Light-Tuned Actuators for the Passive Flight Modes

Abstract

The emergence of intelligent, stimuli-responsive materials has transformed small-scale robotics, enabling systems that can walk, swim, and roll with increasing autonomy without relying on conventional cables or electronics. Extending these capabilities into the aerial domain presents a greater challenge, demanding new approaches to materials, structural design, and aerodynamics. Powered flight—whether via flapping wings or propellers—remains the benchmark for aerial mobility, but it requires a lift-to-weight ratio above unity, alongside high energy density and thrust generation. Despite progress in actuation technologies, no wirelessly powered centimetre-scale robot based on stimuli-responsive actuators has yet achieved continuous flight.

An alternative strategy takes inspiration from passive dispersal in nature. Seeds such as dandelion diaspores, maple samaras, and Javan cucumber seeds employ highly optimized structures to exploit wind currents and pressure differentials, sustaining long airborne times with minimal energy cost. Engineering synthetic analogues of these strategies offers a promising path for robotic flight, especially where energy conservation is essential. Unlike natural dispersers, however, stimuli-responsive materials enable active tuning of geometry during flight, offering a degree of control and adaptation never realized in biology. Yet, such responsiveness introduces potential instability, highlighting the challenge of balancing aerodynamic stability with maneuverability.

This thesis explores bio-inspired aerial locomotion through light-responsive materials, demonstrating a new class of robotic flyers capable of light-tuned gliding and mid-air shape adaptation. By coupling photomechanical actuation with aerodynamic design, we present several passive flyers that achieve controlled ascent and descent, directional steering in three dimensions, and prolonged airborne stability. Systematic refinement of materials, geometry, and aerodynamics yields flight behaviors that rival, and in some cases surpass, those of natural passive systems. These findings highlight how responsive materials can redefine aerial robotics, advancing lightweight, efficient, and controllable platforms for sustainable airborne exploration.