Catalytic Micromotors Research Articles

Asymmetric Pt/Au coated catalytic micromotors fabricated by dynamic shadowing growth

Asymmetric Pt/Au coated catalytic micromotors are fabricated by a dynamic shadowing growth method, and the exposed Au surface area A is changed systematically. The average moving speed u is found to follow the scaling relationship u∝A3/2, which agrees with the self-electrophoresis mechanism. Motion behaviors of micromotors with similar sizes and morphologies operating under a non-self-electrophoresis mechanism are compared with the Pt/Au micromotors, and in general, the self-electrophoresis mechanism gives higher activity for motors with similar sizes and morphologies.

Template-Assisted Fabrication of Salt-Independent Catalytic Tubular Microengines

A simplified template-assisted layering approach for preparing catalytic conical tube microjet engines based on sequential deposition of platinum and gold on an etched silver wire template followed by dicing and dissolution of the template is described. The method allows detailed control over the tube parameters and hence upon the performance of the microengine. The recoiling bubble propulsion mechanism of the tubular microengine, associated with the ejection of internally generated oxygen microbubbles, addresses the ionic-strength limitation of catalytic nanowire motors and leads to a salt-independent movement. Similar rates of bubble generation and motor speeds are observed in salt-free and salt-rich media (at elevated ionic-strength environments as high as 1 M NaCl). Plating of an intermediate nickel layer facilitates a magnetically guided motion as well as the pickup and transport of large (magnetic) "cargo". Surfactant addition is shown to decrease the surface tension and offer a more frequent formation of dense smaller bubbles. The new and improved motor capabilities along with the simple preparation route hold great promise for using catalytic micromotors in diverse and important applications.