Light-controlled versatile manipulation of liquid metal droplets: a gateway to future liquid robots

Ren, Hongtai; Jin, Hu; Shu, Jiwu; Xie, Jie; Wang, Erlong; Ge, Du An; Tang, Shi‐Yang; Li, Xiangpeng; Li, Weihua

doi:10.1039/d1mh00647a

Cited by 33 publications

(33 citation statements)

References 46 publications

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“…Marangoni effect was induced by the local polarity change of the photoresponsive surfactant molecules, resulting in the movement of the oil droplets. [4] Tang et al used Marangoni effect to drive the liquid metal droplet in the surrounding liquid, which controlled the circuit [5] Here, we report an integrated droplet manipulation platform based on a photodeformable microfluidic chip, in which the transportation, fusion, and mixing of liquid slugs are controlled by the photo-induced Laplace pressure and the capillary condensation (Figure 1a-d). The Laplace pressure provides the driving force for the motion of the slugs, while the capillary condensation plays an important role in avoiding the "lock" of the fused slug in the microchannels, contributing to the integration of these liquid operations and the sequential control of reactions and detections in the same device.…”

Section: Introductionmentioning

confidence: 96%

“…Photo-induced manipulation of droplets is of considerably interest in microfluidics to perform the reactions and detections due to the remote and precise control of liquids in microscale. [1] The mechanisms of the previously reported photocontrolled droplet motion mainly focused on the Marangoni effect [2][3][4][5][6] or the wettability gradient. [7][8][9][10] For example, Faris et al dispersed water droplets in decanol and used laser to create temperature gradient, which generated the Marangoni effect to drive the droplets.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

Liu

Zhu

et al. 2021

Small Methods

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“…Such a droplet generator would pave the way to nano‐ and microdroplets for applications like actuators, [ 17,18 ] pumps, [ 19,20 ] tactile devices, [ 21 ] microswitches, [ 22,23 ] controllable structures, [ 24 ] and robots. [ 25,26 ] Galinstan droplets are typically stable owing to a nanometer‐thin oxide layer on the surface covering the liquid metal. While this oxide skin is useful in droplet formation, other applications like actuators and pumps call for the removal of this skin which can be ruptured chemically via acidic or basic solutions [ 27 ] as well as mechanically.…”

Section: Introductionmentioning

confidence: 99%

An On‐Chip Liquid Metal Plug Generator

et al. 2022

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Gallium‐based liquid metal nonspherical droplets (plugs) have seen increasing demand recently mainly because their high aspect ratios make them beneficial for a wide range of applications, including microelectromechanical systems (MEMS), microfluidics, sensor technology, radio‐frequency devices, actuators, and switches. However, reproducibility of the generation of such plugs, as well as precise control over their size, is yet challenging. In this work, a simple on‐chip liquid metal plug generator using a commercially available 3D microprinter is presented and the plug generator in poly(dimethylsiloxane) is replicated via soft lithography. Liquid metal plugs are generated via a combination of electrochemical oxidation, design of well‐defined constrictions based on Laplace pressure, and the application of modulated voltage control signals. It is shown that plugs of various aspect ratios can be generated reproducibly for channel widths of 0.5, 0.8, and 1.5 mm with constriction widths of 0.1 mm at 6 V. Laplace‐pressure‐controlled plugs in constricted channels are compared to modulated‐voltage‐generated plugs in straight channels showing that this technique provides significantly enhanced reproducibility and control over the size and spacing between the plugs. This work paves the way to sub‐millimeter liquid metal plugs generated directly on‐chip for on‐demand MEMS and microfluidic applications.

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“…15 The LM applications in flexible robots, 16,17 flexible electronics, 18,19 micromotors, 20,21 neural probes, 22 drug delivery, 23–25 chip cooling, 26 3D printing, 27–29 liquid metal pumps 30 and other fields 31–34 have attracted much attention. In addition, LM droplets can move under the action of ultrasound, 35 optical, 36,37 electrical, 38,39 magnetic, 40–42 and chemical mechanisms, 20 which makes LMs have great applications in microfluidics and robotics. 6,43 The controlled driving of LM droplets under the action of an electric field provides a new method to manufacture small vehicles.…”

Section: Introductionmentioning

confidence: 99%

Desktop-level small automatic guided vehicle driven by a liquid metal droplet

Ge¹,

Guo²,

Tao³

et al. 2022

Lab Chip

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Light-controlled versatile manipulation of liquid metal droplets: a gateway to future liquid robots

Abstract: The controlled actuation of liquid metal (LM) droplets has recently shown great potential in developing smart actuating systems for applications in robotics. However, there is a lack of a simple...

Cited by 33 publications

References 46 publications

An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

An Integrated Droplet Manipulation Platform with Photodeformable Microfluidic Channels

An On‐Chip Liquid Metal Plug Generator

Desktop-level small automatic guided vehicle driven by a liquid metal droplet

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