Tailored 3D Mechanical Metamaterials Made by Dip‐in Direct‐Laser‐Writing Optical Lithography

Bückmann, Tiemo; Stenger, Nicolas; Kadic, Muamer; Kaschke, Johannes; Frölich, Andreas; Kennerknecht, Tobias; Eberl, C.; Thiel, Michael; Wegener, Martin

doi:10.1002/adma.201200584

Cited by 586 publications

(418 citation statements)

References 28 publications

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“…True antiplectic metachrony could be achieved by constructing the swimmer's body from an auxetic (negative Poisson's ratio) material. Passive, micro-scale auxetic metamaterials have been fabricated using technology that can be applied to LCEs 45,46 . Nevertheless, our microswimmers are capable of broader functionality than is found in nature, where any given species of ciliate exhibits only one mode of metachrony.…”

Section: Self-propulsion By Biomimetic Travelling-wave Body Deformationsmentioning

confidence: 99%

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

et al. 2016

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Microorganisms move in challenging environments by periodic changes in body shape. By contrast, current artificial microrobots cannot actively deform, exhibiting at best passive bending under external fields. Here, by taking advantage of the wireless, scalable and spatiotemporally selective capabilities that light allows, we show that soft microrobots consisting of photoactive liquid-crystal elastomers can be driven by structured monochromatic light to perform sophisticated biomimetic motions. We realized continuum yet selectively addressable artificial microswimmers that generate travelling-wave motions to self-propel without external forces or torques, as well as microrobots capable of versatile locomotion behaviours on demand. Both theoretical predictions and experimental results confirm that multiple gaits, mimicking either symplectic or antiplectic metachrony of ciliate protozoa, can be achieved with single microrobots. The principle of using structured light can be extended to other applications that require microscale actuation with sophisticated spatiotemporal coordination for advanced microrobotic technologies. 3Mobile micro-scale robots are envisioned to navigate within the human body to perform minimally invasive diagnostic or therapeutic tasks 1,2 . Biological microorganisms represent the natural inspiration for this vision. For instance, microorganisms successfully swim and move through a variety of fluids and tissues.Locomotion in this regime, where viscous forces dominate over inertia (low Reynolds number), is only possible through non-reciprocal motions demanding spatiotemporal coordination of multiple actuators 3 . A variety of biological propulsion mechanisms at different scales, from the peristalsis of annelids (Fig. 1a) to the metachrony of ciliates (Fig. 1b), are based on the common principle of travelling waves (Fig. 1c). These emerge from the distributed and self-coordinated action of many independent molecular motors 4,5 .Implementing travelling wave propulsion in an artificial device would require many discrete actuators, each individually addressed and powered in a coordinated fashion (Fig. 1d). The integration of actuators into microrobots that are mobile poses additional hurdles, since power and control need to be distributed without affecting the microrobots' mobility. Existing microscale actuators generally rely on applying external magnetic 6-10 , electric 11 , or optical 12,13 fields globally over the entire workspace. However, these approaches do not permit the spatial selectivity required to independently address individual actuators within a micro-device. Nevertheless, complex non-reciprocal motion patterns have been achieved by carefully engineering the response of different regions in a device to a spatially uniform external field 13,14 .The drawback is that this complicates the fabrication process, inhibits down-scaling and constrains the device to a single predefined behaviour. These challenges mean that most artificial microrobots actually have no actuators. Rather...

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Section: Self-propulsion By Biomimetic Travelling-wave Body Deformationsmentioning

confidence: 99%

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

et al. 2016

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“…Incorporating three-dimensional architecture into materials design across multiple length scales has led to the creation of advanced materials with novel mechanical properties, such as ultralight weight [1][2][3], negative Poisson's ratios [4,5], and near infinite bulk-to-shear modulus ratios [6,7]. The versatility of current fabrication methods and processing techniques engenders a virtually unbounded potential design space by which new materials can be created [8][9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Reexamining the mechanical property space of three-dimensional lattice architectures

