This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON AUTOMATION SCIENCE AND ENGINEERING 1 AFAM: An Articulated Four Axes Microrobot for Nanoscale Applications Rakesh Murthy, Member, IEEE, Harry E. Stephanou, Member, IEEE, and Dan O. Popa Abstract—This paper presents a microassembled robot called the Articulated Four Axes Microrobot (AFAM). Target applica- tion areas include micro and nano part manipulation and probing. The robot consists of a cantilever actuated along four axes: in-place and ; out-of-plane pitch. The microrobot size spans a total volume of ( ), and oper- ates within a workspace envelope of ( ). This is by far the largest operating envelope of any mi- cropositioner with nonplanar dexterity. As a result it can be clas- sified as a new type of three-dimensional microrobot and a candi- date for miniaturizing top-down assembly systems to dimensions under . A key feature in this design is a cable-like microwire that transforms in-plane actuator displacement into out-of-plane pitch and yaw motion (via flexure joints). Finite-element analysis simulation followed by microfabrication and assembly processes developed to prototype the designs are described. The microrobot is designed to carry an AFM tip as the end effector and accomplish nanoindentation on a polymer surface. The tip attachment tech- nique and nanoindentation experiments have also been described in this paper. Open loop precision has been characterized using a laser interferometer which measured an average resolution of 50 nm along , repeatability of 100 nm and accuracy of 500 nm. Experiments to determine microrobot reliability are also pre- sented. Note to Practitioners—Micro/nanosystems research and de- velopment incorporates a large variety of tools and processes in order to accomplish high precision fabrication, assembly, testing and characterization. A very common component in these tools is high precision positioning units (robots) that are a combination of linear and rotary subunits (stages). Their role is to position micro or nanocomponents, substrates or wafers in an accurately and repeatable manner. Current state-of-art positioners typically span few inches to many feet in size. Although they are able to deliver the required precision, range of motion, and dexterity, their size inhibits the merger of multiple units under a common platform leading to throughput limitations. This paper presents an attempt to develop a new class of miniaturized robots that span no more than a few cubic millimeters in size, while delivering a subset of the capabilities as traditional macroscale equivalents. The tradeoffs between robot size, stiffness, range of motion, dexterity, and precision is taken to a new level where the robots are no more than two or three orders of magnitude larger than the smallest parts being manufactured. Manuscript received October 15, 2011; revised March 09, 2012; accepted May 12, 2012. This paper was recommended for publication by Associate Editor Z. Wang and Editor K. Bohringer upon evaluation of the reviewers’ comments. This work was supported by the Office of Naval Research and carried out at Au- tomation and Robotics Research Institute, the University of Texas at Arlington. R. Murthy is with the Nano and Micro Systems Group, Instrument Electronics and Sensors Division, Jet Propulsion Laboratory, Passadena, CA 91109 USA (e-mail: rakesh.murthy@jpl.nasa.gov). D. O. Popa and H. Stephanou are with the University of Texas at Arlington, Arlington, TX 76011 USA (e-mail: popa@arri.uta.edu). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TASE.2012.2217740 Index Terms—Microassembly, microelectromechanical systems (MEMS), microrobot. I. INTRODUCTION R OBOTIC handling can play a critical role in the advance- ment of nanotechnology and has been a popular research topic for the last decade [1]–[3]. Currently at tens-of-nanome- ters size scales, bottom-up self-assembly processes are the main driving mechanisms for controlled aggregation of nanoparts [4], [5]. Although self-assembly promises high throughput, the resulting assembled components are usually axisymmetric and of a single composition. As an alternative technique, top-down manipulation using serial or parallel manipulation [6], [7] holds promise to produce heterogeneous and complex nano/micro assemblies. The drawback with serial assembly is limited throughput. Recently, researchers have proposed hybrid (top-down and bottom-up) nanoscale assembly approaches to take advantage of the best characteristics of both methods [8], [9]. High precision positioning and sensing systems such as atomic force microscopes (AFM) and robot integrated scan- ning electron microscopes (SEM) have offered a critical path towards nanoscale manufacturing [10]–[12]. They facilitate probing, gripping, pushing and scanning tasks. Such hardware are typically many orders of magnitude larger than the size of the parts they manipulate. [10]. As useful as they can be, AFM’s operate in a serial sensing or manipulating mode. With advances in Microelectromechanical Systems (MEMS), new types of smaller positioning devices can be designed for nanoscale manipulation, probing and force measurement, optical microsystems, and high density data storage devices [13]–[15]. The systems described in references [13]–[15] are most relevant in comparison to the design presented in this manuscript. The design of such positioners must bal- ance performance parameters such as range of motion, force output/payload capacity, and dexterity (degrees of freedom). Due to 2-½ D geometries, these have limited out-of-plane displacement outputs (e.g., mostly planar dexterity). MEMS positioners with more than 3 degrees of freedom have been fabricated using thin-film deposition and etching, but have limited force outputs, payload capacities, and reliability to operate as independent micromanipulators [15]. Due to these inherent tradeoffs, MEMS devices have been used as grippers or force sensors in conjunction with larger con- ventional positioning stages, and therefore the overall dimen- sions of the manipulator spans several inches [16], [17]. This limits in applications requiring multiple such positioners within confined volumes, for example, inside a transmission electron U.S. Government work not protected by U.S. copyright.