Manipulation of gas bubbles in an aqueous ambient environment is fundamental to both academic research and industrial settings. Present bubble manipulation strategies mainly rely on buoyancy or Laplace gradient forces arising from the sophisticated terrain of substrates. However, these strategies suffer from limited manipulation flexibility such as slow horizontal motion and unidirectional transport. In this paper, a high performance manipulation strategy for gas bubbles is proposed by utilizing ferrofluid-infused laser-ablated microstructured surfaces (FLAMS). A typical gas bubble (<2 μL) can be accelerated at >150 mm/s2 and reach an ultrafast velocity over 25 mm/s on horizontal FLAMS. In addition, diverse powerful manipulation capabilities are demonstrated including antibuoyancy motion, “freestyle writing”, bubble programmable coalescence, three-dimensional (3-D) controllable motion and high towing capacity of steering macroscopic object (>500 own mass) on the air–water interface. This strategy shows terrain compatibility, programmable design, and fast response, which will find potential applications in water treatment, electrochemistry, and so on.
Manipulating gas bubbles in aqueous ambient is of great importance for applications in water treatment, gas collection, and matter transport. Here, a kind of Janus foam is designed and fabricated by one-step ultrafast laser ablation of one side of the copper film, which is treated to be superhydrophobic. Janus foam exhibits not only the capability of unidirectional transport of underwater bubbles but also gas collection with favorable efficiency up to ∼15 mL cm −2 min −1 . The underlying physical mechanism is attributed to the cooperation of the buoyancy, adhesion, and wetting gradient forces imposed on the bubbles. As a paradigm, the underwater chemical reaction between the unidirectional CO 2 gas flow and the alkaline phenolphthalein solution is demonstrated via Janus foam. This facile and low-cost fabrication approach for Janus foam will find broad potential applications in effective bubble transport, carbon capture, and controllable chemical reactions under aqueous conditions.
Superhydrophobic/superhydrophilic surfaces (SBS/SLS) with excellent water repellency/adhesion are important in both academic research and industrial settings owing to their intriguing functions in tiny droplet and gas bubble manipulation. However, most manipulation strategies involving SBS/SLS are limited to their large-area fabrication or sophisticated morphology designs, which distinctly hinders their practical uses. In this paper, we design and fabricate superhydrophobic polydimethylsiloxane narrowing dual rails (SNDRs) beneath a superhydrophilic stainless steel sheet by one-step femtosecond laser ablation. Our SNDR tracks are capable of transporting gas bubbles in various volumes from wide end to narrow end spontaneously and unidirectionally underwater, even when they are bent. The mechanical analysis for diverse geometrical dual-rail configurations in bubble transportation performance is further discussed. Finally, we experimentally demonstrate the intriguing capability of lossless mixing of gas bubbles at a designed volume ratio on a multiple SNDR combination. This approach is facile and flexible, and will find broad potential applications such as intelligent bubble transport, mixing, and controllable chemical reactions in interfacial science and microfluidics.
High‐performance droplet transport is crucial for diverse applications including biomedical detection, chemical micro‐reaction, and droplet microfluidics. Despite extensive progress, traditional passive and active strategies are restricted to limited liquid types, small droplet volume ranges, and poor biocompatibilities. Moreover, more challenges occur for biological fluids due to large viscosity and low surface tension. Here, a vibration‐actuated omni‐droplets rectifier (VAODR) consisting of slippery ratchet arrays fabricated by femtosecond laser and vibration platforms is reported. Through the relative competition between the asymmetric adhesive resistance originating from the lubricant meniscus on the VAODR and the periodic inertial driving force originating from isotropic vibration, the fast (up to ≈60 mm s−1), programmable, and robust transport of droplets is achieved for a large volume range (0.05–2000 µL, Vmax/Vmin ≈ 40 000) and in various transport modes including transport of liquid slugs in tubes, programmable and sequential transport, and bidirectional transport. This VAODR is general to a high diversity of biological and medical fluids, and thus can be used for biomedical detection including ABO blood‐group tests and anticancer drugs screening. These strategies provide a complementary and promising platform for maneuvering omni‐droplets that are fundamental to biomedical applications and other high‐throughput omni‐droplet operation fields.
Manipulating underwater bubbles (UGBs) is realized on morphology-tailored or stimuli-responsive slippery lubricant-impregnated porous surface (SLIPS). Unfortunately, the volatile lubricants (e. g., silicone oil, ferrofluid) greatly decrease their using longevity. Designed is light-responsive paraffin-infused Fe3O4-doped slippery surface (LR-PISS) by incorporation of hybrid lubricants and superhydrophobic micropillar-arrayed elastometric membranes resulted from one-step femtosecond laser vertically scanning. Upon LR-PISS, the dynamic motion control bwteen pinning and sliding along free routes over UGB could be realized by alternately loading/discharging NIR-trigger. The underlying principle is that when the NIR was applied, UGB would be actuated to slide along the NIR trace because the irradiated domain melts for a slippery surface within 1.0 s. Once the NIR is removed, the liquefied paraffin would be reconfigured to solid phase for pinning a moving UGB within 0.5 s. Newly explored hydrokinetics imparts us with capability of steering UGBs to arrange any desirable patterns and switch light-path behaving as the light-control-light optical shutter. In comparison with previously reported SLIPS, current LR-PISS unfolds unparalleled ultrarobust antidisturbance ability even in flowing liquid ambient. More significantly, even subjected to physical damage, underwater LR-PISS is capable of in situ self-healing within 13 s under the assistance of remote NIR. The results here could inspire the design of robust bubble manipulator and further boost their applications in optofluidics and all-optical modulators.
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