(349j) Award Submission: Highly Efficient Polymer-Based Microrockets and Their Biomedical Applications

The motion of synthetic micro/nano objects is of great fundamental and practical interest, and has thus stimulated major research efforts over the past decade in connection to diverse biomedical applications. Here we demonstrated a new polymer-based catalytic tubular microrocket synthesized using a template based electrodeposition method. The effects of different electropolymerized outer layers, including polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI) and of various inner metal surfaces (Ag, Pt, Au-catalase), upon the movement of such bilayer microtubes are evaluated and compared. These oxygen bubble propelled Pt based microrockets are only 8 μm long, can operate in very low levels of the hydrogen peroxide fuel (down to 0.2%) and achieve a consistently remarkable high speed of 1400 body lengths/s in physiological temperature (the speed record of all artificial nanomotors). These microrockets can also move efficiently in various fuel enhanced biological media such as human serum and can thus serve as an ideal platform for diverse biomedical and environmental applications. For example, lectin modified PANI/Pt microrockets are used for selective bacteria (E. Coli) isolation from food, clinical and environmental samples. Poly(3-aminophenylboronic acid) (PAPBA)/Ni/Pt microrockets coupling the selective monosaccharide recognition of the boronic-acid-based outer polymeric layer with the catalytic function of the inner platinum layer. The resulting boronic-acid based microrocket itself provides the ‘built in’ target recognition capability. 'On-the-fly' capture, transport and release of yeast cells (containing glucose on the cell wall) are illustrated. Molecularly imprinted polymers (MIPs) based microrockets can concentrates the fluorescent-tagged protein target onto the polymer outer layer without the need for additional external functionalization, allowing motion based extraction and isolation of Av-FITC from raw serum and saliva samples along with real-time visualization of the protein loading and transport. Besides the catalytic Pt based microrockets which rely on the hydrogen peroxide fuel, we also demonstrate a new hydrogen bubble propelled micromotor which can be driven by the natural environments (such as human stomach), without any additional chemical fuel. The tubular polyaniline/zinc microrockets display effective autonomous motion in extreme acidic environments (with a speed of over 100 body lengths per second). The ejection of hydrogen bubbles from the exposed zinc inner layer, upon its contact with acid, provides a powerful directional propulsion thrust. The observed speed-pH dependence holds promise for sensitive pH measurements in extreme acidic environments. The attractive guided cargo transport capabilities of these acid driven microrockets hold great promise for practical biomedical applications such as targeted drug delivery.