Cheaper, Simpler Methods for Making Tiny Flexible Robots

<p>In this thesis, I present the design and fabrication of soft microactuators and microrobots. Efficient methods of producing soft polymer based microactuating devices are explored to illustrate easier and cost-effective manufacturing processes for flexible microsystems. Using innovative approaches in conventional microfabrication techniques along with unconventional additive methods, I demonstrate smart and compliant microrobotic devices to achieve multiple functionalities. Easy to scale up and implement, novel manufacturing processes are advanced to push the boundaries of control, scale, and functionality of soft microrobotic systems. </p><p>The design and control of soft microrobots is challenging due to the limitation of material properties to generate actuation motion or force. Achieving a precise motion at small scales is often difficult to introduce in microactuating devices. To illustrate directional control in microrobots, soft polymer based microactuators are presented through a simple method to integrate morphological computation in the device body. Soft microactuators were fabricated using a cost-effective method of patterning geometrical designs to induce precise control over the actuation motion. The microactuators comprised of electroactive polymer materials (conducting polymers) as the active material to drive the actuation force through electrical stimuli. Polydimethylsiloxane layers, which function as the backbone of the device providing support and control over the actuation motion, were patterned with soft lithography. Through a single manufacturing process, multiple microactuating designs can be achieved using this process. This method employs just one design template to repeatedly pattern layers, which are then selectively sliced to obtain multiple device designs; as opposed to the conventional method of photolithography, which requires multiple stages of development through different photomasks. Depending on the geometrical pattern set in the final step, microactuators with different actuation motion like spiral, screw, and tube were demonstrated with determined range of movement. </p><p>The efficient fabrication of soft robots at the micrometre scale is central to the rapidly growing field of soft microrobotics. Researchers, in this area, are investigating several fabrication techniques, such as photolithography, soft lithography, laser ablation, and additive manufacturing. Using additive techniques such as 3D printing, for example, easier design to product process can be achieved, allowing for accelerated product development. Integrating it with current manufacturing market, I believe, would enable transition of soft microrobots from experimental prototyping to efficient production, saving on energy and material costs. But the fabrication of soft robotic devices with additive manufacturing techniques is currently limited to millimetre sizes only. To push the limitations of scale, soft microactuators and devices with progressively smaller dimensions in the micrometre range are demonstrated by employing novel additive methods. Soft microactuators with minimum thickness of 20 μm were additively manufactured using a custom-built extrusion printer. A CAD model of the device structure was used to create microactuators body, which were then integrated with electroactive polymers (conducting polymers) to operate the actuators. Soft microactuators with various dimensions were fabricated to illustrate the convenience and adaptability of the printing technique. A novel method of patterning-by-printing is presented to construct microrobotic systems with selective actuation mechanism. Furthermore, to illustrate the capability of additive technique, fully printed soft microactuators and devices are presented. Driven by hydrogels, bilayer microactuators of various dimensions with a minimum thickness of 30 μm were also manufactured and operated. Microrobotic devices with a passive stiff body and active flexible moving actuators were 3D printed to demonstrate the simplicity and adaptability of the additive manufacturing process for fabricating soft microgrippers or micromanipulators. </p><p>Soft microrobots have a wide range of potential applications in areas such as biomedical engineering, environmental monitoring, and manipulation of small objects. Their ability to be processed with intricate designs and provide user defined actuation under various environments make them a perfect candidate for developing complex yet easily operable microscale devices. To demonstrate functionality, an electrically controlled dynamic microparticle filter was developed on a microfluidic chip. Micropillars combined with conducting polymers to provide radial actuation were placed in a specially designed microfluidic housing to allow sieving of microparticles of various sizes. The conducting polymer micropillars served as gates for the fluidic channel, controlling the porosity of the filter and enabling the filtration of microparticles of particular size. This sieve design allows for user-defined channel width modulation in response to an outside electrical stimulus. The functional components of the microfluidic filter were created using additive manufacturing in conjunction with the conventional techniques of lithography and electrochemical polymerisations. Selective filtration of sub-100 μm sized microparticles to illustrate the functionality of this novel configuration are displayed. To characterise the performance of dynamic microfluidic filter, the flow and aggregation of different sized microparticles was also analysed.</p>