Design, fabrication and control of soft robots

Conventionally, engineers have employed rigid materials to fabricate precise, predictable robotic systems, which are easily modelled as rigid members connected at discrete joints. Natural systems, however, often match or exceed the performance of robotic systems with deformable bodies. Cephalopods, for example, achieve amazing feats of manipulation and locomotion without a skeleton; even vertebrates such as humans achieve dynamic gaits by storing elastic energy in their compliant bones and soft tissues. Inspired by nature, engineers have begun to explore the design and control of soft-bodied robots composed of compliant materials. This Review discusses recent developments in the emerging field of soft robotics.National Science Foundation (U.S.) (Grant IIS-1226883

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

Integrated Control of Microfluidics – Application in Fluid Routing, Sensor Synchronization, and Real-Time Feedback Control

Microfluidic applications range from combinatorial chemical synthesis to high-throughput screening, with platforms integrating analog perfusion components, digitally controlled microvalves, and a range of sensors that demand a variety of communication protocols. A comprehensive solution for microfluidic control has to support an arbitrary combination of microfluidic components and to meet the demand for easy-to-operate system as it arises from the growing community of unspecialized microfluidics users. It should also be an easy to modify and extendable platform, which offer an adequate computational resources, preferably without a need for a local computer terminal for increased mobility. Here we will describe several implementation of microfluidics control technologies and propose a microprocessor-based unit that unifies them. Integrated control can streamline the generation process of complex perfusion sequences required for sensor-integrated microfluidic platforms that demand iterative operation procedures such as calibration, sensing, data acquisition, and decision making. It also enables the implementation of intricate optimization protocols, which often require significant computational resources. System integration is an imperative developmental milestone for the field of microfluidics, both in terms of the scalability of increasingly complex platforms that still lack standardization, and the incorporation and adoption of emerging technologies in biomedical research. Here we describe a modular integration and synchronization of a complex multicomponent microfluidic platform

System Integration - A Major Step toward Lab on a Chip

Microfluidics holds great promise to revolutionize various areas of biological engineering, such as single cell analysis, environmental monitoring, regenerative medicine, and point-of-care diagnostics. Despite the fact that intensive efforts have been devoted into the field in the past decades, microfluidics has not yet been adopted widely. It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics. In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications. Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications

Physics and Applications of a PDMS Based Centrifugal Microfluidic System

The objective of this research work is to develop a centrifugal microfluidic system for general purposes based on microfabrication technologies including SU-8 photolithography, polydimethylsiloxane (PDMS) casting. The main contribution of this research is to integrate a flyball governor system into the polymer based centrifugal microfluidic platform. A series of function units are developed based on this unique mechanism. In the first part, three pinch valve systems were designed and tested. The first one is based on the magnetic force and the second one is on the basis of spring force and the last one is a membrane valve. All valving system demonstrate good control of the fluid movement. The latter two valves are capable of sequential control. It proves that the flyball governor system is very compatible with centrifugal fluidic technologies. The major advantage of this new actuation technology is that its burst frequency can be conveniently manipulated by adjusting the parameters of the mechanical system without changes in the fluidic pattern. Next, two types of inward pumping systems were designed and tested. The result shows that both the inward pumps were capable of the pumping over a radial distance of 21mm in a short time. It thus improves the usage of space on the disc and paves the way to interconnect several functional units. Then as a proof of concept, a sequential valving system capable of metering and centrifugal sediment was developed for plasma extraction from whole blood. The resulting residual cell concentration was less than 0.5%. In the last part, a micromixer was developed based on the similar principle. The results show that the flyball governor system can effectively agitate the chaotic mixing of the sample liquids by periodically deflecting the PDMS membrane of the mixing chamber. The mixing effect can thus be enhanced

