AVS 60th International Symposium and Exhibition
    Accelerating Materials Discovery for Global Competitiveness Focus Topic Friday Sessions
       Session MG+AS+EM+NS+SA+SE+SP+SS+TF-FrM

Paper MG+AS+EM+NS+SA+SE+SP+SS+TF-FrM5
Catalytic Micro-/Nano- Motors Propelled by Bubbles

Friday, November 1, 2013, 9:40 am, Room 202 B

Session: Novel Synthesis Approaches and Innovative Characterization Techniques Coupled with Theory & Computations
Presenter: M.T. Manjare, University of Georgia, Athens
Authors: M.T. Manjare, University of Georgia, Athens
B. Yang, University of Texas, Arlington
Y.P. Zhao, University of Georgia, Athens
Correspondent: Click to Email
Catalytic Micromotors are micro- or nano- objects that use catalytic reaction, most commonly H2O2 --> H2O + 1/2 O2, to propel themselves in fluid environment. The motion of the motors can be controlled by designing different motor geometries and functionalizations and to perform variety of tasks such as cargo towing and biosensing. One of the mechanisms by which the motors move is bubble propulsion, i.e., the O2 generated in the reaction forms bubbles and propel the motors by ejecting or bursting the bubbles. Bubble propulsion is proven to be the most efficient and fastest way to drive the motors. Here we report our new discoveries on bubble propelled catalytic motors. For spherical particles, electron beam evaporation method is used to coat half of their surface with Pt and to make them as Janus motors. A new bubble propelled quasioscillatory translational motion is observed only for big motors. The motion coincided with bubble growth and burst resulting from catalytic reaction. A physical model was proposed which explained that bubble growth imparts a growth force on the motor to move it forward and instantaneous local pressure depression due to bubble burst causes the motor to move backward. The competition of the two processes generates a net forward motion. The bubble propulsion mechanism involves hydrodynamics, growth kinetics, and mass/momentum transport. In order to understand the detailed mechanism, we have investigated the mass transport in microtubular jet engines, a major bubble propelled motor. A one dimensional mass transport model using basic principles of diffusion and reaction is built to explain the effect of environmental factors such as fuel concentration and of geometry on the motion. Numerical investigations of the motion-related parameters, such as O2 flux, bubble generation rate and frequency, and average speed of the microjet motors during bubble growth, are found to depend closely on the length and opening radius of the microjet and the concentration of H2O2 in the surrounding environment. The theoretical results are in good agreement with the motion of Graphene oxide tubular microjet motors we have fabricated.