Harnessing Photochemical Shrinkage in Direct Laser Writing for Shape Morphing of Polymer Sheets

Bauhofer, Anton; Krödel, Sebastian; Ryś, Jan; Bilal, Osama R.; Constantinescu, Andréï; Daraio, Chiara

doi:10.1002/adma.201703024

Cited by 74 publications

(59 citation statements)

References 36 publications

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“…Therefore, lithography is quite limited when considering applications where a large surface area with sub‐micron or nanoscale topology is needed, as it is not suited for scale‐up. Recently, some researchers have demonstrated how polymerization‐induced shrinkage and polymerization stress can be exploited to drive the formation of surface features . The work of Guo et al.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, some researchers have demonstrated how polymerization-induced shrinkage and polymerization stress can be exploited to drive the formation of surface features. [12][13][14][15] The work of Guo et al employed a post-polymerization approach to create topographical features which resulted from stress-instability in thin films of polymer brushes. [14] With this methodology, polymer brushes were selectively cross-linked near the brush/air interface by post-modification in poor solvents, resulting in surfaces with wrinkle morphology.…”

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confidence: 99%

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Rapid, Template‐Less Patterning of Polymeric Interfaces for Controlled Wettability via in Situ Heterogeneous Photopolymerizations

Szczepanski

Darmanin

Godeau

et al. 2018

Macro Chemistry & Physics

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Tuning macroscopic behavior between a synthetic surface and the surrounding environment requires precise engineering of micro‐ and nanoscale features at the interface. As one example, the geometry and spacing of topographical structures can be manipulated to modify interfacial interactions with water. If optimized correctly, topographical features can impart macroscopic wetting behavior that goes well beyond what is expected from the chemistry of the surface materials, such as strong hydrophobicity from intrinsically hydrophilic materials. However, developed techniques such as templating or nano‐lithography require significant processing times and are often ill‐suited for in situ applications. This work shows that polymeric interfaces with regular, ordered topographical features can be generated using a rapid in situ photopolymerization technique that requires no templating nor additional processing to generate or manipulate surface features. Maximizing the local differential in polymerization‐induced shrinkage between heterogeneous domains results in the formation of robust 3D surface features. Furthermore, the spacing and density of these features can be optimized through the phase separation process, yielding surfaces with variable wetting (θw ≈ 90–130°). These results demonstrate that template‐ and mask‐less surface patterning is possible with rapid polymerization techniques and that it can be easily manipulated to vary surface wetting behavior.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Rapid, Template‐Less Patterning of Polymeric Interfaces for Controlled Wettability via in Situ Heterogeneous Photopolymerizations

Szczepanski

Darmanin

Godeau

et al. 2018

Macro Chemistry & Physics

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show abstract

“…μm, n=6) or the hemisphere part of the cones (173 ± 7 μm, n=6) is very reproducible but slightly smaller than the designed 200 μm diameter. The shrinkage is due to the residual stresses when covalent bonds are formed, [20] and could be predicted and compensated for in the future. [21] After pyrolysis, the geometries of sphere and cone are the same, but the size shrunk about 3 fold (Figure 2b and 2d), with an average diameter of spheres of 65 ± 4 μm (n=5) and the hemisphere part of the cones of 65 ± 5 μm (n=4).…”

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confidence: 99%

3D‐Printed Carbon Electrodes for Neurotransmitter Detection

et al. 2018

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Implantable neural microsensors have significantly advanced neuroscience research, but the geometry of most probes is limited by the fabrication methods. Therefore, new methods are needed for batch-manufacturing with high reproducibility. Herein, a novel method is developed using two-photon nanolithography followed by pyrolysis for fabrication of free-standing microelectrodes with a carbon electroactive surface. 3D-printed spherical and conical electrodes were characterized with slow scan cyclic voltammetry (CV). With fast-scan CV, the electrodes showed low dopamine LODs of 11±1 nm (sphere) and 10±2 nm (cone), high sensitivity to multiple neurochemicals, and high reproducibility. Spherical microelectrodes were used to detect dopamine in a brain slice and in vivo, demonstrating they are robust enough for tissue implantation. This work is the first demonstration of 3D-printing of free-standing carbon electrodes; and the method is promising for batch fabrication of customized, implantable neural sensors.