Large Array of Shape Memory Polymer Actuators for Haptics and Microfluidics

My thesis advances the field of shape memory polymer (SMP) actuators by providing a versatile strategy to arbitrarily reconfigure large arrays of densely packed latching soft actuators. It exploits two key intrinsic characteristics of SMPs, which are their multistable nature and their drastic change in Young¿s modulus with temperature, to combine both actuation plus latching in a single actuator. The novel concept consists in individually and selectively addressing arrays of SMP actuators by synchronizing their local Joule heating with a single common air pneumatic supply. Stretchable heaters are integrated and patterned on thin SMP membranes in order to precisely define regions where the stiffness can be changed by over two orders of magnitude. By a timely synchronization of the thermal stimuli with the external air pressure, each actuator can be independently, reversibly, and rapidly latched into any positions. The potential of coupling local Joule heating with global air pneumatic actuation for large arrays of SMP actuators is demonstrated by a 32x24 flexible haptic display and by a 4x4 microfluidic platform. The active layer of the SMP actuator is made of a commercially available SMP material for the SMP membrane and a mixture of carbon black (CB) with soft polydimethylsiloxane (PDMS) for the stretchable heating electrodes. The final SMP actuator geometry corresponds to the best trade-off between displacement and holding force for both haptic and microfluidic applications. The 32x24 flexible haptic display is the first high resolution wearable sleeve capable to vary its surface topology. This device consists of a 40 µm thick SMP membrane, on which a matrix of 25 µm thick stretchable heaters on 4 mm pitch is integrated, interconnected by a 4-layers flexible printed circuit board (PCB) and bonded to a stretchable 3D-printed pneumatic chamber. Each tactile pixel (taxel) can be individually controlled via row/column addressing, requires 250 mW to heat up from 20 °C to 70 °C, and takes 2.5 s to latch to a different state. Each line (row or column) of taxels consumes at most 8 W and the entire haptic display is refreshed in under 1 min 30 s. The haptic display weighs only 55 g and is 2 mm thick. More than 99 % of the 768 taxels are fully functional, with a lifetime in excess of 20000 cycles. The perception tests conducted on the 4x4 tactile tablet with 15 blindfolded sighted users resulted in 98 % correct pattern recognition in less than 10 s exploration, confirming that my SMP actuators are a promising taxel technology. The 4x4 microfluidic platform is the first latching microfluidic array where each valve is directly controlled with a common air pneumatic supply. Its active layer consists of a 50 µm thick SMP membrane, a matrix of 25 µm thick stretchable heaters, and a 37.5 µm thick styrene ethylene butylene styrene (SEBS) membrane. The actuators are electrically interconnected and mechanically bonded to a PCB. On the bottom, a polymethyl methacrylate (PMMA) pneumatic chamber is sealed and, on the top, a micromachined polystyrene (PS) microfluidic chip is bonded. The similarity in design for both normally closed (NC) and normally open (NO) valves enables to implement them in the same chip. These 3 mm in diameter valves remain closed up to 70 mbar of pressure before opening, validating that my SMP actuators are an interesting valve-unit for micropumps, mixers, and multiplexers in microfluidic large scale integration (mLSI) systems

Practical control methods for vacuum driven soft actuator modules

Vacuum-powered Soft Pneumatic Actuator (VSPA) Modules have been described to afford advantages for rapid development of reconfigurable, multi-DoF soft pneumatic robots powered by vacuum by reducing their logistical complexity, however they also present new challenges in the control of resulting systems. This framework features modules joined together over a simple embedded pneumatic and serial communication network and requires a unique approach to both low-level control implementation and high-level control strategy. We describe the structure and activation characteristics of a V-SPA Module and present practical methods for its control. These methods utilize software generated PWM activation through a unique serial protocol designed for LED networks and a heuristic mapping strategy for simplifying the spherical control of 3-DoF actuator modules

