Combined Optical and Chemical Control of a Microsized Photofueled Janus Particle

Simoncelli, Sabrina; Summer, Johannes; Nedev, S.; Kühler, Paul; Feldmann, Jochen

doi:10.1002/smll.201503712

Cited by 26 publications

(48 citation statements)

References 28 publications

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“…Regarding specific-ion effects, our findings agree qualitatively with a recent experiment on gold-capped silica particles, showing a significant variation of the self-propulsion velocity with the used salts NaOH, NaCl, LiCl [9]. The data do not provide conclusive evidence for thermoelectric driving along the metal cap.…”

Section: Discussionsupporting

confidence: 78%

“…Since the thermophoretic self-propulsion is superposed on motion due to radiation pressure and gravity, these data do not provide an absolute measure of v s , but only qualitative differences upon changing the ions. In summary, the data of [9] confirm the existence of an electrolyte Seebeck effect for active > . The left panel shows the case of single grain.…”

Section: Comparison With Experimentssupporting

confidence: 60%

“…Laser-illuminated metal nanostructures provide versatile local heat engines [1], with optofluidic applications such as trapping of nanoobjects [2,3], manipulation of biological cells [4], microflows in capillaries [5], and colloidal assembly [6]. Similarly, thermally powered artificial microswimmers rely on the conversion of absorbed heat to motion; experimental realizations include metal-capped Janus particles that are driven by surface forces [7][8][9][10], and interface floaters that are advected by their self-generated Marangoni flow [11,12]. Force-free localization and steering have been achieved by temporal [13]or spatial [14] modulation of the laser power.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Nanoscale Seebeck effect at hot metal nanostructures

Majee

Würger

2018

New J. Phys.

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We theoretically study the electrolyte Seebeck effect in the vicinity of a heated metal nanostructure, such as the cap of an active Janus colloid in an electrolyte, or gold-coated interfaces in optofluidic devices. The thermocharge accumulated at the surface varies with the local temperature, thus modulating the diffuse part of the electric double layer. On a conducting surface with non-uniform temperature, the isopotential condition imposes a significant polarization charge within the metal. Surprisingly, this does not affect the slip velocity, which takes the same value on insulating and conducting surfaces. Our results for specific-ion effects agree qualitatively with recent observations for Janus colloids in different electrolyte solutions. Comparing the thermal, hydrodynamic, and ion diffusion time scales, we expect a rich transient behavior at the onset of thermally powered swimming, extending to microseconds after switching on the heating.T 2 µ , a parallel component along the particle surface; the latter exerts a force on the double layer and induces creep flow.

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Section: Discussionsupporting

confidence: 78%

Section: Comparison With Experimentssupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

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Nanoscale Seebeck effect at hot metal nanostructures

Majee

Würger

2018

New J. Phys.

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“…The decrease of velocity is owing to the increasing viscosity 33 . On the other hand, salts or proteins in close proximity to the AuNPs clusters could absorb thermal energy, resulting in lower velocity in complex media 47 . Note that the AuNPs-functionalized silica torpedo displays red fluorescence from AuNPs upon the irradiation of NIR laser owing to the surface plasmon resonance as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

A Light-Activated Explosive Micropropeller

Rao

et al. 2017

Sci Rep

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Self-propelled micro/nanomotors possess tremendous exciting promise in diverse fields. We describe an asymmetric, fuel-free and near-infrared light-powered torpedo micromotor, which is constructed by using a porous membrane-assisted layer-by-layer sol-gel method to form silica multilayer inside the pores, following by the deposition of gold nanoparticles on one end of the pores. In the absence of chemical fuels, the high propulsion of microtorpedoes under illumination of near-infrared light is owing to the photo-thermal effect of gold clusters, generating a thermal gradient inside the microtorpedoes. The speed of microtorpedoes is dependent on the laser powers and media. More interestingly, such fuel free-powered microtorpedoes could explode triggered by higher laser power at the predefined site and thus provide a new platform for future biomedical applications.

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“…It has been shown that, in addition to thermo-osmosis [11,12], the electrolyte Seebeck field [13][14][15][16][17][18] and concentration gradients of salt [16] or nonionic polymers [19,20], play an important role. These companion fields arise from specific solvation enthalpies of salt ions or nonionic solutes, and are at the origin of the "inverse" Soret effect, where the colloids accumulate in hot regions [16,19].…”

mentioning

confidence: 99%

Hydrodynamic interactions in DNA thermophoresis

Würger

2018

Soft Matter

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We theoretically study the molecular-weight dependence of DNA thermophoresis, which arises from mutual advection of the n repeat units of the molecular chain. As a main result we find that the dominant driving forces, i.e., the thermally induced permittivity gradient and the electrolyte Seebeck effect, result in characteristic hydrodynamic screening. In comparison with recent experimental data on single-stranded DNA (2 ≤ n ≤ 80), our theory provides a good description for the increase of the drift velocity up to n = 30; the slowing-down of longer molecules is well accounted for by a simple model for counterion condensation. It turns out that thermophoresis may change sign as a function of n: For an appropriate choice of the salt-specific Seebeck coefficient, short molecules move to the cold and long ones to the hot; this could be used for separating DNA by molecular weight. PACS numbers:When applying a temperature gradient on a colloidal dispersion, one observes thermally driven transport towards the hot or the cold [1,2]. In recent years, thermophoresis has been shown to provide a versatile means for manipulating DNA, including translocation through plasmonic nanopores [3], stretching in nanochannels [4,5], separation by molecular weight [6], sequencespecific detection with functionalized nanoparticles [7], and force-free trapping of single molecules [8]. Protein thermophoresis has become a standard technology in biomedical analysis [9], and the accumulation of RNA in hydrothermal pores is discussed as a scenario for biomolecular synthesis in the early evolution of life [10].In the last decade, much progress has been made concerning the physical mechanisms of thermophoresis of charged colloids. It has been shown that, in addition to thermo-osmosis [11,12], the electrolyte Seebeck field [13][14][15][16][17][18] and concentration gradients of salt [16] or nonionic polymers [19,20], play an important role. These companion fields arise from specific solvation enthalpies of salt ions or nonionic solutes, and are at the origin of the "inverse" Soret effect, where the colloids accumulate in hot regions [16,19]. Regarding the size dependence, there is conclusive evidence that the mobility of colloidal beads does not vary with the radius [21,22].In spite of the many experimental studies mentioned above, little is known on the molecular-weight dependence of DNA thermophoresis. If the hydrodynamic slowing-down of Brownian motion is well understood in terms of mutual advection of the repeat units [23], a more complex picture arises for phoretic motion where external forces are absent and which is driven by non-equilibrium surface properties. For short-ranged dispersion forces, hydrodynamic interactions are irrelevant and the thermophoretic velocity is constant [24,25]; deviations observed for very short polymers in organic solvents [26], arise probably from chemically different end groups. For DNA in a weak electrolyte, however, the electrostatic interaction length may attain tens of nanometers, which suggests an incomplet...

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Combined Optical and Chemical Control of a Microsized Photofueled Janus Particle

Cited by 26 publications

References 28 publications

Nanoscale Seebeck effect at hot metal nanostructures

Nanoscale Seebeck effect at hot metal nanostructures

A Light-Activated Explosive Micropropeller

Hydrodynamic interactions in DNA thermophoresis

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