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.

Unidirectional underwater gas bubble (UGB) transport on a surface is realized by buoyant force or wettability gradient force (F wet-grad ) derived from a tailored geography. Unfortunately, intentional control of the UGB over transport speed, direction, and routes on horizontal planar surfaces is rarely explored. Herein reported is a light-responsive slippery lubricantinfused porous surface (SLIPS) composed of selective lubricants and super-hydrophobic micropillar-arrayed Fe 3 O 4 /polydimethylsiloxane film. Upon this SLIPS, the UGB can be horizontally actuated along arbitrary directions by remotely loading/discharging unilateral near-infrared (NIR) stimuli. The underlying mechanism is that F wet-grad can be generated within 1 s in the presence of a NIR-trigger due to the photothermal effect of Fe 3 O 4 . Once the NIR-stimuli are discharged, F wet-grad vanishes to break the UGB on the SLIPS. Moreover, performed are systematic para meter studies to investigate the influence of bubble volume, lubricant rheology, and F wet-grad on the UGB steering performance. Fundamental physics renders the achievement of antibuoyancy manipulation of the UGBs on an inclined SLIPS. Significantly, steering UGBs by horizontal SLIPS to configurate diverse patterns, as well as facilitating light-control-light optical shutter, is deployed. Compared with the previous slippery surfaces, light-responsive SLIPS is more competent for manipulating UGBs with controllable transport speed, direction, and routes independent of buoyancy or geography derivative force.

Marangoni-effect-driven actuators (MDAs) have the advantages of direct light-to-work conversion and convenient operation, which makes it widely researched in the cutting-edge fields including robots, micromachines, and intelligent systems. However, the MDA relies on the surface tension difference and it only works on the 2D liquid-air interface. Besides, the MDAs are normally pure black due to the light-absorption material limitation. Herein, a transparent light-driven 3D movable actuator (LTMA) and a 3D manipulation strategy are proposed. The LTMA is composed of photothermal nanoparticles-doped temperature-responsive hydrogel, whose surface energy changes as the nanoparticles absorb light energy. The 3D manipulation strategy combines Marangoni effect with photothermal buoyancy flow for realizing complex self-propellant and floating/sinking motions. The LTMA can perform more advanced tasks such as 3D obstacle avoidance and 3D sampling. Benefiting from the porous structure of hydrogel, LTMA can naturally absorb the chemical molecules for remote sampling and automated drug delivery. The light-driven, transparent, three-dimensionally movable, and programmable actuator has promising prospects in the field of micromachines and intelligent systems.

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.