Full text available at: http://dx.doi.org/10.1561/2300000023 Micro-Scale Mobile Robotics Full text available at: http://dx.doi.org/10.1561/2300000023 Micro-Scale Mobile Robotics Eric Diller Carnegie Mellon University Pittsburgh, PA 15213 USA [email protected] Metin Sitti Carnegie Mellon University Pittsburgh, PA 15213 USA [email protected] Boston { Delft Full text available at: http://dx.doi.org/10.1561/2300000023 Foundations and Trends R in Robotics Published, sold and distributed by: now Publishers Inc. PO Box 1024 Hanover, MA 02339 USA Tel. +1-781-985-4510 www.nowpublishers.com [email protected] Outside North America: now Publishers Inc. PO Box 179 2600 AD Delft The Netherlands Tel. +31-6-51115274 The preferred citation for this publication is E. Diller and M. Sitti, Micro-Scale Mobile Robotics, Foundations and Trends R in Robotics, vol 2, no 3, pp 143{259, 2011. ISBN: 978-1-60198-710-5 c 2013 E. Diller and M. Sitti All rights reserved. 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Please apply to now Publishers, PO Box 179, 2600 AD Delft, The Netherlands, www.nowpublishers.com; e-mail: [email protected] Full text available at: http://dx.doi.org/10.1561/2300000023 Foundations and Trends R in Robotics Volume 2 Issue 3, 2011 Editorial Board Editor-in-Chief: Henrik Christensen Georgia Institute of Technology United States Roland Siegwart ETH Zurich Switzerland Editors Minoru Asada (Osaka University) Simon Lacroix (LAAS) Antonio Bicchi (University of Pisa) Christian Laugier (INRIA) Aude Billard (EPFL) Steve LaValle (UIUC ) Cynthia Breazeal (MIT ) Yoshihiko Nakamura (The University Oliver Brock (TU Berlin) of Tokyo) Wolfram Burgard (University Brad Nelson (ETH ) of Freiburg) Paul Newman (Oxford University) Udo Frese (University of Bremen) Daniela Rus (MIT ) Ken Goldberg (UC Berkeley) Giulio Sandini (University of Genova) Hiroshi Ishiguro (Osaka University) Sebastian Thrun (Stanford) Makoto Kaneko (Osaka University) Manuela Veloso (Carnegie Mellon Danica Kragic (KTH ) University) Vijay Kumar (University of Markus Vincze (Vienna University) Pennsylvania) Alex Zelinsky (CSIRO) Full text available at: http://dx.doi.org/10.1561/2300000023 Editorial Scope Foundations and Trends R in Robotics publishes survey and tutorial articles in the following topics: • Foundations • Planning and Control ◦ Mathematical modelling ◦ Control of manipulation systems ◦ Kinematics ◦ Control of locomotion systems ◦ Dynamics ◦ Behaviour based systems ◦ Estimation Methods ◦ Distributed systems ◦ Robot Control ◦ Multi-Robot Systems ◦ Planning • Human-Robot Interaction ◦ Artificial Intelligence in Robotics ◦ Robot Safety ◦ Software Systems and ◦ Physical Robot Interaction Architectures ◦ Dialog Systems • Mechanisms and Actuators ◦ Interface design ◦ Kinematic Structures ◦ Social Interaction ◦ Legged Systems ◦ Teaching by demonstration ◦ Wheeled Systems • Industrial Robotics ◦ Hands and Grippers ◦ Welding ◦ Micro and Nano Systems ◦ Finishing • Sensors and Estimation ◦ Painting ◦ Force Sensing and Control ◦ Logistics ◦ Haptic and Tactile Sensors ◦ Assembly Systems ◦ Proprioceptive Systems ◦ Electronic manufacturing ◦ Range Sensing • Service Robotics ◦ Robot Vision ◦ Professional service systems ◦ Visual Servoing ◦ Domestic service robots ◦ Localization, Mapping and SLAM ◦ Field Robot Systems ◦ Medical Robotics Information for Librarians Foundations and Trends R in Robotics, 2011, Volume 2, 4 issues. ISSN paper version 1935-8253. ISSN online version 1935-8261. Also available as a combined paper and online subscription. Full text available at: http://dx.doi.org/10.1561/2300000023 Foundations and Trends R in Robotics Vol. 2, No. 3 (2011) 143{259 c 2013 E. Diller and M. Sitti DOI: 10.1561/2300000023 Micro-Scale Mobile Robotics Eric Diller1 and Metin Sitti2 1 Carnegie Mellon University, NanoRobotics Lab, Department of Mechanical Engineering, Pittsburgh, PA 15213, USA, [email protected] 2 Carnegie Mellon University, NanoRobotics Lab, Department of Mechanical Engineering, Pittsburgh, PA 15213, USA, [email protected] Abstract The field of microrobotics has seen tremendous advances in recent years. The principles governing