Paper-based materials with precisely designed wettabilities show great potential for fluid transport control, separation, and sensing. To tune the wettability of paper, paper sheets are usually modified after the paper manufacturing process. This limits the complexity of the local wettability design. We combined the wettability design of the individual fibres with subsequent paper sheet fabrication through either fibre deposition or fibre printing. Using silica-based cellulose fibre functionalization, the wettability of the paper sheets, containing only one specific fibre type, could be gradually tuned from highly hydrophilic to highly hydrophobic, resulting in water exclusion. The development of a silica-functionalized fibre library containing mesoporous or dense silica coatings, as well as silica with varying precursor compositions, further enabled the variation of the paper wettability and fluid flow. By combining this fibre library with the paper fabrication process by (i) fibre deposition or (ii) fibre printing, the paper wettability architecture and thus the local fibre composition were adjusted without any further processing steps. This enabled the fabrication of papers with wettability integration, such as a wettability pattern or a Janus paper design, containing wettability gradients along the paper sheet cross section. This asymmetric wettability along all three spatial dimensions enabled side-selective oil–water separation.

中文翻译：

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多功能纸的单纤维涂层和增材制造

具有精确设计的润湿性的纸基材料在流体传输控制、分离和传感方面显示出巨大的潜力。为了调节纸张的润湿性，通常在纸张制造过程之后对纸张进行改性。这限制了局部润湿性设计的复杂性。我们通过纤维沉积或纤维印刷将单根纤维的润湿性设计与后续的纸张制造相结合。使用基于二氧化硅的纤维素纤维功能化，仅含有一种特定纤维类型的纸张的润湿性可以逐渐从高亲水性调整为高疏水性，从而实现防水。包含介孔或致密二氧化硅涂层以及具有不同前体成分的二氧化硅的二氧化硅功能化纤维库的开发进一步实现了纸张润湿性和流体流动的变化。通过（i）纤维沉积或（ii）纤维印刷将该纤维库与纸张制造工艺相结合，无需任何进一步的处理步骤即可调整纸张润湿性结构以及局部纤维成分。这使得能够制造具有润湿性集成的纸张，例如润湿性图案或Janus纸张设计，其中包含沿着纸张横截面的润湿性梯度。这种沿所有三个空间维度的不对称润湿性使得侧选择性油水分离成为可能。