Multi-Fuel Driven Janus Micromotors

Here the first example of a chemically powered micromotor that harvests its energy from the reactions of three different fuels is presented. The new Al/Pd Janus microspheres—prepared by depositing a Pd layer on one side of Al microparticles—are propelled efficiently by the thrust of hydrogen bubbles generated from different reactions of Al in strong acidic and alkaline environments, and by an oxygen bubble thrust produced at their partial Pd coating in hydrogen peroxide media. High speeds and long lifetimes of 200 μm s^(−1) and 8 min are achieved in strong alkaline media and acidic media, respectively. The ability to autonomously adapt to the presence of a new fuel (surrounding environment), without compromising the propulsion behavior is illustrated. These data also represent the first example of a chemically powered micromotor that propels autonomously and efficiently in alkaline environments (pH > 11) without additional fuels. The ability to use multiple fuel sources to power the same micromotor offers a broader scope of operation and considerable promise for diverse applications of micromotors in different chemical environments

Multi-Fuel Driven Janus Micromotors

Here the first example of a chemically powered micromotor that harvests its energy from the reactions of three different fuels is presented. The new Al/Pd Janus microspheres—prepared by depositing a Pd layer on one side of Al microparticles—are propelled efficiently by the thrust of hydrogen bubbles generated from different reactions of Al in strong acidic and alkaline environments, and by an oxygen bubble thrust produced at their partial Pd coating in hydrogen peroxide media. High speeds and long lifetimes of 200 μm s^(−1) and 8 min are achieved in strong alkaline media and acidic media, respectively. The ability to autonomously adapt to the presence of a new fuel (surrounding environment), without compromising the propulsion behavior is illustrated. These data also represent the first example of a chemically powered micromotor that propels autonomously and efficiently in alkaline environments (pH > 11) without additional fuels. The ability to use multiple fuel sources to power the same micromotor offers a broader scope of operation and considerable promise for diverse applications of micromotors in different chemical environments

Artificial Enzyme-Powered Microfish for Water-Quality Testing

We present a novel micromotor-based strategy for water-quality testing based on changes in the propulsion behavior of artificial biocatalytic microswimmers in the presence of aquatic pollutants. The new micromotor toxicity testing concept mimics live-fish water testing and relies on the toxin-induced inhibition of the enzyme catalase, responsible for the biocatalytic bubble propulsion of tubular microengines. The locomotion and survival of the artificial microfish are thus impaired by exposure to a broad range of contaminants, that lead to distinct time-dependent irreversible losses in the catalase activity, and hence of the propulsion behavior. Such use of enzyme-powered biocompatible polymeric (PEDOT)/Au-catalase tubular microengine offers highly sensitive direct optical visualization of changes in the swimming behavior in the presence of common contaminants and hence to a direct real-time assessment of the water quality. Quantitative data on the adverse effects of the various toxins upon the swimming behavior of the enzyme-powered artificial swimmer are obtained by estimating common ecotoxicological parameters, including the EC_(50) (exposure concentration causing 50% attenuation of the microfish locomotion) and the swimmer survival time (lifetime expectancy). Such novel use of artificial microfish addresses major standardization and reproducibility problems as well as ethical concerns associated with live-fish toxicity assays and hence offers an attractive alternative to the common use of aquatic organisms for water-quality testing

Materials systems and autonomy in electromechanical sound art

Sound art is a difficult to categorise and broad genre description that draws together modes of creative practice which use sound as a medium or a subject. The field is considered to be critically underrepresented and under-theorised despite an increase of attention and popularity since the 1990s (Licht 2007, 2001, Cox 2009). This is partly as a consequence of an analytical and historical emphasis on textual and conceptual approaches which dominated the arts through the 1970s and 1980s (Cox 2011, 2013). In particular, acknowledgement of the influence of object-based and kinetic sculpture within the field of sound art is found to be inadequate (Chau 2014, Keylin 2015). This thesis presents an original body of sound art practice as a means through which to uncover and explore connections between sound art, experimental composition, kinetic art and sculpture. The term 'electromechanical' is used to identify this work, highlighting its particular concerns with the use of electrically animated or amplified materials. Through the production, exhibition, critical appraisal and contextualisation of the work new observations and distinctions within the field are presented. These include the identification of a 'closed system aesthetic' and the distinction between robotic and process driven approaches to electromechanical sound art. A further contribution to the field consists of a detailed consideration of sound art emerging from an intersection of experimental music and sculptural practices during the 1960s. The original works produced for the project, and their production are documented and described in detail alongside existing canonical and contemporary examples of sound art. Analysis of these works is informed by materialist and object-orientated critical positions, and science and technology studies. The method of art practice as research is described and extended in an original way that encompasses and applies a systems approach to creative practice

Acoustically propelled nanoshells.

Herein we report a new design for acoustic nanoswimmers, making use of a nanoshell geometry that was synthesized using a sphere template process. Such shell-shaped nanomotors display highly efficient acoustic propulsion on the nanoscale by converting energy from the ambient acoustic field into motion. The propulsion mechanism of the nanoshell motors relies on acoustic streaming stress over the asymmetric surface to produce the driving force for motion. The shell-shaped nanomotors offer a high surface area to volume ratio, allow for efficient scalability and provide higher cargo towing capacity (in comparison to acoustically propelled nanowires). Furthermore, a detailed study of the parameters relevant to propulsion performance, including the material density, size and shape of the motors, reveals that the nanoshell motors exhibit a different propulsion behavior from that predicted by recent theoretical and experimental models for acoustically propelled nanomotors. Such findings indicate that further studies are needed to predict the behavior of acoustic nanomotors with different geometry designs. Practical applications of the new nanoshell motors, including "on-the-move" capture and the transport of multiple cargoes and internalization and movement inside live MCF-7 cancer cells, are demonstrated. These capabilities hold considerable promise for designing fuel-free nanoswimmers capable of performing complex tasks for diverse biomedical applications

Acoustically propelled nanoshells.

