Self-propelled Micromotors Research Articles

Motion-based, high-yielding, and fast separation of different charged organics in water.

We report a self-propelled Janus silica micromotor as a motion-based analytical method for achieving fast target separation of polyelectrolyte microcapsules, enriching different charged organics with low molecular weights in water. The self-propelled Janus silica micromotor catalytically decomposes a hydrogen peroxide fuel and moves along the direction of the catalyst face at a speed of 126.3 μm s(-1) . Biotin-functionalized Janus micromotors can specifically capture and rapidly transport streptavidin-modified polyelectrolyte multilayer capsules, which could effectively enrich and separate different charged organics in water. The interior of the polyelectrolyte multilayer microcapsules were filled with a strong charged polyelectrolyte, and thus a Donnan equilibrium is favorable between the inner solution within the capsules and the bulk solution to entrap oppositely charged organics in water. The integration of these self-propelled Janus silica micromotors and polyelectrolyte multilayer capsules into a lab-on-chip device that enables the separation and analysis of charged organics could be attractive for a diverse range of applications.

Hydrodynamics and propulsion mechanism of self-propelled catalytic micromotors: model and experiment.

The hydrodynamic behavior and propulsion mechanism of self-propelled micromotors are studied theoretically and experimentally. A hydrodynamic model to describe bubble growth and detachment is proposed to investigate the mechanism of a self-propelled conical tubular catalytic micromotor considering bubble geometric asymmetry and buoyancy force. The growth force caused by the growth of the bubble surface against the fluid is the driving force for micromotor motion. Also, the buoyancy force plays a primary role in bubble detachment. The effect of geometrical parameters on the micromotor velocity and drag force is presented. The bubble radius ratio is investigated for different micromotor radii to determine its hydrodynamic behavior during bubble ejection. The average micromotor velocity is found to be strongly dependent on the semi-cone angle, expelling frequency and bubble radius ratio. The semi-cone angle has a significant effect on the expelling frequency for conical tubular micromotors. The predicted results are compared to already existing experimental data for cylindrical micromotors (semi-cone angle δ = 0°) and conical micromotors. A good agreement is found between the theoretical calculation and experimental results. This model provides a profound explanation for the propulsion mechanism of a catalytic micromotor and can be used to optimize the micromotor design for its biomedical and environmental applications.

Fully Loaded Micromotors for Combinatorial Delivery and Autonomous Release of Cargoes

Integrating functional self-propelled Zinc micromotors are created by coup-ling electrodeposition with hard dual-templating synthesis. The micromotors concurrently possess four robust functions including a remarkably high loading capacity, combinatorial delivery of cargoes, autonomous release of encapsulated payloads, and self-destruction. This concept could be expanded to simultaneous encapsulation of various payloads for different functionalities such as therapy, diagnostics, and imaging.

Micromotor Enhanced Microarray Technology for Protein Detection

Microengines meet microarray technology. The transport of a target molecule toward a sensing surface can play a critical role in biodetection performance. The mixing induced by the motion of self-propelled micromotors can assist such transport and consequently enhance the performance of surface–based biosensing systems, particularly in microarray–based immunosensing that can be extended to DNA and cell analysis. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Biofunctionalized self-propelled micromotors as an alternative on-chip concentrating system.

Sample pre-concentration is crucial to achieve high sensitivity and low detection limits in lab-on-a-chip devices. Here, we present a system in which self-propelled catalytic micromotors are biofunctionalized and trapped acting as an alternative concentrating mechanism. This system requires no external energy source, which facilitates integration and miniaturization.

Trapping self-propelled micromotors with microfabricated chevron and heart-shaped chips

We demonstrate that catalytic micromotors can be trapped in microfluidic chips containing chevron and heart-shaped structures. Despite the challenge presented by the reduced size of the traps, microfluidic chips with different trapping geometries can be fabricated via replica moulding. We prove that these microfluidic chips can capture micromotors without the need for any external mechanism to control their motion.

