Arthrobots

This paper describes a class of robots—“arthrobots”— inspired, in part, by the musculoskeletal system of arthropods (spiders and insects, inter alia). An exoskeleton, constructed from thin organic polymeric tubes, provides lightweight structural support. Pneumatic joints modeled after the hydrostatic joints of spiders provide actuation and inherent mechanical compliance to external forces. An inflatable elastomeric tube (a “balloon”) enables active extension of a limb; an opposing elastic tendon enables passive retraction. A variety of robots constructed from these structural elements demonstrate i) crawling with one or two limbs, ii) walking with four or six limbs (including an insect-like triangular gait), iii) walking with eight limbs, or iv) floating and rowing on the surface of water. Arthrobots are simple to fabricate, inexpensive, light-weight, and able to operate safely in contact with humans.Chemistry and Chemical Biolog

Experimental Studies and Dynamics Modeling Analysis of the Swimming and Diving of Whirligig Beetles (Coleoptera: Gyrinidae)

Whirligig beetles (Coleoptera, Gyrinidae) can fly through the air, swiftly swim on the surface of water, and quickly dive across the air-water interface. The propulsive efficiency of the species is believed to be one of the highest measured for a thrust generating apparatus within the animal kingdom. The goals of this research were to understand the distinctive biological mechanisms that allow the beetles to swim and dive, while searching for potential bio-inspired robotics applications. Through static and dynamic measurements obtained using a combination of microscopy and high-speed imaging, parameters associated with the morphology and beating kinematics of the whirligig beetle\u27s legs in swimming and diving were obtained. Using data obtained from these experiments, dynamics models of both swimming and diving were developed. Through analysis of simulations conducted using these models it was possible to determine several key principles associated with the swimming and diving processes. First, we determined that curved swimming trajectories were more energy efficient than linear trajectories, which explains why they are more often observed in nature. Second, we concluded that the hind legs were able to propel the beetle farther than the middle legs, and also that the hind legs were able to generate a larger angular velocity than the middle legs. However, analysis of circular swimming trajectories showed that the middle legs were important in maintaining stable trajectories, and thus were necessary for steering. Finally, we discovered that in order for the beetle to transition from swimming to diving, the legs must change the plane in which they beat, which provides the force required to alter the tilt angle of the body necessary to break the surface tension of water. We have further examined how the principles learned from this study may be applied to the design of bio-inspired swimming/diving robots. DOI: 10.1371/journal.pcbi.100279

Mini-/Micro-Scale Free Surface Propulsion

This work reports theoretical studies and experimental proofs of the propulsion of mini-/micro-scale floating objects that propel on air-liquid interface by using two different principles. The devices are extremely simple and do not include any moving parts. The first principle takes advantage of three-phase contact line oscillation that is activated by AC electrowetting on dielectric (EWOD) to propel the floating object. The capillary wave that is generated by the free surface oscillation is visualized by using the Free-Surface Synthetic Schlieren (FS-SS) method. A 3-D flow field sketch is constructed based on the flow visualizations and PIV measurements. The flow field and trajectories of seeded particles suggest that Stokes drift is the responsible mechanism for the propulsion. The propulsion speed of the floating object highly depends on the amplitude, frequency, and shape of the EWOD signal. These phenomena are also explained by the measured oscillation amplitudes and Stokes drift relations. Additionally, it is shown that a wider EWOD electrode generates a faster propelling speed. Finally, with stacked planar receiver coils and an amplitude modulated signal, a wirelessly powered AC EWOD propulsion is realized. The second principle of floating object propulsion is the Cheerios effect, which is also generally known as lateral capillary force. Four common physical configurations (interactions between two infinite vertical walls, two vertical circular cylinders, two spheres, and a sphere and a vertical wall) are reviewed. Through theoretical analysis, it has been revealed that not the wettability of the surface but the slope angle of the object is the most important parameter for the Cheerios effect. A general rule for this effect is that the lateral capillary force is attractive if the slope angles of the interacting objects have the same sign, otherwise the force is repulsive. In addition to the surface wettability, the size and the density of floating spheres are also important for the slope angle. Active control of the Cheerios effect is achieved by implementing EWOD and dielectrowetting methods to adjust the surface wettability. By sequentially activating micro-fabricated EWOD/dielectrowetting electrodes, linear translations of floating objects in the small scale channel are accomplished. A continuous rotational motion of the floating rod is achieved in a circular container by the EWOD method

