Micro/nanopatterns can endow iontronic materials with unique properties such as wettability, adhesivity, mechanical adaptability, and environmental sensitivity, and contribute to improving the applied performance of iontronic sensors in real life. Traditional preparation methods of micro/nanopatterns mainly include top-down technologies such as photolithography and nanoimprinting, i.e., utilizing the force/light field provided by external equipment to construct microstructures on the surface of soft materials. Although complicated surface patterns can be precisely fabricated by top-down techniques, tedious steps, expensive equipment requirements, and limitations to dynamic regulation of the morphological structures and intrinsic components restrict its practicality and adaptability in developing multifunctional and multipurpose devices. On the contrary, various micro/nanopatterns on natural organisms’ surfaces resulted from self-organization, and also exhibited the advantages of simplicity, spontaneity, and dynamical adaptability, giving matrix unique properties such as self-cleaning, anti-reflection, as well as advanced and sophisticated tactile perception ability. How to draw inspiration from natural patterns and develop a simple and efficient general strategy for the fabrication of iontronic micropatterns with biomimetic features, and adapting to dynamic interactions in complex environments has always been one of the focuses of researchers.

To help with this problem, our group has been working on facile fabrication and dynamic regulation of hierarchical and multidimensional surface patterns, and also the interaction mechanism with multi-level environmental signals. We have pioneered the superior strategy for the fabrication of hierarchical and dynamic surface patterns through dynamic chemistry ^{1, 2}, and 2D ordered surface micro/nanopatterns by dynamic crosslink gradients ³ and ordered patterns with specific functions via growth strategy ^{4, 5}. Herein, according to our previous work, we present a robust method to create hierarchical and asymmetric iontronic micropatterns (denoted HAIMs) by incorporating localized photodimerization and asymmetric vapor oxidative polymerization supported by an in-situ phase separation process. Taking the spatiotemporal advantages of light, heat, and vapor, the morphology and electrical performance can be readily modulated as needed. With easy-to-process and programming-tunable features of surface morphology, ionic spatial distribution., and migration, these fascinating micropatterns can provide new insights into the development of patterned iontronic materials in a flexible, programmable, and functionally adaptive form.

Figure 1 Design, structure, and mechanism of Hierarchical and Asymmetric Iontronic Micropatterns. Schematic of the fabrication process for HAIMs through a-b) localized photodimerization, heating (to drive in-situ phase separation), and c) vapor oxidative polymerization. d-e) Optical images of the as-prepared HAIM, scale bar: 1 cm. f) The schematic of hierarchical and asymmetric Micropatterns upon HAIMs. g) SEM images of the resultant PEDOT in different areas corresponding to d-e, scale bar: 2 μm. h) Potential gradients changes of different samples within a limited time interval. i) Capacitance changes versus frequency for pristine iontronic host, IL-doped PEDOT @primary patterns, and resultant HAIM, respectively.

Based on the piezoionic effect within the resultant distinct doped PEDOT, HAIMs can serve as a scalable iontronic potential generator. The resultant HAIM exhibits the integrated properties of a highly polarizable poly (ionic liquid), ease of mobile ionic charge, capacitive and potentiometric gradient controllability, and long-term durability. The incorporation of photodimerization to fabricate HAIM was demonstrated to achieve promising bioelectronic modalities either on macro or micro scales.

For more details on our work, please see: https://www.nature.com/articles/s41467-022-34285-7

References

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2. Hou H, Yin J, Jiang X. Smart patterned surface with dynamic wrinkles. Acc. Chem. Res. 52, 1025-1035 (2019).
3. Hou H, et al. Reversible surface patterning by dynamic crosslink gradients: controlling buckling in 2D. Adv. Mater. 30, 1803463 (2018).
4. Li T, Hu K, Ma X, Zhang W, Yin J, Jiang X. Hierarchical 3D patterns with dynamic wrinkles produced by a photocontrolled diels–alder reaction on the surface. Adv. Mater. 32, 1906712 (2020).
5. Li T, et al. Micropatterns Fabricated by Photodimerization‐Induced Diffusion. Adv. Mater. 33, 2007699 (2021).