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SERS substrates were fabricated through self-assembly of gold nanoparticles upon solution-drying in a periodic confining structure. The technique leads to uniform, parallel linear nanoparticle arrays with the precise arrangement defined through the dimensions of the particles and the grooves, which provide high and uniform SERS enhancement over extended areas.

We report on a novel lithography-free method for obtaining chemical submicron patterns of macromolecules on flat substrates. The approach is an advancement of the well-known microcontact printing scheme: While for classical microcontact printing lithographically produced masters are needed, we show that controlled wrinkling can serve as an alternative pathway to producing such masters. These can even show submicron periodicities. We expect upscaling to larger areas to be considerably simpler than that for existing techniques, as wrinkling results in a macroscopic deformation process that is not limited in terms of substrate size. Using this approach, we demonstrate successful printing of aqueous solutions of polyelectrolytes and proteins. We study the effectiveness of the stamping process and its limits in terms of periodicities and heights of the stamps' topographical features. We find that critical wavelengths are well below 355 nm and critical amplitudes are below 40 nm and clarify the failure mechanism in this regime. This will permit further optimization of the approach in the future.

We created hierarchically ordered structures of nanoparticles on smooth plan ar hydrophilic substrates by drying colloidal dispersions in confinement under macroscopic stamps with microscopically wrinkled surfaces. Experiments were carried out with model nanoparticle suspensions that possess high colloidal stability and monodispersity. The structures ranged from single parallel lines of particles to arrays of dense prismatic ridges. The type of observed structure could be controlled by the particle concentration in the initial dispersion. Confinement between two crossed stamps led to interconnected meshes of particles. The precise morphology could be predicted in all cases by Monte Carlo computer simulations of confined hard spheres. Our findings open up possibilities for versatile nanoparticle assembly on surfaces. Ordered arrays of nanoparticles form excellent candidates for components of future optical, electronic and magnetic devices, '.2 for creating biomimetic surfaces,' and for exploiting their plasmonic properties,,• 5 Control of the precise placement of the particles on asolid surface is a prereq uisite for the technological use of the uniq ue, size-specific properties of the nanoparticles. Primary strategies for controlling the spatial arrangement ofmuch larger, micron-sized colloids include the deposition of particle monolayers on chemically or topographically structured substrates/>-9 epitaxial growth ' 0." and confinement. '2.13 Structures with periodicities comparable to the wavelength of visible light are interesting as these enable one to make use of their optical band structure. In particular, linear assemblies, such as particle wires, ' 4, ' 5 possess high potential for photonic applieations. Nevertheless, both structuring on the smaller (nano) scale, as weil as obtaining macroscopic coverage of the substrate is desirable in attempting to bridge all length-scales. Both physical 6 ,9 and chemicaF,8 properties of surfaces can be used in order to create templates for the adsorption of particles. Topographic templates can be produced using photolithographic•,2 and soft lithographic•6-•8 techniques or, altematively, by controlled wrinkling.' 9 ,w Wrinkles with well-defined wavelength form if an elastomeric substrate that is coated with a thin, hard layer is exposed to a lateral compressive strain?' Significant benefits of this approach are its low cost and the simplicity of scaling up the size of the structured substrate to macroscopic dimensions.

This highlight focuses on recent advances in controlling inter-nanoparticle coupling effects by template-assisted organization of colloidal particles. We show that the use of templates formed by wrinkling allows circumventing drawbacks of classical lithographic approaches for template formation like the large number of processing steps and poor scalability. Subsequently, we illustrate that confinement effects can be used for creating particle assemblies with excellent short and long range order. This allows controlling inter-particle coupling effects. As an example, we focus on plasmonic coupling in gold nanoparticle arrays. We demonstrate that these arrays can be applied to develop efficient and homogenous substrates for surface enhanced Raman scattering (SERS).

We present a novel method to align the tobacco mosaic virus (TMV) on topographically structured surfaces. In order to gain defined patterns we use wrinkled polydimethlysiloxane (PDMS) sheets as templates. We aligned the virus with a simple spin-coating procedure on the PDMS sheet. The concentration of the virus solution and the spin speed are varied in order to identify ideal conditions for the arrangement of the viruses on the wrinkled templates. Here, we establish a simple analytical approach which allows quantifying the degree of order of the patterns, which is the basis for a quantitative discussion of templating efficiency. Furthermore, we discuss the role of dewetting processes for the particle assembly. TMVs can be used as reactive nanoparticles due to their well-defined surface chemistry. They can as well serve as a model system for alignment of anisotropic particles via spin coating from solution.

SUMMARY The influence of surface roughness on the attachment ability of insects has been repeatedly reported. In previous experiments, complex surface topographies were used as test substrates, whereas periodical structures have so far been neglected. In the present study, traction experiments with adult beetles Gastrophysa viridula and Leptinotarsa decemlineata were carried out to study the influence of surfaces, structured with periodical wrinkles, on insect attachment. Force measurements were carried out on male and female insects, both intact and after removal of claws, performing tethered walking on five polydimethylsiloxane substrates: (i) smooth, non-structured (control), (ii–v) structured with wrinkles of different wavelengths (366, 502, 911 and 25,076 nm). In two test series, beetles walked either perpendicular or parallel to the wrinkle alignment. Adults of G. viridula produced generally higher forces than those of L. decemlineata. The results show that the alignment of wrinkles had no significant influence on the force generation by beetles, probably because of the skewed position of their tarsomeres relative to the substrates. In both sexes, the highest force values were obtained on surfaces with wrinkles of 25 μm wavelength. On other wrinkled substrates, forces were significantly reduced in both males and females compared with the smooth, flat control, with the minimum force achieved on wrinkles with a wavelength of 911 nm.

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