Self-Propelled Micromotors for Cleaning Polluted Water

We describe the use of catalytically self-propelled microjets (dubbed micromotors) for degrading organic pollutants in water via the Fenton oxidation process. The tubular micromotors are composed of rolled-up functional nanomembranes consisting of Fe/Pt bilayers. The micromotors contain double functionality within their architecture, i.e., the inner Pt for the self-propulsion and the outer Fe for the in situ generation of ferrous ions boosting the remediation of contaminated water.The degradation of organic pollutants takes place in the presence of hydrogen peroxide, which acts as a reagent for the Fenton reaction and as main fuel to propel the micromotors. Factors influencing the efficiency of the Fenton oxidation process, including thickness of the Fe layer, pH, and concentration of hydrogen peroxide, are investigated. The ability of these catalytically self-propelled micromotors to improve intermixing in liquids results in the removal of organic pollutants ca. 12 times faster than when the Fenton oxidation process is carried out without catalytically active micromotors. The enhanced reaction–diffusion provided by micromotors has been theoretically modeled. The synergy between the internal and external functionalities of the micromotors, without the need of further functionalization, results into an enhanced degradation of nonbiodegradable and dangerous organic pollutants at small-scale environments and holds considerable promise for the remediation of contaminated water.

Micromotor‐Based High‐Yielding Fast Oxidative Detoxification of Chemical Threats

Oxidative decontamination: An effective strategy for the oxidative neutralization of organophosphorus nerve agents that is based on self-propelled micromotors has been developed. The movement of multiple motors across a peroxide-activated contaminated solution enhances the decontamination efficiency compared with common neutralization processes for chemical warfare agents.

Chemotactic Behavior of Catalytic Motors in Microfluidic Channels

Chemotactic Behavior of Catalytic Motors in Microfluidic Channels

Blood electrolytes exhibit a strong influence on the mobility of artificial catalytic microengines

The developments in biomedical sciences foresee the inclusion of self-propelled catalytic micromotors for in vivo therapeutic strategies in the near future. We show here that blood electrolytes, such as Na(+), K(+), Ca(2+), Cl(-), SO4(2-) and phosphates, decrease the mobility of the Pt catalyzed tubular microjets. This effect is significant and in many cases, the microjets are completely disabled at physiologically relevant concentrations of the ions. A strategy to counterbalance this negative influence is suggested. These findings have a strong influence in the field of bubble-propelled artificial micromotors, where applications in blood are often envisioned.

Collective behaviour of self-propelled catalytic micromotors

Biology widely employs catalytic reactions to power biomotors and cells. These dynamic entities can self-organize into swarms or self-assemble into functional micro- or nanostructures. Synthetic micro-/nanojet engines and nanomotors, driven by catalytic reactions, can move with high power and perform multiple tasks. Collective behavior of these microengines has recently been observed which includes swarming activities and the formation of multiconstituent entities. This feature article discusses recent developments, presents new discoveries on collective motion of self-propelled microjet engines and suggests next steps to undertake in the field of collective micromachines.

Magnetic and meniscus-effect control of catalytic rolled-up micromotors

Rolled-up catalytic micromotors with tubular structures are fabricated by rolling up strained Pt/Co/Ti metallic nanomembranes through selectively etching of the sacrificial lift off resist (LOR). The rolled-up micromotors present distinct motion behaviors in an organic/aqueous mixture fuel compared to those in a pure aqueous fuel. These self-propelled micromotors can move in pure aqueous fuel with a speed up to several millimeters per second. However, when placed into an organic/aqueous mixture fuel, the micromotors walk on the liquid surface. An intermediate Co layer facilitates a magnetically guided motion of these microtubular motors. The motion at the air–liquid interface can be regulated and suspended by the meniscus-climbing effect. Such meniscus-navigated motion represents a novel approach for regulation of micromotors at the air–liquid interface and opens the door to new and exciting operations of these micro-scale machines.