A lifting and actuating unit for a planar nanoprecision drive system

Ein wesentlicher Treiber in vielen heutigen Technologiebereichen ist die Miniaturisierung von elektrischen, optischen und mechanischen Systemen. Mehrachsige Geräte mit großen Verfahrbereichen und extremer Präzision spielen dabei nicht nur in der Messung und Qualitätssicherung, sondern auch in der Fabrikation und Manipulation von Nanometerstrukturen eine entscheidende Rolle. Die vertikale Bewegungsaufgabe stellt eine besondere Herausforderung dar, da die Schwerkraft des bewegten Objektes permanent kompensiert werden muss. Diese Arbeit schlägt dafür eine Vertikalhub- und -aktuiereinheit vor und trägt damit zur Weiterentwicklung von Nanometer-Präzisionsantriebssystemen bei. Grundlegende mögliche kinematische Integrationsvarianten werden betrachtet und entsprechend anwendungsrelevanter Kriterien gegenübergestellt. Der gezeigte parallelkinematische Ansatz zeichnet sich durch seine gute Integrierbarkeit, geringe negative Einflüsse auf die umliegenden Systeme, sowie die Verteilung der Last auf mehrere Stellglieder aus. Folgend wird ein konstruktiver Entwicklungsprozess zusammengestellt, um diese favorisierte Variante weiter auszuarbeiten. Im Laufe dieses Prozesses wird die zu entwickelnde Einheit in das Gesamtsystem eingeordnet und ihre Anforderungen, Randbedingungen und enthaltenen Teilsysteme definiert. Die vertikale Aktuierung besteht dabei aus zwei Systemen: Einer pneumatische Gewichtskraftkompensation und einem elektromagnetischen Präzisionsantrieb. Das technische Prinzip der Hubeinheit wird erstellt und die Teilsysteme im verfügbaren Bauraum angeordnet. Daraus wird ein detailliertes Modell des pneumatischen Aktors abgeleitet, dieser dimensioniert und dessen Eigenschaften bestimmt. Die Ausdehnung dieses Teilsystems definiert die räumlichen Grenzen für den umliegenden Präzisionsantrieb. Zur Auslegung dieses Antriebs wird das Kraft-/Leistungsverhältnis als Zielgröße definiert. Mit Hilfe von numerischer Simulation und Optimierung werden Geometrien für verschiedenste Topologien entworfen und bewertet. Die geeignetste Variante wird mit allen Teilsystemen in eine Einheit integriert und auskonstruiert. Abschließend werden zukünftige Schritte für die Integration der Einheit in ein Präzisionsantriebssystem dargestellt und mögliche Anwendungsszenarien in der Nanofabrikation präsentiert.A central driver in many of today's fields of technology is the miniaturization of electrical, optical and mechanical systems. Multi-axis devices with large travel ranges and extreme precision play a decisive role, not only in measurement and quality assurance, but also in the fabrication and manipulation of nanometer structures. The vertical movement task poses a special challenge, since the gravitational load of the moving object must be compensated permanently. This thesis proposes a vertically lifting and actuating unit and thus contributes to the further development of nanometer precision drive systems. Basic possible kinematic integration variants are considered and compared according to application relevant criteria. The presented parallel kinematic approach is characterized by its good integrability, its minimal negative influences on the surrounding systems, as well as the distribution of the load to several actuators. Subsequently, a constructive development process is compiled to further develop this favoured variant. During this process the unit to be developed is integrated into the overall system. Further, its requirements, boundary conditions and subsystems are defined. The vertical actuation consists of two systems: A pneumatic weight force compensation and an electromagnetic precision drive. The technical principle of the lifting unit is developed and the subsystems are arranged in the available design space. Based on this, a detailed model of the pneumatic actuator is created, its dimensions derived and properties obtained. These dimensions define the spatial limits for the surrounding precision actuator. For the design of this actuator, the force-power ratio is chosen as the objective quantity. Using numerical simulations and optimization, geometries for various topologies are created and evaluated. The most suitable variant is designed and integrated with all other subsystems into one unit. Finally, upcoming steps for integrating the unit into a precision drive system are outlined and possible future applications in the field of nanofabrication are presented

A Characterization of Actuation Techniques for Generating Movement in Shape-Changing Interfaces

Abstract This article characterizes actuation techniques for generating movement in shape-changing displays with physically reconfigurable geometry. To date, few works in Human Computer Interaction literature provide detailed and reflective descriptions of the implementation techniques used in shape-changing displays. This hinders the rapid development of novel interactions as researchers must initially spend time understanding technologies before prototyping new interactions and applications. To bridge this knowledge gap, we propose a taxonomy that classifies actuator characteristics and simplifies the process for designers to select appropriate technologies that match their requirements for developing shape-displays. We scope our investigation to linear actuators that are used in grid configurations. The taxonomy is validated by (a) examining current implementation techniques of motorized, pneumatic, hydraulic, magnetic, and shape-memory actuators in the literature, (b) constructing prototypes to address limited technical details and explore actuator capabilities in depth, (c) describing a use-case scenario through a case study that details the construction of a 10 ? 10 actuator shape-display, and (d) a set of guidelines to aid researchers in selecting actuation techniques for shape-changing applications. The significance of our taxonomy is twofold. First, we provide an original contribution that enables HCI researchers to appropriately select actuation techniques and build shape-changing applications. This is situated amongst other past works that have investigated broader application scenarios such as a shape-changing vocabulary, a framework for shape transformations, material properties, and technical characteristics of various actuators. Second, we carry out in-depth investigations to validate our taxonomy and expand the knowledge of vertical actuation in shape-changing applications to enable rapid development