et al. 2017

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Lightweight materials that are simultaneously strong and stiff are desirable for a range of applications from transportation to energy storage to defense. Micro-and nanolattices represent some of the lightest fabricated materials to date, but studies of their mechanical properties have produced inconsistent results that are not well captured by existing lattice models. We performed systematic nanomechanical experiments on four distinct geometries of solid polymer and hollow ceramic (Al 2 O 3 ) nanolattices. All samples tested had a nearly identical scaling of strength (ߪ ௬ ) and Young's modulus ‫)ܧ(‬ with relative density (ߩ̅ ), ranging from ߪ ௬ ∝ ߩ̅ ଵ.ସହ to ߩ̅ ଵ.ଽଶ and ‫ܧ‬ ∝ ߩ̅ ଵ.ସଵ to ߩ̅ ଵ.଼ଷ , revealing that changing topology alone does not necessarily have a significant impact on nanolattice mechanical properties. Finite element analysis was performed on solid and hollow lattices with structural parameters beyond those realized experimentally, enabling the identification of transition regimes where solid-beam lattices diverge from existing analytical theories and revealing the complex parameter space of hollow-beam lattices. We propose a simplified analytical model for solid-beam lattices that provides insight into the mechanisms behind their observed stiffness, and we investigate different hollow-beam lattice parameters that give rise to their aberrant properties. These experimental, computational and theoretical results uncover how architecture can be used to access unique lattice mechanical property spaces while demonstrating the practical limits of existing beam-based models in characterizing their behavior.

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“…Ablation via laser is a direct subtractive method for patterning substrates 27 . (2) Additive patterning is an approach that involves building up pillars, ridges, and 3D structures, often by exposing resists that are crosslinked upon exposure and wet development (that is, rinsing the noncrosslinked resist) [28][29][30][31] . (3) Finally, moulding techniques can be used to transform a pattern, for example, to mould high ridges from deep trenches and vice versa [32][33][34][35] .…”

Section: High-aspect-ratio Microstructures (Harms)mentioning

confidence: 99%

High-aspect-ratio nanoimprint process chains

et al. 2017

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Different methods capable of developing complex structures and building elements with high-aspect-ratio nanostructures combined with microstructures, which are of interest in nanophotonics, are presented. As originals for subsequent replication steps, two families of masters were developed: (i) 3.2 μm deep, 180 nm wide trenches were fabricated by silicon cryo-etching and (ii) 9.8 μm high, 350 nm wide ridges were fabricated using 2-photon polymerization direct laser writing. Both emerging technologies enable the vertical smooth sidewalls needed for a successful imprint into thin layers of polymers with aspect ratios exceeding 15. Nanoridges with high aspect ratios of up to 28 and no residual layer were produced in Ormocers using the micromoulding into capillaries (MIMIC) process with subsequent ultraviolet-curing. This work presents and balances the different fabrication routes and the subsequent generation of working tools from masters with inverted tones and the combination of hard and soft materials. This provides these techniques with a proof of concept for their compatibility with high volume manufacturing of complex micro-and nanostructures.Keywords: cryo-etching; direct 6 write laser lithography; high aspect ratio; moulding; nanoimprint lithography; Ormocer; photonic nanofences; 2-photon polymerization INTRODUCTION High-aspect-ratio microstructures (HARMS), that is, structures with a large height/width ratio, have found many applications 1,2 such as X-ray gratings 3 , gas chromatography columns 4 , magnetic coils 5 , X-ray telescopes 6 , micro-gears 7 , micro-capacitors with highaspect-ratio (HAR) cantilevers 8 , and micromechanical and microoptical elements 9,10 . These structures exhibit aspect ratios (ARs) of over 10 and almost vertical sidewalls, making them much more challenging to develop than the structures typically used in planar technology with moderate ARs of 1 to 2. They are therefore characterized by an intermediate state between two-and threedimensional (2D and 3D), that is, a 2D planar design that is extended into the vertical dimension and often called . There are several methods to produce HAR structures on typical planar substrates, most of them relying on the anisotropy of subtractive pattern transfer of a low AR masking layer into an underlying resist or substrate, that is, by using mask based ultraviolet (UV)-photolithography (PL) with an AR up to 5, silicon etching (for example, dry etching) with an AR up to 20, and direct write laser lithography (DWL) and X-ray lithography with ARs 420 (Refs. 12-15). These methods are continually being improved to produce a higher AR and smaller lateral dimensions. Furthermore, they are enlarged by new techniques that are often subsets of etching processes with different advantages and disadvantages. One of those challenges is the suitability for submicron and nanopatterning, that is, structures with lateral sizes much smaller than 1 μm and the possibility to combine micro-with nanostructures in the same material.There are three main approaches: (1)...

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Tailored 3D Mechanical Metamaterials Made by Dip‐in Direct‐Laser‐Writing Optical Lithography

Cited by 586 publications

References 28 publications

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

Reexamining the mechanical property space of three-dimensional lattice architectures

High-aspect-ratio nanoimprint process chains

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