http://oar.a-star.edu.sg:80/jspui/handle/123456789/112 Sat, 24 Jun 2017 19:00:38 GMT 2017-06-24T19:00:38Z http://oar.a-star.edu.sg:80/jspui/handle/123456789/1273 Title: Metal hierarchical patterning by direct nanoimprint lithography Authors: Su Hui, Lim; Radha, Boya; Saifullah, Mohammad S. M.; Kulkarni, Giridhar U. Abstract: Three-dimensional hierarchical patterning of metals is of paramount importance in diverse fields involving photonics, controlling surface wettability and wearable electronics. Conventionally, this type of structuring is tedious and usually involves layer-by-layer lithographic patterning. Here, we describe a simple process of direct nanoimprint lithography using palladium benzylthiolate, a versatile metal-organic ink, which not only leads to the formation of hierarchical patterns but also is amenable to layer-by-layer stacking of the metal over large areas. The key to achieving such multi-faceted patterning is hysteretic melting of ink, enabling its shaping. It undergoes transformation to metallic palladium under gentle thermal conditions without affecting the integrity of the hierarchical patterns on micro- as well as nanoscale. A metallic rice leaf structure showing anisotropic wetting behavior and woodpile-like structures were thus fabricated. Furthermore, this method is extendable for transferring imprinted structures to a flexible substrate to make them robust enough to sustain numerous bending cycles. Thu, 28 Feb 2013 00:00:00 GMT http://oar.a-star.edu.sg:80/jspui/handle/123456789/1273 2013-02-28T00:00:00Z http://oar.a-star.edu.sg:80/jspui/handle/123456789/1270 Title: Tunable daughter molds from a single Si master grating mold Authors: Su Hui, Lim; Shreya, Kundu; Ramakrishnan, Ganesan; Hussain, Hazrat; Saifullah, M. S. M; Hyunsoo, Yang; Ghim Wei, Ho; Charanjit S., Bhatia Abstract: After the cost of ownership of tool, the next significant cost involved in nanoimprint lithography is that of mold fabrication. The cost of mold fabrication is proportional to the area of pattern and follows an inverse relationship with the pattern resolution. In this work, the authors demonstrate proof-of-concept fabrication of Si and SiO2 grating molds of variable feature sizes, spacings, densities, and aspect ratios that can be generated from a single Si master mold of 2 lm line and space features. This process utilizes “SiO2 resin,” which can be imprinted via in situ thermal free radical polymerization. Heat-treatment of the patterned resin resulted in loss of organics, formation of SiOx and gave rise to known feature size reduction (65%). After the pattern transfer using SiOx as the etch mask, a Si daughter mold containing 0.7 lm wide gratings with 3.3 lm spacing was generated. The process of imprinting and heat-treatment was repeated using the daughter mold, which regenerated a mold that approximates the master mold feature profile. Our technique demonstrates that submicron-sized features can be achieved from Si molds containing micron-sized features and vice versa. Such flexibility may lead to substantial reduction in the cost of mold fabrication. Mon, 04 Aug 2014 00:00:00 GMT http://oar.a-star.edu.sg:80/jspui/handle/123456789/1270 2014-08-04T00:00:00Z http://oar.a-star.edu.sg:80/jspui/handle/123456789/1003 Title: Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array Authors: Liew, Weng Heng; Sharifzadeh Mirshekarloo, Meysam; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock Abstract: Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers. Tue, 12 May 2015 00:00:00 GMT http://oar.a-star.edu.sg:80/jspui/handle/123456789/1003 2015-05-12T00:00:00Z http://oar.a-star.edu.sg:80/jspui/handle/123456789/810 Title: Layer-by-Layer Assembled Multilayer Shells for Encapsulation and Release of Fragrance Authors: Sadovoy, Anton; Lomova, Maria; Antipina, Maria; Braun, Norbert; Sukhorukov, Gleb; Kiryukhin, Maxim Abstract: Layer-by-layer assembled shells are prospective candidates for encapsulation, stabilization, storage, and release of fragrances. A shell comprising four alternative layers of a protein and a polyphenol is employed to encapsulate the dispersed phase of a fragrance-containing oil-in-water emulsion. The model fragrance used in this work consists of 10 ingredients, covering a range of typically employed aroma molecules, all premixed in equal mass and with sunflower oil acting as the base. The encapsulated emulsion is stable after 2 months of storage at 4 °C as revealed by static light scattering and confocal laser scanning microscopy. Gas chromatography/mass spectrometry data show that the encapsulation efficiency of 8 out of 10 fragrance ingredients depends on the water solubility: the less water-soluble an ingredient, the more of it is encapsulated. The amount of these fragrance ingredients remaining encapsulated decreases linearly upon emulsion incubation at 40 °C and the multilayer shell does not hinder their release. The other two fragrance ingredients having the lowest saturation vapor pressure demonstrate sustained release over 5 days of incubation at 40 °C. The composition of released fragrance remains almost constant over 3 days of incubation, upon further incubation it becomes enriched with these two ingredients when others start to be depleted. Wed, 14 Aug 2013 00:00:00 GMT http://oar.a-star.edu.sg:80/jspui/handle/123456789/810 2013-08-14T00:00:00Z