Oscillatory Light‐Emitting Biopolymer Based Janus Microswimmers

María‐Hormigos, Roberto; Escarpa, Alberto; Goudeau, Bertrand; Ravaine, Valérie; Perro, Adeline; Kuhn, Alexander

doi:10.1002/admi.201902094

Cited by 13 publications

(24 citation statements)

References 63 publications

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“…The colloidal waves reported here exhibit autonomous, periodic, and local flows that mesoscopically transport colloidal objects that are chemically coupled and is therefore noticeably different from other systems that may appear superficially similar. First, even though there have been reports of chemically propelled microswimmers with oscillating speeds, enabled by the periodic coalescence, growth, and release of large O 2 bubbles ( 51 ), by incorporating BZ reactions in droplets ( 52 ) or by periodic changes in the buoyancy during the decomposition of hydrogen peroxide ( 53 ), none generates colloidal waves likely because they lack an appropriate coupling mechanism in the population.…”

Section: Discussionmentioning

confidence: 99%

Unraveling the physiochemical nature of colloidal motion waves among silver colloids

Chen

Zhou

et al. 2022

Sci. Adv.

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Traveling waves are common in biological and synthetic systems, including the recent discovery that silver (Ag) colloids form traveling motion waves in H 2 O 2 and under light. Here, we show that this colloidal motion wave is a heterogeneous excitable system. The Ag colloids generate traveling chemical waves via reaction-diffusion, and either self-propel through self-diffusiophoresis (“ballistic waves”) or are advected by diffusio-osmotic flows from gradients of neutral molecules (“swarming waves”). Key results include the experimental observation of traveling waves of OH − with pH-sensitive fluorescent dyes and a Rogers-McCulloch model that qualitatively and quantitatively reproduces the key features of colloidal waves. These results are a step forward in elucidating the Ag-H 2 O 2 -light oscillatory system at individual and collective levels. In addition, they pave the way for using colloidal waves either as a platform for studying nonlinear phenomena, or as a tool for colloidal transport and for information transmission in microrobot ensembles.

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Section: Discussionmentioning

confidence: 99%

Unraveling the physiochemical nature of colloidal motion waves among silver colloids

Chen

Zhou

et al. 2022

Sci. Adv.

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“…[21,22] "Two-faced" Janus microrobots, consisting of a photocatalytic semiconductor asymmetrically covered by a metal layer, represent the most efficient light-powered microrobots. [23][24][25][26] These microrobots can move via the self-electrophoretic mechanism due to the asymmetric generation of charges under light irradiation, establishing a local electric field that induces their motion. [27] The metal layer plays a crucial role as it improves the charge separation at the semiconductor/metal interface, enhancing the microrobots' speed and photocatalytic properties.…”

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confidence: 99%

Photo‐Fenton Degradation of Nitroaromatic Explosives by Light‐Powered Hematite Microrobots: When Higher Speed Is Not What We Go For

2021

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past decades, tremendous efforts have been made toward the precise control of microrobots' motion mechanism, speed, and directionality, with the aim to accomplish specific tasks in complex environments. [9][10][11] The self-propulsion of these tiny machines can be induced by chemical fuels (H 2 O 2 , glucose, urea) or external stimuli such as light, magnetic fields, and ultrasound. [12][13][14][15][16][17][18][19][20] Light is a very attractive energy source to power microrobots because it is powerful, renewable, and abundant. Consequently, light-driven microrobots have recently attracted great attention and have been reported moving at the cellular level, overcoming the major limitation of toxic fuels such as H 2 O 2 , or degrading "on-the-fly" harmful pollutants in water. [21,22] "Two-faced" Janus microrobots, consisting of a photocatalytic semiconductor asymmetrically covered by a metal layer, represent the most efficient light-powered microrobots. [23][24][25][26] These microrobots can move via the self-electrophoretic mechanism due to the asymmetric generation of charges under light irradiation, establishing a local electric field that induces their motion. [27] The metal layer plays a crucial role as it improves the charge separation at the semiconductor/metal interface, enhancing the microrobots' speed and photocatalytic properties. [9] Different metals, especially noble metals like Au and Pt, have been combined with different photocatalysts (UV-lightactivated TiO 2 and ZnO, visible light-activated Fe 2 O 3 and BiOI)Self-powered micromachines are considered a ground-breaking technology for environmental remediation. Light-powered Janus microrobots based on photocatalytic semiconductors asymmetrically covered with metals have recently received great interest as they can exploit light to move and contemporarily degrade pollutants in water. Although various metals have been explored and compared to design Janus microrobots, the influence of the metal layer thickness on motion behavior and photocatalytic properties of microrobots have not been investigated yet. Here, light-driven hematite/Pt Janus microrobots are reported and fabricated by depositing Pt layers with different thickness on hematite microspheres produced by hydrothermal synthesis. It has been demonstrated that the thicker the metal layer the higher the microrobots speed. However, when employed for the degradation of nitroaromatic explosives pollutants through the photo-Fenton mechanism, higher rate of H 2 O 2 consumption leads to higher propulsion speed of microrobots and lower pollutants degradation efficiencies owing to less H 2 O 2 involved in the photo-Fenton reaction. This work presents new insights into the motion behavior of light-powered Janus micromotors and demonstrates that high speed is not what really matters for water purification via photo-Fenton reaction, which is important for the future environmental applications of micromachines.The ORCID identification number(s) for the author(s) of this article can be found under

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“…Recently, two different self‐propelled chemiluminescent swimmers have been developed. In the first example, Prussian Blue‐filled alginate hydrogel beads exhibit dynamic oscillatory behavior coupled with light emission [105] . For this, the symmetry of the Prussian Blue beads had to be broken, transforming them into Janus particles, via a pH gradient generated by water electrolysis in an electrochemical cell.…”

Section: (Electro)chemiluminescent Dynamic Systemsmentioning

confidence: 99%

Electrochemistry‐Based Light‐Emitting Mobile Systems

et al. 2020

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Light‐emitting mobile systems are presented as an important concept for direct visualization and tracking of active objects. Motion or light emission can be achieved by different electrochemical mechanisms. Various devices, that generate light by fluorescence, (electro)chemiluminescence or via light emitting diodes are shown to be an interesting alternative for the detection or release of target molecules, providing straightforward optical imaging. This review summarizes and discusses the recent advances with respect to the design and the potential applications of such original systems.

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Oscillatory Light‐Emitting Biopolymer Based Janus Microswimmers

Cited by 13 publications

References 63 publications

Unraveling the physiochemical nature of colloidal motion waves among silver colloids

Unraveling the physiochemical nature of colloidal motion waves among silver colloids

Photo‐Fenton Degradation of Nitroaromatic Explosives by Light‐Powered Hematite Microrobots: When Higher Speed Is Not What We Go For

Electrochemistry‐Based Light‐Emitting Mobile Systems

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