This review describes recent developments in self-propelling nano- and micro-scale swimming devices. The ability of these devices to transport nano-scale components a fluidic environment is demonstrated. Furthermore, the adaptations needed for meet biological challenges such as targeted drug delivery are highlighted. Particular emphasis placed on describing autonomously powered driven by asymmetrical chemical reactions. Methods control speed direction using external fields described,...

Abstract The advent of autonomous self-propulsion has instigated research towards making colloidal machines that can deliver mechanical work in the form transport, and other functions such as sensing cleaning. While much progress been made last 10 years on various mechanisms to generate self-propulsion, ability steer self-propelled devices so far more limited. A critical barrier increasing impact motors is directing their motion against Brownian rotation, which randomizes particle...

The propulsion velocity of active colloids that asymmetrically catalyze a chemical reaction is probed experimentally as function their sizes. It found over the accessible range, decays size, with rate compatible an inverse size dependence. A diffusion-reaction model for concentrations fuel and waste molecules takes into account two-step process asymmetric catalytic activity on surface colloid shown to predict similar behavior at large limit, saturation smaller

The effect of added salt on the propulsion Janus platinum-polystyrene colloids in hydrogen peroxide solution is studied experimentally. It found that micromolar quantities potassium and silver nitrate salts reduce swimming velocity by similar amounts, while leading to significantly different effects overall rate catalytic breakdown peroxide. argued seemingly paradoxical experimental observations could be theoretically explained using a generalised reaction scheme involves charged...

Active colloids are small scale materials capable of producing enhanced motion within fluid environments. The field active has grown rapidly over the last ten years and is approaching maturity where viable applications reach. In this review, recent advances surveyed with a strong emphasis on developments that can enable autonomous applications, execute useful tasks without external interventions. These likely to prove transformative as resulting technologies will be significantly less...

Nonconductive Janus particle swimmers made by coating fluorescent polymer beads with hemispheres of platinum have been fully characterized using video microscopy to reveal that they undergo propulsion in hydrogen peroxide fuel away from the catalytic patch. The shadows fluorescence signal half each swimmer allow orientation be observed directly and correlated quantitatively resulting swimming direction. direction is consistent both bubble release diffusiophoretic mechanisms.

In this paper we show that processes such as Brownian motion, convection, sedimentation, and bacterial contamination can cause small particles to move through liquids in a fashion which may be mistaken nanopropulsion. It is shown particle tracking subsequent statistical analysis essential ascertain if actually propel themselves, or they are propelled by another process. Specifically find it necessary calculate the mean-squared displacement of at both short long time intervals, direction...

A class of artificial microswimmers with combined translational and rotational self-propulsion is studied experimentally. The chemically fueled are made doublets Janus colloidal beads catalytic patches that positioned at a fixed angle relative to one another. mean-square displacement the angular active analyzed in context simple Langevin description, using which physical characteristics such as spontaneous velocities extracted. Our work suggests strategies for designing could follow...

In this work, we show that the asymmetrical distribution of mass at surface catalytic Janus swimmers results in devices preferentially propelling themselves upward a gravitational field. We demonstrate existence gravitaxis phenomenon by observing trajectories fueled swimmers, which generate thrust along vector pointing away from their metallically coated half. report as size spherical swimmer increases, propulsive are no longer isotropic with respect to gravity, and they start pronounced...

The hydrodynamic flow field around a catalytically active colloid is probed using particle tracking velocimetry both in the freely swimming state and when kept stationary with an external force. Our measurements provide information about fluid velocity vicinity of surface colloid, confirm mechanism for propulsion that was proposed recently. In addition to offering unified understanding nonequilibrium interfacial transport processes at stake, our results open way thorough description...

Model poly(glycerol monomethacrylate)-based macromonomers have been used to prepare sterically stabilized polystyrene latexes by either aqueous emulsion or alcoholic dispersion polymerization, affording mean latex diameters of approximately 107 1188 nm respectively as judged dynamic light scattering. Such PGMA50−PS appropriate surface wettability stabilize 25−250 μm oil-in-water Pickering emulsions, depending on the concentration and oil type. Colloidosomes were formed covalent cross-linking...

Spin coating polymer blend thin films provides a method to produce multiphase functional layers of high uniformity covering large surface areas. Applications for such include photovoltaics and light-emitting diodes where performance relies upon the nanoscale phase separation morphology spun film. Furthermore, at micrometer scales, route self-organized structures templating applications. Understanding factors that determine final phase-separated in these systems is consequently an important...

Inkjet-printed enzyme-powered silk-based micro-rockets are able to undergo autonomous motion in a vast variety of fluidic environments including complex media such as human serum. By means digital inkjet printing it is possible alter the catalyst distribution simply and generate varying trajectory behavior these micro-rockets. Made silk scaffolds containing enzymes highly biocompatible non-biofouling. Production small-scale devices that can autonomously thrust via catalytic reactions within...

Catalytic Janus colloids produce rapid motion in fluids by decomposing dissolved fuel. There is great potential to exploit these "autonomous chemical swimmers" applications currently performed diffusion limited passive colloids. Key application areas for include transporting active ingredients drug delivery, gathering analytes medical diagnostics, and self-assembling into regular structures used photonic materials lithographic templating. For delivery controlling colloidal key order target...

Inkjet bioprinting is a new and versatile technology which has found novel applications in cell biology associated biomedical research. Cells suspended low-viscosity liquid medium can be readily dispensed using piezoelectric thermal actuation-based drop-on-demand inkjet printers, are the most commonly used printing technologies. As advantage of producing high resolution precision prints, it one suitable technologies for bottom-up deposition building intricate biological constructs. In...

The ability to control the degree of spin, or rotational velocity, for catalytic swimming devices opens up potential access well defined spiralling trajectories, enhance cargo binding rate, and realise theoretically proposed behaviour such as chiral diffusion. Here we assess impart a well-defined spin individual Janus swimmers by using glancing angle metal evaporation onto colloidal crystal break symmetry patch due shadowing neighbouring colloids. Using this approach demonstrate relationship...

The field of active colloids is attracting significant interest to both enable applications and allow investigations new collective colloidal phenomena. One convenient system that has been much studied spherical Janus particles, where a hemispherical coating platinum decomposes hydrogen peroxide produce rapid motion. However, at present producing these relies on physical vapor deposition (PVD) process, which difficult scale requires access expensive equipment. In this work, it demonstrated...

Through the technique of stroboscopic microscopy we are able to directly identify a number different mechanisms by which colloids self-assemble during spin-coating.

Translationally diffusive behavior arising from the combination of orientational diffusion and powered motion at microscopic scales is a known phenomenon, but peculiarities evolution expected position conditioned on initial orientation have been neglected. A theory given spiral mean trajectory depending upon propulsion speed, angular velocity, diffusion, rate random chirality reversal. We demonstrate experimental accessibility this effect using both tadpole-like Janus sphere dimer rotating...

Spherical colloids decorated with a surface coating of catalytically active material are capable producing autonomous motion in fluids by decomposing dissolved fuel molecules to generate gaseous product, resulting momentum generation bubble growth and release. Such attractive as they relatively simple manufacture compared more complex tubular devices have the potential be used for applications such environmental remediation. However, despite this interest, little effort has been devoted...

Abstract Stirring small volumes of solution can reduce immunoassay readout time, homogenize cell cultures, and increase enzyme reactivity in bioreactors. However, at present many scale stirring methods require external actuation, which be cumbersome. To address this, here, reactive inkjet printing is shown to able produce autonomously rotating biocompatible silk‐based microstirrers that enhance fluid mixing. Rotary motion generated either by release a surface active agent (small molecular...