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Structures for biomimetic, fluidic, and biological applications
Stratakis, Emmanuel,Jeon, Hojeong,Koo, Sangmo MRS MATERIALS RESEARCH SOCIETY 2016 MRS bulletin Vol.41 No.12
<P>Controlling the interactions of light with matter is crucial for the success and scalability of materials-processing applications. When ultrashort pulsed lasers are used, the optimal interplay between the laser and the material parameters enable highly precise and controllable fabrication, allowing structuring down to the nanometer scale. Besides this, a unique aspect for many applications is the possibility of material modifications at multiple length scales, leading to complex micro- and nanoscale architectures, while adding a new dimension to optimization of the structures. As a result, femtosecond laser micro-/nanoprocessing offers unique capabilities for three-dimensional, material-independent modification, opening new opportunities for innovation and exploitation in the materials industry. This article focuses on the implementation of ultrashort pulsed laser-based micro- and nanofabrication methodologies for the realization of structures relevant to biomimetic, fluidic, and biological applications. The wealth of possibilities and the number of new approaches for obtaining complex high-resolution features at the micro- and nanoscales are demonstrated.</P>
Yoo, Jae-Hyuck,Kim, Eunpa,Hwang, David J. MRS MATERIALS RESEARCH SOCIETY 2016 MRS bulletin Vol.41 No.12
<P>This article summarizes recent research on laser-based processing of two-dimensional (2D) atomic layered materials, including graphene and transition-metal dichalcogenides (TMDCs). Ultrafast lasers offer unique processing routes that take advantage of distinct interaction mechanisms with 2D materials to enable extremely localized energy deposition. Experiments have shown that ablative direct patterning of graphene by ultrafast lasers can achieve resolutions of tens of nanometers, as well as single-step pattern transfer. Ultrafast lasers also induce non-thermal excitation mechanisms that are useful for the thinning of TMDCs to tune the 2D material bandgap. Laser-assisted site-specific doping was recently demonstrated and ultrafast laser radiation under ambient air environment could be used for the direct writing of high-quality graphene patterns on insulating substrates. This article concludes with an outlook on developing further advanced laser processing with scalability, in situ monitoring strategies, and potential applications.</P>
Mechanisms and theoretical simulations of the catalytic growth of nanocarbons
Penev, Evgeni S.,Ding, Feng,Yakobson, Boris I. MRS MATERIALS RESEARCH SOCIETY 2017 MRS bulletin Vol.42 No.11
<P>Nanocarbons have been catalytically grown since 1993. However, even today, the formation mechanisms of carbon nanotubes (CNTs) and graphene are not sufficiently understood. This sustained challenge has been an engine for the development in theory concepts and computational methods, tackling the problem of well-controlled production of these nanomaterials. This article discusses how experimental discoveries and theoretical approaches evolved hand-in-hand for the successful understanding of challenging issues, highlighting parallels and distinctions between graphene and CNTs. Key aspects include the mechanisms of nucleation and CNT-liftoff, chiral symmetry selection and control, rates of growth and island shapes, mechanisms defining single chirality of the nanotubes, and ways to suppress grain boundaries in the quest for ever larger and faster growing single-crystal graphene, or longest defect-free CNTs. The theme of catalyst chemistry and structure, either as a nanoparticle or a planar substrate, is traced through the stages of nanocarbon formation, with focus on theoretically generalizable findings.</P>