Review of biomimetic ordered microstructures in advancing synergistic integration of adhesion and microfluidics

Abstract

Many ordered arrangements are observable in the natural world, serving not only as pleasing aesthetics but also as functional improvements. These structured arrangements streamline cohesion while also facilitating the spontaneous drainage of liquids in microfluidics, resulting in effective separation and signal enhancement. Nevertheless, there is a substantial challenge when handling microstructured chips with microfluidic detection and adhesion. The arrangement of the adhesive interface's microstructure affects the liquid flow in the microfluidic chip, impacting the detection's sensitivity and accuracy. Additionally, the liquid in the microfluidic chip corrodes the adhesive material and structure, reducing the adhesion strength due to the hydration layer between the material and the contact interface. Therefore, this review explores the application of ordered structures in the integration of adhesion and microfluidics. We discussed the standard preparation method, appropriate materials, and the application of ordered structures in biomimetic adhesion and microfluidics. Furthermore, the paper discusses the major challenges in this field and provides opinions on its future developments.

Fig. 1. Schematic illustration of the types of ordered structures, biomimetic adhesion, and microfluidics.

Fig. 2. The material and fabrication method of bioinspired adhesion: (a) microscopic view of the bristles on the toe pads of a gecko; Reprinted with permission. Copyright 2000 Macmillan Magazines Ltd. (b) Polyimide microcolumns resembling gecko bristles. (c) Schematic of the preparation of the hierarchical hydrogel with an ordered micronano structure using polyethylene glycol diacrylate (PEGDA) and methacrylate gelatin (GelMA) as materials by a polydimethylsiloxane (PDMS) template; Reprinted with permission. Copyright 2021 Luyao Zhu et al. Exclusive Licensee Science and Technology Review Publishing House. (d) Schematic of the PDMS film constructed by an anodic aluminum oxide (AAO) template; Reprinted with permission. Copyright 2017 American Chemical Society. (e) Schematic of the fabrication of polyurethane (PU)-graphene/shape memory polymer (GSMP) by mold casting; Reprinted with permission. Copyright 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (f) Schematic of the preparation of T-shaped gradient micropillars (TG) with calcium carbonate nanoparticles (CaCO₃ NPs)/PDMS as materials by the PU mold method; Reprinted with permission. Copyright 2020 Wiley-VCH GmbH.

Fig. 3. Ordered microstructure of bioinspired adhesion. (a) Schematic of the elastic flat punch cylinder array; Reprinted with permission. Copyright 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (b) Schematic of soft elastomeric mushroom-like double re-entrant fibril arrays; Reprinted with permission. Copyright 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (c) Schematic of the ordered array of microneedles; Reprinted with permission. Copyright 2023 Elsevier Ltd. (d) Schematic of microneedle array with rear-facing barbs; Reprinted with permission. Copyright 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (e) Schematic of suction-cup-structured concave chambers combined with the MN structure; Reprinted with permission. Copyright 2020 Xiaoxuan Zhang et al. Exclusive Licensee Science and Technology Review Publishing House.

Fig. 4. Bioinspired adhesion of ordered structures: (a) a gecko bristle inspired array of microcolumns with T-shaped tips and a tree frog-inspired microcolumn with gradient modulus form TG to provide stronger adhesion and friction; Reprinted with permission. Copyright 2020 Wiley-VCH GmbH. (b) Gecko-inspired fibrous bristle array for inner surface adhesion of artificial periosteum; Reprinted with permission. Copyright 2021 Wiley-VCH GmbH. (c) Octopus suckers mimic patches with strong and reversible adhesion to both dry and wet surfaces; Reprinted with permission. Copyright 2021 Wiley-VCH GmbH. (d) Microneedles (MNs) have a mussel-like polydopamine (PDA) hydrogel and are surrounded by a ring of cavities that mimic the suckers of octopuses; Reprinted with permission. Copyright 2020 Xiaoxuan Zhang et al. Exclusive Licensee Science and Technology Review Publishing House.

Fig. 5. Microfluidic chips with ordered microstructures: (a) meta-structured membranes (MSMs) as substrates for fabricating integrated microfluidics and electronics; Reprinted with permission. Copyright 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (b) Microfluidic channels and electro circuits were first patterned on the ordered MN and then origami to form a double-side integrated chip; Reprinted with permission. Copyright 2020 Wiley-VCH GmbH. (c) Schematic diagram of hydrophobic surface based on bioinspired fabrication; Reprinted with permission. Copyright 2022 Wiley-VCH GmbH. (d) The photonic crystal pattern is assembled by elastic copolymer nanoparticles in an ordered microcolumn array to enable electronic skin biochemical detection; Reprinted with permission. Copyright 2022 Wiley-VCH GmbH. (e) Schematic diagram of constructing microfluidic channels in an ordered nanotentacle array; Reprinted with permission. Copyright 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fig. 6. Application of ordered bioinspired adhesion microfluidics: (a) intelligent origami silk fibroin microneedle-structured dressing (i-SMD) for biochemical sensing, motion monitoring and wound healing; Reprinted with permission. Copyright 2020 Wiley-VCH GmbH. (b) Bionic electronic skin attached to the skin for motion monitoring and biochemical detection; Reprinted with permission. Copyright 2022 Wiley-VCH GmbH. (c) The repastable microstructured fibroin adhesive (MSFA) strain sensor; Reprinted with permission. Copyright 2020 American Chemical Society. (d) Schematic diagram of a microfluidic chip for continuous sampling; Reprinted with permission. Copyright Springer Nature.