Colloidal motors are able to utilize fuels in their environment to swim at speeds of 10s of microns per second.  One of the original colloidal motors, a platinum-gold bimetallic rod, catalyzed the electrochemical degradation of H2O2 to produce an electric field that caused the particles to move.  The mechanism of movement is that during the reaction, electrons move through the metallic phase, while protons move through the solution phase, giving the electric field outside the particle.  In this talk, we describe how we have fabricated a trimer of Au-CdS-Ag, that acts similarly to the classic Pt-Au colloidal motors, except that now the motor is externally switchable.  Since the CdS is a semiconductor with a bandgap of 2.4 eV, in the absence of blue-green light, the electrons cannot pass through, and the motors do not move.  However, when blue light is applied (e.g., using a mercury arc lamp used for simple fluorescence microscopy), the CdS becomes conductive, allowing the electrons to pass, and allowing the motors to become mobile.  We describe the assembly methods used to fabricate the trimer motors, and we show the response in various levels of blue light.

Photoresponsive metal/cadmium sulfide colloidal micromotor assemblies

246th National Meeting (2013)

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