Shape-Dependent Motion of Structured Photoactive Microswimmers

Nicholls, Dylan; DeVerse, Andrew; Esplin, Ra’Shae; Castañeda, John; Loyd, Yoseph; Nair, Raaman; Voinescu, Robert; Zhou, Chao; Wang, Wei; Gibbs, John G.

doi:10.1021/acsami.8b01940

Cited by 29 publications

(46 citation statements)

References 61 publications

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“…When activated, the single‐material microswimmers were propelled either toward or away from the oxide arms (see Videos S5 and S6 in the Supporting Information). We recently discovered the direction of motion is a function of such a particle's dimensions, and we discussed a possible propulsion mechanism for this system that we suspect is a combination of self‐phoresis and osmotic flow over the stationary surface over which the particles move . We note that the TiO 2 particles are highly impervious to degradation as expected for this material.…”

supporting

confidence: 65%

“…TiO 2 was evaporated as an oxide, and was subsequently annealed at 500 °C for 2 h to obtain primarily the more photoactive anatase phase, while Cu was converted to Cu 2 O after deposition by annealing in oxygen at 100 °C for 30 min: 4Cu + O 2 → 2Cu 2 O . To ensure uniformity between the structures, a close‐packed monolayer of monodisperse silica (SiO 2 ) microspheres (either 2 or 3 µm in diameter) served as nucleation centers for the depositing material, which ultimately formed elongated “arms” (see Figure a,b). In order to develop the TiO 2 /Cu 2 O hybrid microswimmers shown in Figure c, we initially deposited TiO 2 at an oblique angle onto spherical microparticles, identical to the process depicted in Figure a.…”

mentioning

confidence: 91%

“…We realized such a system by employing a dynamic fabrication method that enables developing particles with complex geometries from a wide range of materials and material combinations . We used this technique recently to investigate the dynamics of structured photoactive particles where a large portion of the structural underpinning consisted of a photocatalyst, titanium dioxide (TiO 2 ), and we found such particles exhibit motion that is sensitively shape‐dependent . Microswimmers made from photoactivated semiconductors have several advantages in comparison to those made from traditional metal catalysts like platinum, which include significantly lower cost, resistance to catalyst poisoning, the activity can be easily switched on‐and‐off, and the turnover rate is a function of both light intensity and wavelength.…”

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confidence: 99%

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Light‐Activated, Multi‐Semiconductor Hybrid Microswimmers

O'Neel-Judy

Nicholls

Castañeda

et al. 2018

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Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO ) and cuprous oxide (Cu O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light-activated microswimmers made from only TiO or Cu O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength-dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel-free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO /Cu O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light-activated particle, which is not limited to the specific geometries and materials presented in this study.

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confidence: 65%

mentioning

confidence: 91%

mentioning

confidence: 99%

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Light‐Activated, Multi‐Semiconductor Hybrid Microswimmers

O'Neel-Judy

Nicholls

Castañeda

et al. 2018

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“…It should be noted that in photocatalytic active colloidal matter, the particles are still autonomous, with motion being determined by thermal fluctuations that couple to the directed self‐propelled motion, despite the strength of propulsion being modifiable. The average motion is nevertheless strongly coupled to particle geometry, as we demonstrated in the recent past: the shape and size of the elongated photocatalytic segment of SiO 2 /TiO 2 microswimmers strongly affect speed and direction of motion . A schematic for the fabrication of similar microswimmers is shown in Figure a,b.…”

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confidence: 70%

“…Despite this lack of control, the average behavior of an ensemble of self‐propelled colloids can be tuned by targeted design of the particles themselves because shape dictates viscous drag and therefore mobility, while a combination of morphology and material properties determine the chemiosmotic flow, which gives rise to self‐propulsion. With these considerations, it becomes self‐evident that even autonomous motion can, on average, be engineered by fabricating microswimmers with appropriate geometries and chemical makeup.…”

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confidence: 99%

Engineering the Dynamics of Active Colloids by Targeted Design of Metal–Semiconductor Heterojunctions

