The Pennsylvania State University The Graduate School Department of Chemistry CATALYTIC NANOMOTORS AND MICROPUMP SYSTEMS UTILIZING ALTERNATE FUELS A Dissertation in Chemistry by Flory K. Wong © 2016 Flory K. Wong Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy December 2016 ii The dissertation of Flory K. Wong was reviewed and approved* by the following: Ayusman Sen Distinguished Professor of Chemistry Dissertation Advisor Chair of Committee Thomas E. Mallouk Evan Pugh University Professor of Chemistry, Biochemistry, Molecular Biology, and Physics Head of the Department of Chemistry Raymond E. Schaak DuPont Professor of Materials Chemistry Darrell Velegol Distinguished Professor of Chemical Engineering *Signatures are on file in the Graduate School. iii ABSTRACT Colloidal assemblies of self-powered active particles have become a focus area of research. Ranging from microscopic particle suspensions to nanoscale molecules, these systems transduce chemical energy into mechanical motion across multiple length scales following a variety of mechanisms. Understanding the energy transduction processes and the subsequent nature of particle dynamics offers unprecedented opportunities to explore the physics of small-scale colloidal systems and to harness their behavior in many useful applications. However, over a decade after the initial discovery of autonomous bimetallic nanorods, we continue to struggle to bring such systems into real-world applications. Part of the setback has been the in-depth research into hydrogen peroxide fuel. While the studies have built up the fundamental knowledge necessary for the advancement of the field, we have yet to do the same for other systems that employ alternate fuels. This dissertation aims to fill that void by developing nano- and micromotor and pump systems that does not rely on traditional hydrogen peroxide fuel, uses novel material by taking inspiration in other areas of research, and complete in-depth studies to provide a clear understanding of such systems. Chapter 1 provides a general overview of the research into chemically powered nano- and micromotors and pumps, the motivation behind my interest, and concise descriptions of the individual research projects discussed in this dissertation. Chapter 2 and 3 discusses a highly efficient silver-based nanomotor and micropump system that operates in iodine media. It is a significant step in the development of a new type of system as it is extremely efficient in fuel conversion as well as being a light-modulated system. iv Chapter 4 utilizes an established biopolymer to fabricate an acid-sensitive micropump and a proof-of-concept micromotor. This work provides the fundamentals that can be applied to converting other types of polymer into active colloidal systems. Chapter 5 puts forth a novel biodegradable dual-mechanism micropump made of zinc and iron. The pump is controlled by both electrokinetics and density driven flows. This new system is undaunted by high electrolyte environments and is not limited to one type of chemical fuel, as it is capable of fluid pumping in acid, salt, and buffered solutions. This dissertation concludes with a brief perspective on the future advancement in nano- and micromachine development. v Table of Contents LIST OF FIGURES ................................................................................................................................... viii LIST OF TABLES ..................................................................................................................................... xiii ACKNOWLEDGEMENTS ....................................................................................................................... xiv EPIGRAPH ................................................................................................................................................ xvi Chapter 1 Introduction .................................................................................................................................. 1 1.1 Background ......................................................................................................................................... 1 1.2 Development of catalytic motor and pump systems ........................................................................... 4 1.3 Motor and pump systems utilizing alternate fuels .............................................................................. 5 1.4 Research motivation ............................................................................................................................ 6 1.5 References ........................................................................................................................................... 9 Chapter 2 Highly efficient light-harvesting nanomotor using halogen media ............................................ 16 2.1 Introduction ....................................................................................................................................... 16 2.2 Experimental details .......................................................................................................................... 18 2.2.1 Fabrication ................................................................................................................................. 18 2.2.2 Experimental setup ..................................................................................................................... 19 2.2.3 Characterization ......................................................................................................................... 20 2.3 Autonomous motion of Ag-based Nanomotors ................................................................................ 21 2.3.1 Directed linear motion of nanorods............................................................................................ 21 2.3.2 Motor Characterization .............................................................................................................. 22 2.3.3 Mechanism ................................................................................................................................. 31 2.3.4 Nanomotor Efficiency ................................................................................................................ 33 2.4 Light-harvesting effect of silver-based nanomotors ......................................................................... 35 2.4.1 Regeneration of silver via light exposure................................................................................... 35 2.4.2 Phenomena ................................................................................................................................. 36 2.5 Collective behavior in Silver-based nanomotors .............................................................................. 40 2.5.1 Introduction ................................................................................................................................ 40 2.5.2 Fabrication and Experimental details ......................................................................................... 42 2.5.3 Characterization of Schools ....................................................................................................... 43 2.5.4 Light-modulated effects on collective behavior ......................................................................... 46 2.5.5 Mechanism ................................................................................................................................. 47 2.6 Conclusion ........................................................................................................................................ 49 2.7 References ......................................................................................................................................... 50 Chapter 3 Light-modulated silver-based micropump using micromolar halogen media ............................ 53 vi 3.1 Introduction ....................................................................................................................................... 53 3.2 Experimental details .......................................................................................................................... 55 3.2.1 Fabrication ................................................................................................................................. 55 3.2.2 Experimental setup ..................................................................................................................... 55 3.3 Fluid and particle motion in silver-based halogen micropump ......................................................... 57 3.3.1 Analysis of particle/fluid motion ............................................................................................... 57 3.3.2 Mechanism ................................................................................................................................. 60 3.3.3 Light-modulated effect of micropumps ..................................................................................... 61 3.4 Conclusion ........................................................................................................................................ 63 3.5 References ......................................................................................................................................... 64 Chapter 4 Biocompatible acetalated dextran polymer micromotor and pumps .........................................