Underwater Superaerophobicity Research Articles

Femtosecond laser induced underwater superaerophilic and superaerophobic PDMS sheets with through microholes for selective passage of air bubbles and further collection of underwater gas.

Controlling underwater bubble behavior on a solid surface is of great research significance, particularly in extreme cases. However, the realization of artificial underwater superaerophobic or superaerophilic surfaces is still a challenge. Herein, a micro/nanoscale hierarchical rough structure was formed on polydimethylsiloxane (PDMS) surface by one-step femtosecond laser ablation. The as-prepared surface showed superhydrophobicity in air and superaerophilicity in water. Interestingly, the wettability of such a PDMS surface could be easily switched to in-air superhydrophilicity and underwater superaerophobicity once it was further irradiated by oxygen plasma because the surface chemistry changed. The original femtosecond laser-structured underwater superaerophilic PDMS surface could absorb/capture bubbles, while the plasma-treated underwater superaerophobic surface had excellent anti-bubble ability in water. A rough through-microhole-array PDMS sheet was prepared by a mechanical drilling process and subsequent femtosecond laser ablation. The sheet could selectively allow bubbles to pass, that is, the porous underwater superaerophilic sheet allowed bubbles to pass through, while the porous underwater superaerophobic sheet was able to intercept bubbles in a water medium. Using the porous underwater superaerophilic PDMS sheet as the core component, a device that has great ability of collecting underwater bubbles/gas was also designed.

Bioinspired Design of Underwater Superaerophobic and Superaerophilic Surfaces by Femtosecond Laser Ablation for Anti- or Capturing Bubbles.

A micro-/nanoscale hierarchical rough structure inspired by the underwater superaerophobicity of fish scales was fabricated by ablation of a silicon surface by a femtosecond laser. The resultant silicon surface showed superhydrophilicity in air and became superaerophobic after immersion in water. Additionally, inspired by the underwater superaerophilicity of lotus leaves, we showed that the polydimethylsiloxane surface after femtosecond laser ablation exhibits superhydrophobicity in air and becomes superaerophilic in water. The underwater superaerophobic surface showed excellent antibubble ability, whereas the underwater superaerophilic surface could absorb and capture air bubbles in a water medium. The experimental results revealed that the in-air superhydrophilic surface generally shows superaerophobicity in water and that the in-air superhydrophobic surface generally shows underwater superaerophilicity. An underwater superaerophobic porous aluminum sheet with through microholes was prepared, and this sheet was able to intercept underwater bubbles and further remove bubbles from water. In contrast, the underwater superaerophilic porous polytetrafluoroethylene sheet could allow the bubbles to pass through the sheet. We believe that these results are highly significant for providing guidance to researchers and engineers for obtaining excellent control of bubbles' behavior on a solid surface in a water medium.

Remarkably simple achievement of superhydrophobicity, superhydrophilicity, underwater superoleophobicity, underwater superoleophilicity, underwater superaerophobicity, and underwater superaerophilicity on femtosecond laser ablated PDMS surfaces

Six different super-wettabilities were achieved on the same femtosecond laser ablated PDMS surface.

Self-cleaning superhydrophobic surfaces with underwater superaerophobicity

Nature-inspired engineering of roughness of the surfaces at micro and nano-length scales offers possibilities of tailoring materials for diverse applications including self-cleaning surfaces, droplet transportation, cell adhesion and oil-water separation. Recent efforts have begun to focus on employing femtosecond-long laser pulses to create such dual length scale roughness at the surface of different kinds of materials including metals, semiconductors and polymers. Herein, we report the fabrication of polymer surfaces that exhibit simultaneous superhydrophobicity and underwater superaerophobicity by replicating femtosecond laser fabricated patterns via soft lithography. Further, by tailoring a single parameter-the laser fluence-we demonstrate tunability of material parameters like anisotropy in wetting, contact angle hysteresis, work of adhesion, and droplet (air bubble) splitting (transport) of the replicated structures. We confirm, using micro-Raman spectroscopy and atomic force microscopy, that our laser patterning does not induce any chemical modification on the polymer but only induces physical modifications-changes in surface roughness-are responsible for the observed tailoring capability. We believe that the replication route provides a cost-effective and green approach to fabricate surfaces with superhydrophobicity and underwater superaerophobicity. Such surfaces can have enormous potential applications in microfluidic devices, droplet manipulation, and energy conversion and storage.