Gibbs

Sarkar

Holterhoff

et al. 2019

Adv Materials Inter

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COMMUNICATION (1 of 7)Colloidal particles suspended in a fluid may become self-propelling when a catalyzed chemical reaction takes place at the interface between the particle and the fluid through which motion occurs. [1][2][3][4][5][6][7][8][9] If this reaction generates a local concentration gradient, [10] a chemiosmotic flow [11] over the particle's surface may arise. Such fluid flow is usually responsible for self-propulsion. This way of achieving active nano-and microscale autonomous motion is attractive since external fields, such as electric, [12] magnetic, [13][14][15][16][17][18] light, [19] or acoustic, [20,21] do not need to be applied, and moreover, nonequilibrium self-propelled systems

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2D‐Material‐Integrated Micromachines: Competing Propulsion Strategy and Enhanced Bacterial Disinfection

Huang

Guo

et al. 2022

Advanced Materials

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powered by chemical reactions encounters an arduous challenge, that is, the translocation speed is often compromised grievously in ionic suspension; [6] the alleviation of such an issue requires investigating new materials, schemes, and understanding of the complex mechanisms of locomotion. Furthermore, this far, the materials employed in chemical micro/ nanomotors that can operate continuously largely rely on noble metals such as Pt and Au combined with semiconductor oxides, for example, TiO 2 and ZnO, [1a,7] which are either expensive or are restricted in the UV region for light-powered chemical propulsion. It is highly desirable to explore new materials that can enhance the performance of chemical motors in an inexpensive, broadly applicable, and functional manner. [8] In the last decade, 2D materials, such as graphene, boron nitride, and transitionmetal-dichalcogenides have emerged as a promising class of materials owing to their 2D stacking atomic structures, high environmental stability, low cost, and the associated unique chemical and physical properties. [9] For instance, the 2D-structured molybdenum disulfide (MoS 2 ) possesses distinct semiconductor properties. The bandgap can be facilely tuned by its thickness from 1.2 eV (in bulk) to 1.8 eV (monolayer structure), accompanied by a transition from indirect to direct semiconductor bandgap structure, [10] which corresponds to an absorption edge of 1033.3 to 688.9 nm, mainly in the visible region. As a result, MoS 2 can respond to visible light with rapid optoelectric switching with a rise and decay time of 8 and 16 ms, respectively. [9a] Due to the 2D crystal structure, MoS 2 can be routinely made into van der Waals terminated thin films with lowdensity surface defects, ideal for flexible electronics. [11] Of paramount importance, when engineered with high-density defects, MoS 2 nanostructures demonstrate excellent chemical catalysis for hydrogen-evolution reduction, with a theoretical value close to that of Pt while at a much lower cost. [12] Furthermore, by leveraging the chemical properties of their defects, MoS 2 can readily react with mercury and be chemically functionalized for click-chemistry reactions. [9a] When applied in an aqueous medium, MoS 2 nanostructures are chemically stable even in an acid environment. [13] All these properties made the 2D MoS 2 a highly potential material that could make a remarkable impact on the field of micro/nanomachines, motors, and robots. For instance, MoS 2 was integrated into Pt nanotubes and demonstrated the controllable loading and release of doxorubicin. [14] 2D transition-metal-dichalcogenide materials, such as molybdenum disulfide (MoS 2 ) have received immense interest owing to their remarkable structureendowed electronic, catalytic, and mechanical properties for applications in optoelectronics, energy storage, and wearable devices. However, 2D materials have been rarely explored in the field of micro/nanomachines, motors, and robots. Here, MoS 2 with anatase TiO 2 is successfully integrated into an...

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Shape-Dependent Motion of Structured Photoactive Microswimmers

Cited by 29 publications

References 61 publications

Light‐Activated, Multi‐Semiconductor Hybrid Microswimmers

Light‐Activated, Multi‐Semiconductor Hybrid Microswimmers

Engineering the Dynamics of Active Colloids by Targeted Design of Metal–Semiconductor Heterojunctions

2D‐Material‐Integrated Micromachines: Competing Propulsion Strategy and Enhanced Bacterial Disinfection

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