Herein we report a new design for acoustic nanoswimmers, making use of a nanoshell geometry that was synthesized using a sphere template process. Such shell-shaped nanomotors display highly efficient acoustic propulsion on the nanoscale by converting energy from the ambient acoustic field into motion. The propulsion mechanism of the nanoshell motors relies on acoustic streaming stress over the asymmetric surface to produce the driving force for motion. The shell-shaped nanomotors offer a high surface area to volume ratio, allow for efficient scalability and provide higher cargo towing capacity (in comparison to acoustically propelled nanowires). Furthermore, a detailed study of the parameters relevant to propulsion performance, including the material density, size and shape of the motors, reveals that the nanoshell motors exhibit a different propulsion behavior from that predicted by recent theoretical and experimental models for acoustically propelled nanomotors. Such findings indicate that further studies are needed to predict the behavior of acoustic nanomotors with different geometry designs. Practical applications of the new nanoshell motors, including "on-the-move" capture and the transport of multiple cargoes and internalization and movement inside live MCF-7 cancer cells, are demonstrated. These capabilities hold considerable promise for designing fuel-free nanoswimmers capable of performing complex tasks for diverse biomedical applications

Reversible Swarming and Separation of Self-Propelled Chemically Powered Nanomotors under Acoustic Fields

The collective behavior of biological systems has inspired efforts toward the controlled assembly of synthetic nanomotors. Here we demonstrate the use of acoustic fields to induce reversible assembly of catalytic nanomotors, controlled swarm movement, and separation of different nanomotors. The swarming mechanism relies on the interaction between individual nanomotors and the acoustic field, which triggers rapid migration and assembly around the nearest pressure node. Such on-demand assembly of catalytic nanomotors is extremely fast and reversible. Controlled movement of the resulting swarm is illustrated by changing the frequency of the acoustic field. Efficient separation of different types of nanomotors, which assemble in distinct swarming regions, is illustrated. The ability of acoustic fields to regulate the collective behavior of catalytic nanomotors holds considerable promise for a wide range of practical applications

Ultrasound-Modulated Bubble Propulsion of Chemically Powered Microengines

The use of an ultrasound (US) field for rapid and reversible control of the movement of bubble-propelled chemically powered PEDOT/Ni/Pt micro­engines is demonstrated. Such operation reflects the US-induced disruption of normal bubble evolution and ejection, essential for efficient propulsion of catalytic microtubular engines. It offers precise speed control, with sharp increases and decreases of the speed at low and high US powers, respectively. A wide range of speeds can thus be generated by tuning the US power. Extremely fast changes in the motor speed (<0.1 s) and reproducible “On/Off” activations are observed, indicating distinct advantages compared to motion control methods based on other external stimuli. Such effective control of the propulsion of chemically powered micro­engines, including remarkable “braking” ability, holds considerable promise for diverse applications

Acoustic Microcannons: Toward Advanced Microballistics

Acoustically triggered microcannons, capable of loading and firing nanobullets (Nbs), are presented as powerful microballistic tools. Hollow conically shaped microcannon structures have been synthesized electrochemically and fully loaded with nanobullets made of silica or fluorescent microspheres, and perfluorocarbon emulsions, embedded in a gel matrix stabilizer. Application of a focused ultrasound pulse leads to the spontaneous vaporization of the perfluorocarbon emulsions within the microcannon and results in the rapid ejection of the nanobullets. Such Nbs “firing” at remarkably high speeds (on the magnitude of meters per second) has been modeled theoretically and demonstrated experimentally. Arrays of microcannons anchored in a template membrane were used to demonstrate the efficient Nbs loading and the high penetration capabilities of the ejected Nbs in a tissue phantom gel. This acoustic-microcannon approach could be translated into advanced microscale ballistic tools, capable of efficient loading and firing of multiple cargoes, and offer improved accessibility to target locations and enhanced tissue penetration properties

Functionalized Ultrasound-Propelled Magnetically Guided Nanomotors: Toward Practical Biomedical Applications

Magnetically guided ultrasound-powered nanowire motors, functionalized with bioreceptors and a drug-loaded polymeric segment, are described for “capture and transport” and drug-delivery processes. These high-performance fuel-free motors display advanced capabilities and functionalities, including magnetic guidance, coordinated aligned movement, cargo towing, capture and isolation of biological targets, drug delivery, and operation in real-life biological and environmental media. The template-prepared three-segment Au–Ni–Au nanowire motors are propelled acoustically by mechanical waves produced by a piezoelectric transducer. An embedded nickel segment facilitates a magnetically guided motion as well as transport of large “cargo” along predetermined trajectories. Substantial improvement in the speed and power is realized by the controlled concavity formation at the end of the motor nanowire using a sphere lithography protocol. Functionalization of the Au segments with lectin and antiprotein A antibody bioreceptors allows capture and transport of <i>E. coli</i> and <i>S. aureus</i> bacteria, respectively. Potential therapeutic applications are illustrated in connection to the addition of a pH-sensitive drug-loaded polymeric (PPy-PSS) segment. The attractive capabilities of these fuel-free acoustically driven functionalized Au–Ni–Au nanowires, along with the simple preparation procedure and minimal adverse effects of ultrasonic waves, make them highly attractive for diverse <i>in vivo</i> biomedical applications