LED-based opto-wetting and fluidic transport for droplet mixing

Thomas, Tony; Unni, Harikrishnan Narayanan

doi:10.1007/s10404-019-2273-3

Cited by 11 publications

(5 citation statements)

References 39 publications

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“…(Figures S12,S13, Supporting Information). The moving speed of water reaches 0.34 mm s −1 , which satisfies the requirement for many biological applications with aqueous solutions such as the in‐vitro detection [ 26 ] and the cell sorting. [ 27 ]…”

Section: Resultsmentioning

confidence: 99%

An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

Liu

Zhu

et al. 2021

Small Methods

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Jiang et al. used the microstructure of the solid surface to make the droplet produce asymmetric wettability, which caused the droplet to flow spontaneously on the solid surface. [9] Ichimura et al. used the cis-trans isomerization of azophenyl groups to change the surface polarity, moving oil droplets by wettability gradient. [10] However, these droplet motions were limited to relative low speeds and simple linear trajectories, which were undesirable for the reactions and detections in an integrated platform (at least involving liquid transportation, fusion, separation, and mixing). [11,12] Recently, we presented a new way to manipulate droplets (liquid slugs) confined in a microtube by photo-induced asymmetric deformation. Photodeformable linear liquid crystal polymers (LLCPs) were chosen to fabricate the microtubes due to the excellent deformability and good processability for building 3D actuation structures. [13][14][15] Laplace pressure was generated when the microtubes deformed from cylinder-like to cone-like geometry attributed to the photoinduced orientation change of the liquid crystal units, [16][17][18][19] which led to the motion of the slug toward the narrower side. During the motion of the slug, mixing occurred simultaneously due to the formation of the vortex. [15] Furthermore, the fusion of two slugs was achieved in the junction of the Y-shaped tube. Although the slug transportation, mixing, and fusion have been realized individually in separated microtubes in the previous work, the integration of these operations in one platform has not been realized. The fused slug was "locked" in the junction, and was neither separated nor pro-The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.202100969.

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Section: Resultsmentioning

confidence: 99%

An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

Liu

Zhu

et al. 2021

Small Methods

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“…[21][22][23][24] Apart from such natural processes, droplet coalescence is relevant for many industrial applications as well, such as inkjet printing, 25 microfluidics, [26][27][28][29] and water treatment during crude oil and natural gas separation. 30,31 Further control of the process may involve the use of various additives, [32][33][34][35][36][37][38][39] such as surfactant, [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] which can reduce surface tension at fluid interfaces, crucial in multi-phase systems. For example, surfactant can stabilize droplets' surface or prevent their coalescence, thus improving the bio-compatibility in certain systems 59 or affecting the fusion, mixing, and manipulation of droplets in microfluidic devices.…”

Section: Introductionmentioning

confidence: 99%

Coalescence of surfactant-laden droplets

et al. 2023

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Droplet coalescence is an important process in nature and various technologies (e.g., inkjet printing). Here, we unveil the surfactant mass transport mechanism and report on several major differences in the coalescence of surfactant-laden droplets as compared to pure water droplets by means of molecular dynamics simulation of a coarse-grained model. Large-scale changes to bridge growth dynamics are identified, such as the lack of multiple thermally excited precursors, attenuated collective excitations after contact, slowing down in the inertial regime due to aggregate-induced rigidity and reduced water flow, and a slowing down in the coalescence rate (deceleration) when surfactant concentration increases, while at the same time, we also confirm the existence of an initial thermal, and a power-law, inertial, regime of the bridge growth dynamics in both the pure and the surfactant-laden droplets. Thus, we unveil the key mechanisms in one of the fundamental topological processes of liquid droplets containing surfactant, which is crucial in relevant technologies.

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“…However, it is extremely difficult to change once the liquid is in contact with the solid surface . For that reason, dynamic control of surface wettability with external stimuli such as electric fields in electrowetting experiments or light irradiation has gained considerable attention. − Applications where such control is highly desirable involve the modification of the liquid flow on surfaces (e.g., programmable − transport of a liquid or microfluidics , ), where tuning of drop formation, drop size, and drop size distribution is desired. In addition, photoswitchable thin organic films are interesting for optoelectronic devices. − …”

Section: Introductionmentioning

confidence: 99%

Molecular Kinetics and Wetting Dynamics of Self-Assembled Monolayers with Fluorinated Arylazopyrazoles

Golomb,

Arndt,

Honnigfort

et al. 2023

J. Phys. Chem. C

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Self-assembled monolayers (SAMs) with photoswitchable arylazopyrazole (AAP) silanes on SiO 2 surfaces that exhibit fluorinated terminal groups (CF 3 -AAP) were studied on a molecular level with time-dependent sum-frequency generation (SFG) spectroscopy as well as on a microscopic level with dynamic contact angle measurements. Through photoswitching of the CF 3 -AAP moieties in the SAM from their predominant E state to their predominant Z state, the molecules are driven from a linear to a bent configuration, which exposes the more hydrophilic azo group. This causes changes in surface wettability and a change in the static contact angle of about 10°. We analyzed the molecular kinetics of the photoswitching in the SAMs in detail by using both vibrational SFG and dynamic contact angle measurements. For this, we systematically changed the surface coverage of the AAP photoswitches by changing the deposition time of the fluorinated AAP. The molecular kinetics of the wetted monolayer are surprisingly slow, and the wetting dynamics are even slower when the SAM is closely packed, which we relate to a coupling between the molecular kinetics and the drop dynamics. In particular, it was found that the packing density of the SAMs and the possibility of incorporating water molecules in the SAM can have drastic influences on the wetting dynamics of CF 3 -AAP monolayers.

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LED-based opto-wetting and fluidic transport for droplet mixing

Cited by 11 publications

References 39 publications

An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

Coalescence of surfactant-laden droplets

Molecular Kinetics and Wetting Dynamics of Self-Assembled Monolayers with Fluorinated Arylazopyrazoles

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