Browsing by Author "Thomas, Edwin L."
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Item 25th Anniversary Article: Ordered Polymer Structures for the Engineering of Photons and Phonons(Wiley, 2014) Lee, Jae-Hwang; Koh, Cheong Yang; Singer, Jonathan P.; Jeon, Seog-Jin; Maldovan, Martin; Stein, Ori; Thomas, Edwin L.The engineering of optical and acoustic material functionalities via construction of ordered local and global architectures on various length scales commensurate with and well below the characteristic length scales of photons and phonons in the material is an indispensable and powerful means to develop novel materials. In the current mature status of photonics, polymers hold a pivotal role in various application areas such as light-emission, sensing, energy, and displays, with exclusive advantages despite their relatively low dielectric constants. Moreover, in the nascent field of phononics, polymers are expected to be a superior material platform due to the ability for readily fabricated complex polymer structures possessing a wide range of mechanical behaviors, complete phononic bandgaps, and resonant architectures. In this review, polymer-centric photonic and phononic crystals and metamaterials are highlighted, and basic concepts, fabrication techniques, selected functional polymers, applications, and emerging ideas are introduced.Item 3D touchless multiorder reflection structural color sensing display(American Association for the Advancement of Science, 2020) Kang, Han Sol; Han, Sang Won; Park, Chanho; Lee, Seung Won; Eoh, Hongkyu; Baek, Jonghyeok; Shin, Dong-Gap; Park, Tae Hyun; Huh, June; Lee, Hyungsuk; Kim, Dae-Eun; Ryu, Du Yeol; Thomas, Edwin L.; Koh, Won-Gun; Park, CheolminThe development of a lightweight, low-power, user-interactive three-dimensional (3D) touchless display in which a human stimulus can be detected and simultaneously visualized in noncontact mode is of great interest. Here, we present a user-interactive 3D touchless sensing display based on multiorder reflection structural colors (SCs) of a thin, solid-state block copolymer (BCP) photonic crystal (PC). Full-visible-range SCs are developed in a BCP PC consisting of alternating lamellae, one of which contains a chemically cross-linked, interpenetrated hydrogel network. The absorption of a nonvolatile ionic liquid into the domains of the interpenetrated network allows for further manipulation of SC by using multiple-order photonic reflections, giving rise to unprecedented visible SCs arising from reflective color mixing. Furthermore, by using a hygroscopic ionic liquid ink, a printable 3D touchless interactive display is created where 3D position of a human finger is efficiently visualized in different SCs as a function of finger-to-display distance.Item Alternating Gyroid Network Structure in an ABC Miktoarm Terpolymer Comprised of Polystyrene and Two Polydienes(MDPI, 2020) Moschovas, Dimitrios; Manesi, Gkreti-Maria; Karydis-Messinis, Andreas; Zapsas, George; Ntetsikas, Konstantinos; Zafeiropoulos, Nikolaos E.; Piryazev, Alexey A.; Thomas, Edwin L.; Hadjichristidis, Nikos; Ivanov, Dimitri A.; Avgeropoulos, ApostolosThe synthesis, molecular and morphological characterization of a 3-miktoarm star terpolymer of polystyrene (PS, Mn = 61.0 kg/mol), polybutadiene (PB, Mn = 38.2 kg/mol) and polyisoprene (PI, Mn = 29.2 kg/mol), corresponding to volume fractions (φ) of 0.46, 0.31 and 0.23 respectively, was studied. The major difference of the present material from previous ABC miktoarm stars (which is a star architecture bearing three different segments, all connected to a single junction point) with the same block components is the high 3,4-microstructure (55%) of the PI chains. The interaction parameter and the degree of polymerization of the two polydienes is sufficiently positive to create a three-phase microdomain structure as evidenced by differential scanning calorimetry and transmission electron microscopy (TEM). These results in combination with small-angle X-ray scattering (SAXS) and birefringence experiments suggest a cubic tricontinuous network structure, based on the I4132 space group never reported previously for such an architecture.Item Anatomy of triply-periodic network assemblies: characterizing skeletal and inter-domain surface geometry of block copolymer gyroids(Royal Society of Chemistry, 2018) Prasad, Ishan; Jinnai, Hiroshi; Ho, Rong-Ming; Thomas, Edwin L.; Grason, Gregory