Bioinspired Functional Surfaces Enabled by Multiscale Stereolithography

Abstract

known as denticles that are thought to be multifunctional. It has been hypothesized that these surface features prevent biofouling and, more importantly, reduce fluid friction drag, which enables more efficient swimming. This has inspired the development of commercially successful products such as the Fastskin swimming suit by Speedo. Shark skin structures could also be applied to ships, underwater vehicles, airplanes, and pipelines to reduce energy waste from friction drag.Many studies have been conducted over the past few decades to understand the mechanism of drag reduction over shark skin-inspired surfaces. The physical causes responsible for drag reduction are reasonably well understood. [2][3][4] However, fabrication of such multifunctional surfaces remains a challenge. Although various methods have been used to reproduce shark skin geometry, a trade-off between throughput and resolution always exists and severely hinders the progress in this field. Some high-throughput methods include textured liners, [5,6] molding from real shark skin samples, [7] microcasting and wax printing, sampling from real shark skin, [8] and laser cutting. [9] However, these methods suffer from low resolution or difficulty in accurately reproducing the 3D geometry of shark skin, comprising dermal denticles attached to the surface. More importantly, given the vast design spaces involved, it is difficult to flexibly and quickly fabricate many different modified shapes and sizes that may be required in biomimetic studies. High-resolution digital fabrication methods such as two-photon lithography [10] have successfully fabricated highly detailed and accurate 3D shark skin denticles. [9] However, such fabrication processes can only produce samples with small areas. The small building extent, coupled with extremely low throughput, limits the value of such fabrication techniques for research purposes. As an emerging manufacturing technology, 3D printing has been playing an increasingly important role in various industries due to its advantages in high customization and fast prototyping, as well as the ability to fabricate complex shapes. [11][12][13][14][15][16][17] The flexibility of 3D printing also makes it very appealing for biomimetic studies. For example, 3D printing enables the development of artificial shark skin with textures of varying shape and size on arbitrary surface shapes. Indeed, some recent studies have successfully utilized 3D printing to fabricate shark skin structures. [9,18,19] Nevertheless, Additive manufacturing has many advantages in creating highly complex customized structures. In this study, a low-cost multiscale stereolithography technology that can print a macroscale object with microscale surface structures with high throughput is demonstrated. The developed multiscale stereolithography is realized by dynamic switching of laser spot size and adaptively sliced layer thickness. An optical filter based on subwavelength resonance grating is used to modify laser spot size for lasers with different wavelengths an...

Hybrid Laser Printing of 3D, Multiscale, Multimaterial Hydrogel Structures

“…Laser‐based methods that combine two separate additive processing steps or methods have been used to fabricate multiscale 3D structures . For instance, SLA was used to print multiscale surface features with a resolution of 37 µm by adaptively switching the laser spot and slice layer thicknesses .…”

“…Laser‐based methods that combine two separate additive processing steps or methods have been used to fabricate multiscale 3D structures . For instance, SLA was used to print multiscale surface features with a resolution of 37 µm by adaptively switching the laser spot and slice layer thicknesses . Shaped laser beams with adaptive layer thicknesses were used to print 3D multiscale structures with a resolution of 30 µm, although hollow microscale features were not reported .…”

Recent Progress in 3D Printing of Bioinspired Structures

“…(B) 3D printed friction anisotropic surfaces, inspired by the surface structures of the Filefish skin (Ji et al, 2018). Reproduced with the permission of 2018 Elsevier Ltd. (C) Low-cost multiscale stereolithography technology, used to print a macroscale object with microscale surface structures, inspired by shark skins and lotus leaf (Li et al, 2019b). Reproduced with the permission of 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

“…The anisotropy of the friction force of the different 3D printed engineering surfaces led to directional driving performance under external stretch or vibration, which has potential applications in directional actuation, intelligent sensors, and particular tribological systems. Li et al (2019b) developed a low-cost 3D printing technology (multiscale SLA) to print a macroscale object with microscale surface structures inspired by shark skin and lotus leaf, as shown in Figure 5C. The optical filter can modify laser spot size for lasers with different wavelengths to achieve a maximum resolution of 37 µm, which has the potential to serve as a powerful tool that can bring bioinspired structures into real-life applications.…”

Constructing a Dual-Function Surface by Microcasting and Nanospraying for Efficient Drag Reduction and Potential Antifouling Capabilities

“…Recently, different technologies that introduce bio-inspired functions have been investigated to create surfaces that exhibit excellent and synergistic performances similar to living organisms. Additive manufacturing was used to design microriblet features, and a 3D-printed shark skin demonstrated almost 10% average fluid drag reduction [17]. Lu used chemical deposition to fabricate a micro–nanohierarchical structure for superhydrophobicity and drag reduction.…”