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Miniaturizing legged robot platforms is challenging due to hardware limitations that constrain the number, power density, and precision of actuators at that size. By leveraging design principles of quasi-passive walking robots at any scale, stable locomotion and steering can be achieved with simple mechanisms and open-loop control. Here, we present the design and control of “Zippy”, the smallest self-contained bipedal walking robot at only 3.6 cm tall. Zippy has rounded feet, a single motor without feedback control, and is capable of turning, skipping, and ascending steps. At its fastest pace, the robot achieves a forward walking speed of 25 cm/s, which is10 leg lengths per second, the fastest biped robot of any size by that metric. This work explores the design and performance of the robot and compares it to similar dynamic walking robots at larger scales. 

Miniaturizing legged robot platforms is challenging due to hardware limitations that constrain the number, power density, and precision of actuators at that size. By leveraging design principles of quasi-passive walking robots at any scale, stable locomotion and steering can be achieved with simple mechanisms and open-loop control. Here, we present the design and control of "Zippy", the smallest self-contained bipedal walking robot at only 3.6 cm tall. Zippy has rounded feet, a single motor without feedback control, and is capable of turning, skipping, and ascending steps. At its fastest pace, the robot achieves a forward walking speed of 25 cm/s, which is10 leg lengths per second, the fastest biped robot of any size by that metric. This work explores the design and performance of the robot and compares it to similar dynamic walking robots at larger scales. 

This paper presents polycarbonate negative topographies used as substrates for the templated self- assembly of microsphere-based microrobots. This approach protects primary structures from damage during molding and de-molding, providing high fidelity negatives of arrays for assembly via templated assembly by selective removal (TASR). We show that reducing the surface energy mismatch between the microspheres and substrate results in yield increases up to 790%. This work addresses yield-related challenges of multicomponent microsystem assembly with existing PDMS-based templated assembly methods. The application of this technology in DNA microswimmer fabrication is demonstrated. 

Our ability to measure and image biology at small scales has been transformative for developing a new generation of insect-scale robots. Because of their presence in almost all environments known to humans, insects have inspired many small-scale flying, swimming, crawling, and jumping robots. This inspiration has affected all aspects of the robots’ design, ranging from gait specification, materials properties, and mechanism design to sensing, actuation, control, and collective behavior schemes. This article highlights how insects have inspired a new class of small and ultrafast robots and mechanisms. These new robots can circumvent motors’ force-velocity tradeoffs and achieve high-acceleration jumping, launching, and striking through latch-mediated spring-actuated (LaMSA) movement strategies. In the article, we apply a solution-driven bioinspired design framework to highlight the process for developing LaMSA-inspired robots and systems, starting with understanding the key biological themes, abstracting them to solution-neutral principles, and implementing such principles into engineered systems. Throughout the article, we emphasize the roles of modeling, fabrication, materials, and integration in developing bioinspired LaMSA systems and identify critical future enablers such as integrative design approaches. 

Magnetically-actuated swimming microrobots are an emerging tool for navigating and manipulating materials in confined spaces. Recent work has demonstrated that it is possible to build such systems at the micro and nanoscales using polymer microspheres, magnetic particles and DNA nanotechnology. However, while these materials enable an unprecedented ability to build at small scales, such systems often demonstrate significant polydispersity resulting from both the material variations and the assembly process itself. This variability makes it difficult to predict, let alone optimize, the direction or magnitude of microswimmer velocity from design parameters such as link shape or aspect ratio. To isolate questions of a swimmer's design from variations in its physical dimensions, we present a novel experimental platform using two-photon polymerization to build a two-link, buoyant milliswimmer with a fully customizable shape and integrated flexible linker (the swimmer is underactuated, enabling asymmetric cyclic motion and net translation). Our approach enables us to control both swimming direction and repeatability of swimmer performance. These studies provide ground truth data revealing that neither the first order nor second order models currently capture the key features of milliswimmer performance. We therefore use our experimental platform to develop design guidelines for tuning the swimming speeds, and we identify the following three approaches for increasing speed: (1) tuning the actuation frequency for a fixed aspect ratio, (2) adjusting the aspect ratio given a desired range of operating frequencies, and (3) using the weaker value of linker stiffness from among the values that we tested, while still maintaining a robust connection between the links. We also find experimentally that spherical two-link swimmers with dissimilar link diameters achieve net velocities comparable to swimmers with cylindrical links, but that two-link spherical swimmers of equal diameter do not. 

Abstract Active colloids are modular assemblies of distinct micro‐ and nanoscale components that can perform complex robotic tasks. While recent advances in templated assembly methods enable high‐throughput fabrication of multi‐material active colloids, their limitations reduce the ability to construct flexibly linked colloidal systems, restricting their complexity, agility, and functionality. Here, templated assembly by selective removal (TASR) is leveraged to construct multicomponent colloidal microstructures that are connected with compliant DNA nanotube linkages. Polycarbonate heat (PCH) molding is employed to create high‐surface‐energy templates for improved polystyrene microsphere assembly via TASR. This increase in template surface energy improves microsphere assembly by more than 100‐fold for two‐sphere microstructures. An inverse relationship between microstructure complexity (i.e., the number of microspheres) and assembly yields is observed. PCH‐assisted TASR is leveraged to construct larger colloidal structures containing up to 26 microspheres, multi‐sphere microrotors, and structurally homogeneous populations of flexibly linked, two‐sphere microswimmers that locomote in fluid environments. Real‐time modification of a microswimmer is also demonstrated through nuclease‐mediated degradation of the DNA linkages, highlighting the DNA‐enabled reconfiguration and responsiveness capabilities of these microswimmers. These results establish PCH‐assisted TASR as a versatile method for constructing flexibly linked, modular microrobots with controlled geometry, enhanced agility, and dynamic response.