277 9 Design of Optically Driven Microrotors Halina Rubinsztein-Dunlop, Theodor Asavei, Alex Stilgoe, Vince Loke, Timo Nieminen, and Norman Heckenberg 9.1 INTRODUCTION 9.1.1 MICROMACHINES Richard Feynman anticipated the idea of micromachines in his 1959 talk, “There’s plenty of room at the bottom” (Feynman 1960). Feynman suggested as a possible micromachine a micromechanical “surgeon,” which could be swallowed and operate inside a faulty blood vessel. At the end of his talk Feynman offered two prizes, one for building an operating electric motor only the size of a 1/64in. 3 and the other for writing a page with letters 1/25,000 smaller than in normal text. Not long after, in CONTENTS 9.1 Introduction .......................................................................................................................... 277 9.1.1 Micromachines ......................................................................................................... 277 9.1.2 Drive Mechanisms for Micromachines .................................................................... 278 9.1.3 Phase Singular Fields and Orbital Angular Momentum .......................................... 278 9.1.4 Symmetry and Optically Driven Micromachines .................................................... 279 9.1.5 Experimental Setup .................................................................................................. 281 9.2 Microrotors Driven by Spin Angular Momentum ................................................................ 283 9.2.1 Design and Microfabrication of Form Birefringent “Holey” Microspheres............. 283 9.2.2 Rotation in Optical Tweezers.................................................................................... 285 9.2.3 Functionalization with Biomolecules ....................................................................... 288 9.3 Microrotors Driven by Orbital Angular Momentum............................................................ 289 9.3.1 Optically Driven Chiral Microrotor ......................................................................... 289 9.3.1.1 Design and Microfabrication ..................................................................... 289 9.3.1.2 Rotation in Optical Tweezers ..................................................................... 291 9.3.1.3 Discussion .................................................................................................. 292 9.3.2 Measuring Optical Angular Momentum Transfer to Optically Driven Microrotors .................................................................................................. 293 9.3.2.1 Design and Microfabrication ..................................................................... 294 9.3.2.2 Rotation and Performance in Optical Tweezers ........................................ 294 9.3.2.3 Discussion .................................................................................................. 295 9.4 Optically Driven Microscopic Paddle-Wheel ....................................................................... 300 9.4.1 Motivation ................................................................................................................. 300 9.4.2 Design and Microfabrication .................................................................................... 300 9.4.3 Paddle-Wheel Optical Rotation ................................................................................ 300 9.4.4 Discussion ................................................................................................................. 303 9.5 Summary and Conclusion..................................................................................................... 304 References ...................................................................................................................................... 305 K11879_C009.indd 277 7/20/2012 7:06:41 PM