Patterning of Soft Matter across Multiple Length Scales

Abstract

2609wileyonlinelibrary.com at the moment. [ 2,7,8 ] While the order within an assembly (nanometer scale) is extremely high, when dispersed, most supramolecular materials form macroscopically isotropic assemblies. Moreover, spatial control at device dimensions is challenging. Examples where such control is highly benefi cial or even crucial for device performance are in optoelectronic devices [8][9][10] and in tissue engineering, where a macroscopically organized polymer scaffold is necessary for the growth of highly aligned tissue, such as muscle fi bers and neural tissue. [11][12][13][14] So far, different strategies toward macroscopic alignment of polymeric and supramolecular materials have been developed, including photolithography, [ 15,16 ] soft lithography, [ 3,16 ] electrospinning, [17][18][19] electric [20][21][22][23] and magnetic [ 24,25 ] fi eld alignment, as well as shear fl ow alignment. [ 9,11 ] These techniques all have demonstrated their benefi ts, but also strong limitations such as incompatibility with (aqueous) soft matter, low susceptibilities, and/or poor spatial control across multiple length scales.In this manuscript, we use liquid crystal (LC) templating with patternable substrates to obtain full spatial control in our self-assembled materials. This approach has numerous advantages: (i) it does not depend on specifi c interactions between the assembly and the template and thus it can be applied to a wide range of materials; (ii) any desired (hierarchical) structure can be imprinted on the substrate and reproduced in the assembly; (iii) the desired product can be (chemically) modifi ed after organization (in our case to generate optically active π-conjugated polymers); and (iv) the template can be removed which only leaves the functional material on the substrate. In nonaqueous solvents (bulk thermotropic liquid crystals), the concept of LC templating was demonstrated successfully [ 10,[26][27][28][29][30][31] but in aqueous solutions unidirectional alignment at large length scales is rarely realized, let alone locally controlled. [ 32 ] The limited success in water is related to the amphiphilic lyotropic LCs that are notoriously diffi cult to align on commonly used substrates such as rubbed polyimide. [ 33,34 ] In addition, these lyotropic LCs are incompatible with electric fi elds (because of dielectric and Joule heating as well electrochemical degradation), and they can interfere with the desired self-assembly process of a supramolecular material. [ 35 ] To overcome these disadvantages, we use a template of a lyotropic chromonic LC (LCLC) which is a rigid plank-like molecule Controlling the organization of functional supramolecular materials at both short and long length scales as well as creating hierarchical patterns is essential for many biological and electrooptical applications. It remains however an extremely challenging objective to date, particularly in water-based systems. In this work, it is demonstrated that water-processable self-assembling materials can be organized from mic...

Fully Stable and Homogeneous Lyotropic Liquid Crystal Alignment on Anisotropic Surfaces

“…Despite its aromatic structure, it is optically transparent in the visible range. DSCG has been applied as a biosensor, an optical compensator for LCDs, and as an LC template for several functional materials, even including motile bacteria . SSY is commercially used as a highly absorbing (food) dye.…”

“…These surfactants have the same hydrophobic head group, which is substituted with an ethylene glycol tail of different lengths, which gives rise to a broad range of HLB values. In recent work, we added Triton X‐100 to properly align DSCG on a photopatterned hydrophobic substrate …”

“…While research on liquid crystals has strongly focused on LCD technology in the past decades, currently, many new and exciting applications are emerging that require novel materials properties and new engineering methods. The last decade has seen an increasing interest in synergizing unique LC characteristics with aqueous environments, for instance, for the development of biological sensing applications, (biocompatible) templates which align and manipulate (living) anisotropic materials, and highly dichroic LCs for facile fabrication of optical elements …”

Bioinspired Nanocomposite Hydrogels with Highly Ordered Structures

“…[110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126] For example, the chiral nematic liquid crystal phase of a 1D rod-like virus can act as a template to enable its self-assembly in the presence of monomers, crosslinkers, and initiators. [112] After polymerization and etching away the virus templates, aligned hydrogels remain.…”

Designs of Plasmonic Metamasks for Photopatterning Molecular Orientations in Liquid Crystals

“…Another development is to use curvilinear nanogrooves generated on polyimide films by tips of an atomic force microscope [25]. Recent studies have also extended the photoalignment techniques to lyotropic LC systems [19,26]. These techniques are ideal for research purposes and fast device prototyping, but face challenges for large-scale manufacturing because of the serial nature of their processes or incapability to achieve arbitrary director fields in some cases.…”