Ultrasound Control And Propel Micro/Nanomachines

Synthetic micro-/nanomachines,which are able to mimic the amazing natural system,can convert energy sourse into movement,and are expected to help humanity complete environmental and biological tasks.Ultrasound,with major advantages of on-demand motion control,long lifetime,and great biocompatibility,have been one of the great potential toward in vivo drug delivery and clinical diagnosis.In this dissertation,the use of ultrasound to control and propel micro/nanomachines including stopping tubular microengine,reversible swaming behavior of nanowires,microrail-assised assemble nanowires and magneto-acoustic hybrid propulsion are demonstrated.1.Rapid and reversible control the movement of bubble-propelled microengines.Ultrasound interrupted normal bubble evolution from PEDOT/Ni/Pt microengines,and resulted in stopping the microengines.Extremely fast changes in motor speed and reproducible "On/Off" activations are observed,and a wide range of speeds can thus be generated by adjusting the ultrasound power,indicating distinct advantages compared to motion control methods based on other external stimuli.2.Reversible swarming and separation of self-propelled chemically powered nanomotors under acoustic fields.The use of acoustic fields to induce reversible assembly of catalytic nanomotors,controlled swarm movement,and separation of different nanomotors were demonstrated.The swarming mechanism relies on the interaction between the acoustic field and individual nanomotors,which resulted in rapidly assembly around the nearest pressure node.The ability of acoustic fields to regulate the collective behavior of catalytic nanomotors has great potencial in enrichment detection and target drug delivery.3.Microrail-assisted acoustic-powered reversible assemblies of nanowires were demonstrated.The microrails embedded into the ultrasound field can make surrounding acoustic potential non-uniform distribution,and cause nanowires to assemble along the mcirorails.The width of the microrail can determine the dynamic assembly of nanowires in parallel to or in perpendicular to the direction of the microrail,which is also validated by numerical simulations.Such microrail-assisted capabilities of assembling and transporting nanowires provide great potential in photonic crystals,cell collection and nanoelectronic fabrication.4.Magneto-acoustic hybrid nanomotor,displays efficient propulsion in the presence of acoustic or magnetic fields.The hybrid nanomotors comprised a concave end(ultrasound)and a helical structure(magnetic),are synthesized though template-assisted electrochemical deposition and segment-selective chemical etching.These hybrid nanomotors powered by ultrasound could propeled in seawater,cell culture medium,serum and blood,and exhibit a biomimetic collective behavior by alternating the actuating magnetic and acoustic fields.Such adaptive hybrid operation and controlled collective behavior hold considerable promise for designing smart nanovehicles.