Microfluidic bubble logic

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008."September 2008."Includes bibliographical references.In this thesis, I propose a new paradigm in computing where bits can simultaneously transport and manipulate materials and information. Information representation is invariably physical. Though this insight is fundamental to understanding the physical limits of computation, it has never been exploited as a scheme for material manipulation. Bringing together notions from computer science and fluid dynamics, I present a new logic family "Bubble Logic" capable of both universal computation and programmable material manipulation in an all-fluidic two-phase system. This removes the distinction between materials and mechanisms to control them, bringing the programmability of the digital world into the physical world - with a wide range of promising applications in biotechnology, highthroughput screening, genomics and fluidic control systems for soft robotics, printing and digital fabrication.Microfluidics, the art of handling nano-to pico-liter volume fluids, is leading to a revolution in large-scale automation of biology and analytical chemistry. However, current lab-on-chip technologies are dependent on external macro-scale control elements, thus requiring a lab to run the chip. Bubble logic provides a dropletel,internal, inherently digital flow control mechanism at kHz frequencies with no moving parts or off-chip components. Nonlinearity is introduced in an otherwise linear, reversible, low Reynolds number flow via bubble-tobubble hydrodynamic interactions. I demonstrate bubble logic AND/OR/NOT gates, a toggle flip-flop, a ripple counter, a timing restoration device, a ring oscillator, a bistable valve and an on-demand bubble generator. These show the nonlinearity, gain, bistability, synchronization, cascadability, feedback and programmability required for scalable universal computation and control.(cont.) The representation used in this thesis makes possible encapsulation and manipulation of a large variety of micro-to nanocale materials including single molecules like DNA or proteins, live cells, liquid crystals, nano-particles and other biological and chemical reagents. Bubble logic provides a scheme to transport, store and operate on this new class of "digital materials" in an integrated, high-throughput fashion. Furthermore, microfluidics has also been extensively employed in biological systems. This thesis describes the discovery of two new physical fluid dynamic mechanisms motivated by a common theme of microfluidics in biology. Firstly, I describe a new superhydrophobic waterrepelling surface that has a characteristic of directional anisotropy to fluid resistance. The discovery, made while studying the integument of water-walking insects, helps rationalize the origin of thrust and hence propulsion of water-walking insects on a fluid interface. Secondly, this thesis uncovers a new physical mechanism for directed droplet transport, which I term "Capillary ratchet". Discovered in a class of surface feeding shorebirds, it is the only physical mechanism that is known to exploit contact angle hysteresis for fluid transport. Capillary ratchet is a promising candidate for implementing global clocking for integrated microfluidic devices.by Manu Prakash.Ph.D

Tuning the interaction of droplets with liquid-repellent surfaces: fundamentals and applications

2018 Fall.Includes bibliographical references.Liquid-repellent surfaces can be broadly classified as non-textured surfaces (e.g., smooth slippery surfaces on which droplets can slide easily) and textured surfaces (e.g., super-repellent surfaces on which liquid droplets can bead up and roll off easily). The liquid repellency of smooth slippery surfaces can be adjusted by tuning the surface chemistry. The liquid repellency of super-repellent surfaces can be adjusted by tuning the surface chemistry and surface texture. In this work, by systematically tuning the surface chemistry and surface texture and consequently the surface wettability of solid surfaces, the interaction of droplets of various liquids on liquid-repellent surfaces has been investigated. Based on this understanding, the following phenomena/applications have been investigated/developed: (i New methodology to sort liquid droplets based on their surface tension: By tuning the surface chemistry and surface texture of solid surfaces, we tuned the mobility of liquids with different surface tension on super-repellent surfaces. Utilizing this, we fabricated a simple device with precisely tailored domains of surface chemistry that can sort droplets by surface tension. (ii) New approach to detect the quality of fuel blends: By tuning the surface chemistry of solid surfaces, we investigated the interaction of fuel blends with liquid-repellent surfaces. Based on the understanding gained, we fabricated a simple, field-deployable, low-cost device to rapidly detect the quality of fuel blends by sensing their surface tension with significantly improved resolution. (iii) Novel materials with improved hemocompatibility: By systematically tuning the surface chemistry and surface texture and consequently the surface wettability of solid surfaces, we investigated the interaction of blood with super-repellent surfaces. Based on the understanding gained, we fabricated super-repellent surfaces with enhanced hemocompatibility. (iv) Advanced understanding of droplet splitting upon impacting a macroscopic ridge: By systematically tuning the ridge geometry, we investigated the interaction of impacting water droplets with super-repellent ridges. Based on the understanding gained, we demonstrated the scaling law for predicting the height from which water droplets should fall under gravity onto a super-repellent ridge for them to split into two smaller droplets

Functional surface microstructures inspired by nature – From adhesion and wetting principles to sustainable new devices

In the course of evolution nature has arrived at startling materials solutions to ensure survival. Investigations into biological surfaces, ranging from plants, insects and geckos to aquatic animals, have inspired the design of intricate surface patterns to create useful functionalities. This paper reviews the fundamental interaction mechanisms of such micropatterns with liquids, solids, and soft matter such as skin for control of wetting, self-cleaning, anti-fouling, adhesion, skin adherence, and sensing. Compared to conventional chemical strategies, the paradigm of micropatterning enables solutions with superior resource efficiency and sustainability. Associated applications range from water management and robotics to future health monitoring devices. We finally provide an overview of the relevant patterning methods as an appendix

Functional surface microstructures inspired by nature : From adhesion and wetting principles to sustainable new devices

In the course of evolution nature has arrived at startling materials solutions to ensure survival. Investigations into biological surfaces, ranging from plants, insects and geckos to aquatic animals, have inspired the design of intricate surface patterns to create useful functionalities. This paper reviews the fundamental interaction mechanisms of such micropatterns with liquids, solids, and soft matter such as skin for control of wetting, self-cleaning, anti-fouling, adhesion, skin adherence, and sensing. Compared to conventional chemical strategies, the paradigm of micropatterning enables solutions with superior resource efficiency and sustainability. Associated applications range from water management and robotics to future health monitoring devices. We finally provide an overview of the relevant patterning methods as an appendix

Micro/Nano Structures and Systems

Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability is a comprehensive guide that explores the various aspects of micro- and nanostructures and systems. From analysis and design to manufacturing and reliability, this reprint provides a thorough understanding of the latest methods and techniques used in the field. With an emphasis on modern computational and analytical methods and their integration with experimental techniques, this reprint is an invaluable resource for researchers and engineers working in the field of micro- and nanosystems, including micromachines, additive manufacturing at the microscale, micro/nano-electromechanical systems, and more. Written by leading experts in the field, this reprint offers a complete understanding of the physical and mechanical behavior of micro- and nanostructures, making it an essential reference for professionals in this field