Untethered Microrobots of the Rolling, Jumping & Flying kinds

In this dissertation we study microrobot design for three modes of locomotion, namely rolling, jumping, and flying. This work covers power electronics, actuator and mechanical transmission design for these types of microrobots along with power source selection. Though interesting, we do not cover the sensors, controllers/computers, communications and useful payloads for these bots. This remains a topic for future work. Piezoelectric and electrostatic actuators generally have been the actuators of choice for researchers working in microrobotics, since conventional electromagnetic motor designs don't scale down well. Here we design an electromagnetic actuator in a way that significantly reduces its scaling down disadvantages, while still retaining its original advantages. This has enabled us to achieve untethered operation for our bots, which is one of the coveted goals for researchers working in this domain. Though untethered rolling and jumping is demonstrated, the untethered flying bot reported in this dissertation remains underpowered and doesn't take flight yet. First a micro-ratcheting mechanism is developed as a means to convert small periodic motions of actuators to continuous rotational motion. A supercapacitor, a fixed frequency H-bridge, and a low-voltage electromagnetic actuator is then used to drive this micro-ratchet to achieve untethered rolling motion for 8 seconds at 27mm/s. At 130mg mass, this is the lightest and fastest untethered rolling microrobot reported yet. The same continuous rotation mechanism developed for the rolling bot is then used to load a spring in an energy storage mechanism that can then release the stored energy rapidly and passively, via use of magnets, after the stored energy crosses a certain threshold. In this case, the continuous rotation mechanism is driven using laser-powered photovoltaic cells and untethered jumping up to heights of 8mm is demonstrated. At 75mg mass, it is the lightest untethered jumping microrobot with onboard power source. Next, a highly efficient resonant low-voltage electromagnetic actuator is developed to generate insect-like flapping wing motion. It is demonstrated to produce 90% of its weight in lift. Further light-weight and power-efficient power electronics are developed to power this actuator using laser-powered photovoltaic cells. The designed power electronics are an order of magnitude lighter and two orders of magnitude more efficient than all other power electronics units reported yet for flying microrobots. While sufficient lift for flight is not achieved, due to the actuator being underpowered because of power source overheating, untethered flapping wing motion is demonstrated. To provide inspiration to future generations of microroboticists, a fruit fly scale flapping winged robot is developed. At 0.7mg mass, even though tethered, it is the lightest and smallest bot to demonstrate flapping wing kinematics

Design, Actuation, and Functionalization of Untethered Soft Magnetic Robots with Life-Like Motions: A Review

Soft robots have demonstrated superior flexibility and functionality than conventional rigid robots. These versatile devices can respond to a wide range of external stimuli (including light, magnetic field, heat, electric field, etc.), and can perform sophisticated tasks. Notably, soft magnetic robots exhibit unparalleled advantages among numerous soft robots (such as untethered control, rapid response, and high safety), and have made remarkable progress in small-scale manipulation tasks and biomedical applications. Despite the promising potential, soft magnetic robots are still in their infancy and require significant advancements in terms of fabrication, design principles, and functional development to be viable for real-world applications. Recent progress shows that bionics can serve as an effective tool for developing soft robots. In light of this, the review is presented with two main goals: (i) exploring how innovative bioinspired strategies can revolutionize the design and actuation of soft magnetic robots to realize various life-like motions; (ii) examining how these bionic systems could benefit practical applications in small-scale solid/liquid manipulation and therapeutic/diagnostic-related biomedical fields

Rapid Polymer Prototyping for Low Cost and Robust Microrobots

The Rapid Microrobot Prototyping (RaMP) Process uses Loctite(R) photo-patternable polymer products and photolithography to rapidly fabricate robust, inexpensive, and compliant robots. The process is developed and examined on two size scales. On the size scale of several centimeters, two functional robots and a small gripper have been designed and demonstrated with shape memory alloy (SMA) used for actuation. The gripper is 1.2g and costs $3.21 while the inchworm robot is 7.4g and costs$7.76 in small numbers. The second robot costs $14.93 in small numbers. On the sub-centimeter scale, designs and considerations for a walking microrobot fabricated with the process and its control are fully described. The design and kinematics of a thermally actuated, one degree of freedom leg for the microrobot are developed and simulated. Several of these units could be combined to rapidly build a 30 mg functional and simple walking microrobot with the ability to lift several grams

Towards enduring autonomous robots via embodied energy.

Autonomous robots comprise actuation, energy, sensory and control systems built from materials and structures that are not necessarily designed and integrated for multifunctionality. Yet, animals and other organisms that robots strive to emulate contain highly sophisticated and interconnected systems at all organizational levels, which allow multiple functions to be performed simultaneously. Herein, we examine how system integration and multifunctionality in nature inspires a new paradigm for autonomous robots that we call Embodied Energy. Whereas most untethered robots use batteries to store energy and power their operation, recent advancements in energy-storage techniques enable chemical or electrical energy sources to be embodied directly within the structures and materials used to create robots, rather than requiring separate battery packs. This perspective highlights emerging examples of Embodied Energy in the context of developing autonomous robots

Novel Integrated System Architecture for an Autonomous Jumping Micro-Robot

As the capability and complexity of robotic platforms continue to evolve from the macro to micro-scale, innovation of such systems is driven by the notion that a robot must be able to sense, think, and act [1]. The traditional architecture of a robotic platform consists of a structural layer upon which, actuators, controls, power, and communication modules are integrated for optimal system performance. The structural layer, for many micro-scale platforms, has commonly been implemented using a silicon die, thus leading to robotic platforms referred to as "walking chips" [2]. In this thesis, the first-ever jumping microrobotic platform is demonstrated using a hybrid integration approach to assemble on-board sensing and power directly onto a polymer chassis. The microrobot detects a change in light intensity and ignites 0.21mg of integrated nanoporous energetic silicon, resulting in 246µJ of kinetic energy and a vertical jump height of 8cm

Multimodal locomotion ultra-thin soft robots for exploration of narrow spaces

From power plants on land to bridges over the sea, safety-critical built environments require periodic inspections for detecting issues to avoid functional discontinuities of these installations. However, navigation paths in these environments are usually challenging as they often contain difficult-to-access spaces (near-millimetre and submillimetre-high gaps) and multiple domains (solid, liquid and even aerial). In this paper, we address these challenges by developing a class of Thin Soft Robots (TS-Robot: thickness, 1.7mm) that can access narrow spaces and perform cross-domain multimodal locomotion. We adopted a dual-actuation sandwich structure with a tuneable Poisson's ratio tensioning mechanism for developing the TS-Robots driven by dielectric elastomers, providing them with two types of gaits (linear and undulating), remarkable output force (~41 times their weight) and speed (1.16 times Body Length/s and 13.06 times Body Thickness/s). Here, we demonstrated that TS-Robots can crawl, climb, swim and collaborate for transitioning between domains in environments with narrow entries