A simple yet robust method for large‐area patterning of polymer films—capillary force lithography—is presented here. This method, which combines the essential features of imprint lithography and microcontact printing, allows the replication of features down to 100 nm. The Figure shows a typical pattern.

Mechanical buckling usually means catastrophic failure in structural mechanics systems. However, controlled buckling of thin films on compliant substrates has been used to advantage in diverse fields such as micro‐/nanofabrication, optics, bioengineering, and metrology as well as fundamental mechanics studies. In this Feature Article, a mechanical buckling model is presented, which sprang, in part, from the buckling study of high‐quality, single‐crystalline nanomaterials. To check the mechanical‐buckling phenomenon down to the nano‐/molecular scale, well‐aligned single‐walled carbon nanotube arrays and cross linked carbon‐based monolayers are transferred from growth substrate onto elastomeric substrate and then they are buckled into well‐defined shapes that are amenable to quantitative analysis. From this nano‐ or molecular‐scale buckling, it is shown that the mechanical moduli of nanoscale materials can easily be determined, even using a model based on continuum mechanics. In addition, buckling phenomena can be utilized for the determination of mechanical moduli of organic functional materials such as poly(3‐hexylthiophene) (P3HT) and P3HT/6,6‐phenyl‐C61‐butyric acid methyl ester (PCBM) composite, which are widely used for organic transistors and organic photovoltaics. The results provide useful information for the realization of flexible and/or stretchable organic electronics. Finally, the fabrication and applications of “wavy, stretchable” single‐crystal Si electronics on elastomeric substrates are demonstrated.

Mechanical moduli of common organic electronic materials are measured by the buckling method. The organic layers were prepared on the elastomer polydimethylsiloxane (PDMS) substrate by transfer, direct spin-coating, or thermal evaporation. When a small (∼2%) compressive strain is applied to organic/PDMS film samples, the layer becomes buckled with a characteristic wavelength. Fitting the experimentally measured data of buckling wavelength as a function of layer thickness with a model equation yields the mechanical modulus of the organic layer. The measured values compare well with those from theoretical predictions for materials such as poly(3-hexylthiophene) (P3HT) and its blend with [6,6]-phenyl C61-butyric acid methyl ether (PCBM). The modulus of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is similar to that of pure PSS, which is contrary to the common expectation that the ionic interaction between PEDOT and PSS chains may lead to a modulus value 2−3 times larger than that of the constituent polymers. The similarity is likely due to a very small amount of PEDOT added and the oligomeric nature of PEDOT. Thermally evaporated pentacene film has a modulus value of ∼15 GPa, which is an order of magnitude larger than those of other polymeric materials investigated here, and reveals delamination bukling behavior when the magnitude of compression is relatively large. The residual solvent in polyaniline (PANI) plays the role of plasticizer and leads to a very small modulus. The measured mechanical moduli of common organic electronic materials would be valuable for designing and implementing flexible and/or stretchable organic electronics.

We describe a novel UV-curable mold that is stiff enough for replicating dense sub-100-nm features even with a high aspect ratio. It also allows for flexibility when the mold is prepared on a flexible support such that large area replication can be accomplished. The composite material of the mold is inert to chemicals and solvents. The surface energy is made low with a small amount of releasing agent such that the mold can be removed easily and cleanly after patterning. In addition, the material allows self-replication of the mold. These unique features of the mold material should make the mold quite useful for various patterning purposes.

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