Robust underwater
oil-repellent materials combining high
mechanical
strength and durability with superwettability and low oil adhesion
are needed to build oil-repellent devices able to work in water, to
manipulate droplet behavior, etc. However, combining all of these
properties within a single, durable material remains a challenge.
Herein, we fabricate a robust underwater oil-resistant material (Al2O3) with all of the above properties by gel casting.
The micro/nanoceramic particles distributed on the surface endow the
material with excellent underwater superoleophobicity (∼160°)
and low oil adhesion (<4 μN). In addition, the substrate
exhibits typical ceramic characteristics such as good antiacid/alkali
properties, high salt resistance, and high load tolerance. These excellent
properties make the material not only applicable to various liquid
environments but also resistant to the impact of particles and other
physical damage. More importantly, the substrate could still exhibit
underwater superoleophobicity after being worn under specific conditions,
as wear will create new surfaces with similar particle size distribution.
This approach is easily scalable for mass production, which could
open a pathway for the fabrication of practical underwater long-lasting
functional interfacial materials.
Additive manufacturing could open new opportunities in the design and fabrication of advanced composites and devices incorporating multiple phases. However, when it comes to the combination of inorganic materials (ceramics and metals) it is difficult to achieve the degree of structural control demanded by many advanced applications. To address this challenge, we have developed a means of embedded printing to build complex, fine structures within dense ceramics. We have formulated a self-healing ceramic gel that enables the movement of a printing nozzle in its interior and that heals without defect after it has passed. Upon subsequent heat treatment, the gel forms a dense, defect-free ceramic that encapsulates the printed structure. We demonstrate the potential of the technique through two case studies. One is the printing of light, sacrificial graphite structures to introduce complex microchannel arrangements in a ceramic for applications such a thermal management. The other is to embed dense steel framework structures in aluminum oxide to increase its fracture resistance. The approach enables the introduction of auxetic structures that generate works of fracture 50% greater than those obtained with simple fibre arrays and that are orders of magnitude above the fracture energy of the ceramic. These results suggest that embedded 3D printing can open the way to implement new designs in ceramic matrix composites.
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