Reversible adhesion is the key functionality to grip, place, and release objects nondestructively. Inspired by nature, micropatterned dry adhesives are promising candidates for this purpose and have attracted the attention of research groups worldwide. Their enhanced adhesion compared to nonpatterned surfaces is frequently demonstrated. An important conclusion is that the contact mechanics involved is at least as important as the surface energy and chemistry. In this paper, the roles of the contact geometry and mechanical properties are reviewed. With a focus on applications, the effects of substrate roughness and of temperature variations, and the long-term performance of micropatterned adhesives are discussed. The paper provides a link between the current, detailed understanding of micropatterned adhesives and emerging applications. The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201800865.are designated for locomotion over various types of substrates, involving attachment and detachment within milliseconds. [1][2][3][4][5] It is of interest for evolutionary biologists that many foot pads are strikingly similar in morphology: elongated fibrillar structures with aspect ratios ranging from 10 to 80 leading to terminal elements with very different shapes (Figure 1a and Figure 3). [6][7][8][9] For some animals such as the gecko, the adhesive ability of their toe pads can be attributed to van der Waals interactions and, to some extent, to capillary forces. [10][11][12][13][14][15] In the gecko, the fibrillar pads are composed of millions of keratinous hairs (called setae) that branch into even finer terminal elements (spatulae) (Figure 1a). [16,17] Such a hierarchically organized structure results in a soft and compliant surface, which allows easy adaption to roughness at the expense of little strain energy and thus enhances adhesion.More than 1000 reports published in the field of bioinspired dry adhesives over the last two decades reflect a considerable interest in resolving the underlying adhesion mechanisms, e.g., refs. [18][19][20][21]. Application-oriented publications were motivated by a strong interest in creating novel gripper devices and pickand-place systems (Figure 1b), e.g., refs. [18-20] and [22][23][24], climbing robots for terrestrial and extraterrestrial activities, [25][26][27][28][29][30][31][32] new gasket designs in microfluidics, [33,34] or novel solutions for biomedical applications. [35][36][37][38] The present feature article aims to describe the path from fundamental considerations, including a detailed understanding of the relevant contact mechanics, to emerging applications. It is now known that the success of mimicking micropatterned dry adhesives critically depends on the interplay between design parameters, such as dimensions of the structure elements and the terminal tip-shape geometry, and the bulk and surface properties of the materials in contact. How these parameters control the adhesive performance of synthetic...

Monodisperse, size-controlled Ni-P nanoparticles were synthesised in a single step process using triphenyl-phosphane (TPP), oleylamine (OA), and Ni(II)acetyl-acetonate. The nanoparticles were amorphous, contained ~30 at% P and their size was controlled between 7-21 nm simply by varying the amount of TPP. They are catalytically active for tailored carbon nanotube growth.

A method for the postdeposition organic coating of metallic nanoparticles is introduced. FePt nanoparticles from the gas phase are deposited onto Si substrates which are pre-coated with multilayers of phospholipid molecules by spin coating. If the substrate temperature is just below or above the temperature, at which the phospholipids undergo a phase transition from the liquid crystalline into an intermediate phase, the particles are enwrapped by the lipids. The particles exhibit a clear tendency to self-assemble in regular two-dimensional particle arrangements.

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We describe here a chemically controlled pathway for the designed synthesis of iron oxide nanoparticles by thermal decomposition of iron(II) and iron(III) oxalates in high-boiling solvents in the presence of oleylamine and oleic acid acting as capping ligands. The phase composition of the nanocrystals (Fe, FeO, Fe 3 O 4 , or α-Fe 2 O 3 ) could be precisely controlled by adjusting the synthesis conditions or by addition of appropriate oxidants, such as trimethylamine-N-oxide (TMAO), which produced highly monodisperse iron(III) oxide particles in the range of 6−25 nm in good yields. The decomposition behavior of different precursor/ TMAO mixtures was elucidated by differential scanning calorimetry and thermogravimetry, and resulting particles were characterized by comprehensive HR-TEM and XRD analyses.

Micro-objects stick tenaciously to each other—a well-known show-stopper in microtechnology and in handling micro-objects. Inspired by the trigger plant, we explore a mechanical metastructure for overcoming adhesion involving a snap-action mechanism. We analyze the nonlinear mechanical response of curved beam architectures clamped by a tunable spring, incorporating mono- and bistable states. As a result, reversible miniaturized snap-through devices are successfully realized by micron-scale direct printing, and successful pick-and-place handling of a micro-object is demonstrated. The technique is applicable to universal scenarios, including dry and wet environment, or smooth and rough counter surfaces. With an unprecedented switching ratio (between high and low adhesion) exceeding 10 4 , this concept proposes an efficient paradigm for handling and placing superlight objects.

For the next generation of handling systems, reversible adhesion enabled by micropatterned dry adhesives exhibits high potential. The versatility of polymeric micropatterns in handling objects made from various materials has been demonstrated by several groups. However, specimens reported in most studies have been restricted to the laboratory scale. Upscaling the size and quantity of micropatterned adhesives is the next step to enable successful technology transfer. Towards this aim, we introduce a continuous roll-to-roll replication process for fabrication of high-performance, mushroom-shaped micropatterned dry adhesives. The micropatterns were made from UV-curable polyurethane acrylates. To ensure the integrity of the complex structure during the fabrication process, flexible templates were used. The compression between the template and the wet prepolymer coating was investigated to optimize replication results without structural failures, and hence, to improve adhesion. As a result, we obtained micropatterned adhesive tapes, 10 cm in width and several meters in length, with adhesion strength about 250 kPa to glass, suitable for a wide range of applications.

A total of 81 doped and undoped anatase nano-particles were synthesised by a precipitation/co-precipitation process followed by a hydrothermal treatment to obtain increased visible light photocatalytic activity. The screening process was performed utilising a high throughput analysis system based on the photometric monitoring of the photocatalytic degradation of organic dyes (Rhodamine B, Malachite Green, Acid Blue 29). Photocatalytically active coatings were prepared with selected catalysts with high and low rankings from the screening. Degradation experiments with stearic acid could confirm the varying grades of visible light activity as seen in the screening process.