the need for on-board electronics, wiring, or embedded logic. In addition to mobile robots, this platform enables high-precision micro-gripping structures, leveraging the same opto-thermal principles to achieve controlled multi dimensional out-of-plane actuation. These grippers demonstrate the capability for object manipulation at the micro-scale, offering a pathway towards high precision cell handling, micro-assembly, and interactive robotic tasks in constrained environments. Micro-robotic devices were fabricated using a process stack incorporating photolithography, electron beam lithography, reactive ion etching, and physical vapour deposition. Suspended bimorph actuators were integrated with nanostructured gold plasmonic disk arrays engineered for localised surface plasmon resonance. Finite element analysis simulations, supported by ellipsometry and darkfield spectroscopy, were employed to correlate optical absorption to wavelength-dependent actuation efficiency. Three classes of optically controlled micro-robots are demonstrated: (1) terrestrial robots that employ cyclic thermo-mechanical deformation to walk and pivot across silicon substrates; (2) aquatic swimmers, using asymmetrically heated paddle arms to generate propulsion in viscous fluids; and (3) aerial prototypes featuring optically driven flapping mechanisms for oscillatory thrust. Locomotion was quantified via kinematic tracking, revealing deterministic, curvature-tunable paths under wavelengthand frequency-specific illumination. A key innovation lies in the plasmonic architecture: disk arrays tuned to specific resonances exhibit actuation enhancements of up to 2×, with spectral selectivity. This enables concurrent, wavelengthmultiplexed control of distinct robots within a shared optical field—a paradigm shift from electrodebased actuation and addressing the need for untethered control. The result is a platform that supports massively parallel actuation using nothing more than light and engineered material responses. By combining scalable MEMS fabrication with structurally meta-surface-encoded optical functionality, this thesis advances the state-of-the-art in untethered micro-robotics and lays the groundwork for intelligent, microsystems governed not by electronics, but by the physics of light–matter interaction.

Date of Award	23 Sept 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Matthew Halsall (Co Supervisor) & Tim Echtermeyer (Main Supervisor)