the design of such submillimeter scale robots rely on an understanding of microscale physics, fabrication, and novel control strategies. This monograph provides a tutorial on the relevant physical phenomena governing the operation and design of microrobots, as well as a survey of existing approaches to microrobot design and control. It also provides a detailed practical overview of actuation and control methods that are commonly used to remotely power these designs, as well as a discussion of possible future research directions. Potential high-impact applications of untethered micro- robots such as minimally invasive diagnosis and treatment inside the human body, biological studies or bioengineering, microfluidics, desk- top micromanufacturing, and mobile sensor networks for environmental and health monitoring are reported. Full text available at: http://dx.doi.org/10.1561/2300000023 Contents 1 Introduction 1 1.1 Brief History of Microrobotics 3 2 Microscale Challenges 9 2.1 Microscale Physics and Dynamics 9 2.2 Energy Requirements 25 2.3 Microrobot Fabrication 29 3 Approaches 35 3.1 Actuation Methods 35 3.2 Microrobot Locomotion Methods 50 3.3 Buoyancy 66 3.4 Microrobot Localization 68 3.5 Multi-Robot Control 71 4 Potential Applications 81 4.1 Microobject Manipulation 81 4.2 Healthcare 89 4.3 Reconfigurable Microrobotics 90 4.4 Scientific Tools 93 ix Full text available at: http://dx.doi.org/10.1561/2300000023 5 Conclusions and Open Challenges 95 5.1 Status Summary 95 5.2 What Next? 96 5.3 Conclusions 98 Nomenclature 99 References 103 Full text available at: http://dx.doi.org/10.1561/2300000023 1 Introduction Due to recent advances in micro- and nanoscale science and technol- ogy and increasing demand for new microsystems for applications in medicine, biotechnology, manufacturing, and mobile sensor networks, creating tiny mobile robots that could access enclosed small spaces down to the micron scale such as inside the human body and microflu- idic devices and could manipulate and interact with micro/nanoscale entities has become a critical issue. Since human or macroscale robot sensing, precision, and size are not sufficient to interact with such tiny objects and access such tiny spaces directly, microrobotics has emerged as a new robotics field to extend our interaction and exploration capa- bilities to submillimeter scales. Moreover, mobile microrobots could be manufactured cost-effectively in large numbers where a large number of microrobots could enable new massively parallel, self-organizing, recon- figurable, swarm, or distributed systems. For these purposes, many groups have been proposing various untethered mobile microrobotic systems in the past decade. Such untethered microrobots could enable many new applications such as minimally invasive diagnosis and treat- ment inside the human body, biological studies or bioengineering applications inside microfluidic channels, desktop micromanufacturing, and mobile sensor networks for environmental and health monitoring. 1 Full text available at: http://dx.doi.org/10.1561/2300000023 2 Introduction There is no standardized definition of the term microrobot. In fact, reported microrobots range in size from single µms to the cm scale. However, one common approach defines a microrobot as existing in the size range of hundreds of nm to 1 mm. In some cases, component size scale being micron scale is taken as the crucial aspect, which could then include millimeter or centimeter-scale mobile robots as microrobots. In other cases, overall size scale being micron scale is emphasized where mobile robots able to fit in spaces smaller than a millimeter are con- sidered as microrobots. In this monograph, the latter is used to define microrobots since the overall size dictates the environment in which the robots are capable of accessing, and also tells us something about their capabilities. On the other hand, a more relevant definition when studying novel wireless locomotion schemes might involve the types of physical interactions which dominate the motion and interaction of the robot. Large or centi/milli-scale robots are dominated by inertial