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“…As soon as the voxel writes a second interconnected layer, a rapid unsteady deformation of the first written filament is observed (Figure S2, Supporting Information). This deformation is induced by photochemical shrinkage that unfolds local residual stresses as a response to external stimuli . The ongoing laser writing process is stabilizing the initial deformation leaving behind only small imperfections at the tip of the microtube (Figure , second row, t = 5 s).…”

Section: Resultsmentioning

confidence: 99%

Two‐Photon Vertical‐Flow Lithography for Microtube Synthesis

Lölsberg

Cinar

Felder

et al. 2019

Small

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with high throughput. [21][22][23] By interrupting the fluid flow during the exposure through an interference phase mask, the stop-flow lithography technique enables high-resolution fabrication of patterned particles. [24][25][26] In combination with digital mirror devices, the vertical-flow lithography (VFL) method can synthesize anisotropic particles in real time using a light source that is aligned with the fluid flow. [27,28] To overcome the limiting resolution of these projection techniques, scanning two-photon lithography is coupled with CFL for the synthesis of truly 3D particles and fibers. [29,30] The current two-photon CFL (TP-CFL) methods offer fast in-plane laser writing speeds surpassing 1 mm s −1 using scanning galvanometer mirrors; however, the out-of-plane writing speed is still limited by the piezo-driven nanostage movement of typically 100 µm s −1 . [31] The transfer of the continuous real-time synthesis from particles (0D), fibers (1D), and planar geometries (2D) toward microtubes (3D) represents an intricate challenge with respect to the synthesis of i) high aspect ratio microtubes with ii) rigorous control over the morphology and surface topology by coupling scanning two-photon lithography with a vertical flow to obtain iii) high in-plane and out-of-plane synthesis speeds with iv) sub-micrometer resolution. Below, for the first time, we demonstrate two-photon VFL (TP-VFL) that combines the advantages of TP-CFL with VFL to control the out-of-plane fabrication speed by the vertical flow inside a microfluidic channel. This unique approach is an enabling step toward the synthesis of tubular scaffolds for vascular tissue engineering, microstents for intravascular pressure reduction, microneedles for transdermal drug delivery, nerve guides for neuronal regeneration, and porous hollow fiber membranes for separation applications. [32][33][34][35][36] Results and Discussion Fluid Flow-Coupled Two-Photon PolymerizationTo validate the proposed hypothesis, we design and fabricate a microfluidic chip featuring precise fluid-flow control (Figure 1). The designed master mold (Figure 1a) is printed onto a glass slide using maskless dip-in laser lithography (Figure 1b). [37,38] Soft-lithography replica molding is used to obtain the silicone microfluidic chip plasma bonded to a glass slide (Figure 1c). [39] Two-photon vertical-flow lithography is demonstrated for synthesis of complex-shaped polymeric microtubes with a high aspect ratio (>100:1). This unique microfluidic approach provides rigorous control over the morphology and surface topology to generate thin-walled (<1 µm) microtubes with a tunable diameter (1-400 µm) and pore size (1-20 µm). The interplay between fluid-flow control and two-photon lithography presents a generic high-resolution method that will substantially contribute toward the future development of biocompatible scaffolds, stents, needles, nerve guides, membranes, and beyond. Lithography

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Harnessing Photochemical Shrinkage in Direct Laser Writing for Shape Morphing of Polymer Sheets

Abstract: International audienc

Cited by 74 publications

References 36 publications

Rapid, Template‐Less Patterning of Polymeric Interfaces for Controlled Wettability via in Situ Heterogeneous Photopolymerizations

Rapid, Template‐Less Patterning of Polymeric Interfaces for Controlled Wettability via in Situ Heterogeneous Photopolymerizations

3D‐Printed Carbon Electrodes for Neurotransmitter Detection

Two‐Photon Vertical‐Flow Lithography for Microtube Synthesis

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