In recent years, scientists have been inspired by desert beetles, lichens, and rice leaves to prepare various artificial patterns with anisotropic wetting properties, which have shown broad application prospects in the fields of cell culture, biosensing, and electronic manufactur

In recent years, scientists have been inspired by desert beetles, lichens and rice leaves to prepare various artificial patterns with anisotropic wetting properties, which have shown broad application in the fields of cell culture, biosensing and electronic manufacturing. Application prospects. However, the construction of precise patterns often requires precision technologies such as photolithography, plasma etching, and femtosecond laser . It involves the use of expensive consumables such as photoresist and molds/masks, which is not conducive to this from cost considerations. Extensive promotion of similar materials.

Recently, The team of Academician Wang Yuzhong and Professor Song Fei from the School of Chemistry of Sichuan University proposed an efficient maskless etching strategy. Combined with inkjet printing technology, it can quickly prepare precise complex patterns while achieving improved surface wettability. Differential regulation can be used to achieve information encryption and flexible electronic product manufacturing, and will bring broad prospects for the development of multifunctional materials.

Picture | Professor Sein Fei (source: data picture)

Recently, a related paper titled "A confined-etching strategy for intrinsic anisotropic surface wetting" patterning) was published on Nature Communications. Academician Wang Yuzhong and Professor Song Fei from the School of Chemistry of Sichuan University are the corresponding authors of , and doctoral student Feng Rui is the first author [1].

Figure | Related papers (Source: Nature Communications)

Figure | Dr. Feng Rui (Source: Data Figure)

It is reported that the team first used the breathing pattern method to prepare a triacetylcellulose film with a 3D honeycomb microporous structure. (honeycomb-like, HC for short). After immersing the HC film in a 5mol/L NaOH aqueous solution for 3 hours, the researchers found that the transparency of the film increased significantly, the surface pore structure was destroyed, and its surface hydrophilicity was significantly enhanced. In this regard, the team explained that this is because cellulose triacetate will be deacetylated and gradually degraded under the action of strong alkali, which leads to this phenomenon.

Interestingly, if ethanol is used to pre-wet the HC film surface, under the same conditions, it only takes half a minute to achieve the same etching effect mentioned above. In contrast, the micropore structure, opacity and water contact angle (WCA) of the HC membrane that was wetted by the NaOH aqueous solution for only half a minute did not change.

In response to this phenomenon, the team proposed a potential mechanism for the difference in etching rates in different solvents, that is, the porous structure will prevent the NaOH aqueous solution from infiltrating the pore cavity, while ethanol can quickly infiltrate the pore cavity and induce the NaOH aqueous solution to quickly infiltrate the pore cavity, thus Accelerate surface etching. Moreover, the researchers further demonstrated this mechanism by characterizing the fluorescence signal distribution of the micropore structure.

Since the surface can be controlled to achieve patterned etching by utilizing the above-mentioned etching rate difference, the team chose a more stable commercial ink instead of ethanol and drew patterns on the HC surface through an inkjet printer. According to reports, because the ink is hydrophilic, it can also induce the NaOH aqueous solution to quickly infiltrate the pore cavity and accelerate local etching, thereby achieving precise patterned etching.

Figure | Preparation strategy for precise patterns with anisotropic wettability (Source: Nature Communications)

Researchers said that based on ordinary inkjet printing technology, they were able to develop small dot array patterns with a resolution of 200 μm.

Picture | Inkjet printing auxiliary pattern (Source: Nature Communications)

Currently, stimulus-responsive information encryption materials have received more and more attention. The researchers said their results are applicable to such information storage and encryption scenarios.Specifically, this strategy happens to have a special etching time window. Within this window, it is possible to create hidden patterns that are highly stable in the air and visible after contact with liquid water. Such patterns are often difficult to pass through traditional etching methods. It is realized by patterning method; it is reported that the team successfully constructed a complex QR code pattern, which can not only appear quickly underwater, but also can be read accurately.

Figure | Information storage and encryption (Source: Nature Communications)

It is worth mentioning that this result can also be used to manufacture functional materials, such as flexible electronic products active in various fields such as displays, sensors, and medical devices. Ag (Argentum, silver) nanomaterials are often used to manufacture flexible electronic products due to their high conductivity and resistance to bending deformation. Using the wetting difference on the patterned surface, researchers can induce patterned self-spreading of the aqueous precursor solution and form a dense silver layer in situ, thereby preparing a flexible Ag electrode with high conductivity, which also provides a basis for self-patterning of functional materials. Assembly provides important ideas.

Overall, the patterned surface construction strategy proposed in this study is highly scalable and is expected to be further expanded to more material surfaces and bring more opportunities for their widespread promotion. Currently, this work has been authorized with Chinese invention patent ZL 202110570617.7.

-End-

Reference:
1.Feng, R., Song, F., Zhang, YD. et al. A confined-etching strategy for intrinsic anisotropic surface wetting patterning. Nat Commun 13, 3078 (2022). https:/ /doi.org/10.1038/s41467-022-30832-4