M.Triply-periodic networks (TPNs), like the well-known gyroid and diamond network phases, abound in soft matter assemblies, from block copolymers (BCPs), lyotropic liquid crystals and surfactants to functional architectures in biology. While TPNs are, in reality, volume-filling patterns of spatially-varying molecular composition, physical and structural models most often reduce their structure to lower-dimensional geometric objects: the 2D interfaces between chemical domains; and the 1D skeletons that thread through inter-connected, tubular domains. These lower-dimensional structures provide a useful basis of comparison to idealized geometries based on triply-periodic minimal, or constant-mean curvature surfaces, and shed important light on the spatially heterogeneous packing of molecular constituents that form the networks. Here, we propose a simple, efficient and flexible method to extract a 1D skeleton from 3D volume composition data of self-assembled networks. We apply this method to both self-consistent field theory predictions as well as experimental electron microtomography reconstructions of the double-gyroid phase of an ABA triblock copolymer. We further demonstrate how the analysis of 1D skeleton, 2D inter-domain surfaces, and combinations therefore, provide physical and structural insight into TPNs, across multiple length scales. Specifically, we propose and compare simple measures of network chirality as well as domain thickness, and analyze their spatial and statistical distributions in both ideal (theoretical) and non-ideal (experimental) double gyroid assemblies.Item Asymmetric diffraction from two-component optical gratings made of passive and lossy materials(The Optical Society, 2016) Liang, Guanquan; Abouraddy, Ayman; Christodoulides, Demetrios; Thomas, Edwin L.Diffraction with asymmetric enhancement and suppression, and alternating contrast for symmetric diffraction orders is demonstrated from planar two-component optical gratings made of passive/lossy materials. Simulations agree well with the experimental diffraction pattern of the fabricated sample. Our fabrication approach uses simple, standard planar micro/nano lithography employing one photoresist and one dye. No 3D profiling is needed. The phenomena is due to the left-right asymmetric material distribution in the periodic grating, which gives rise to non-reciprocal light coupling for diffraction to the positive and negative orders.Item Effect of Versatile Structural Design on Properties and Applications of Two-Dimensional Conjugated Microporous Polymer Thin Films(2021-12-03) Miller, Kristen A.; Ajayan, Pulickel M.; Thomas, Edwin L.Microporous two-dimensional (2D) polymers have great potential in many applications given their covalent bonding in two dimensions, extended conjugated structures, high surface areas and functional design. However, their widespread implementation in practical application spaces has so far been limited by the lack of facile and scalable processing methods from their generally insoluble forms. In this work, the inspiration for structural design is drawn from the molecular construct of high-strength, high-modulus 1D polymers that have produced some of the strongest materials to date, particularly poly(p-phenylene-2,6-benzobisoxazole) (PBO) or Zylon. Herein, a series of novel solvothermal bottom-up methods were developed to directly synthesize 2D covalently linked polymer films from starting material solutions. Benzoxazole-linked films were produced via a two-step process that allows the deposition of a uniform intermediate film network via reversible, non-covalent interactions, followed by a subsequent solid-state annealing step that facilitates the irreversible conversion to the desired polymer product. The versatility of this synthesis method is demonstrated by producing films with four different aromatic core units. Slight modification of the synthetic methods enables the direct synthesis of reversibly linked imine and hydrazone-based films using a metal triflate catalyst with a single processing step. The resulting 2D polymer films are amorphous yet demonstrate microporosity and an anisotropic layered morphology that can be exfoliated into few-layer nanosheets. The hydrazone-linked films exhibit more compact planar stacking and bright photoluminescence due to the constrained planar conformation induced by intramolecular hydrogen-bonding. These 2D polymer films are comprised of highly aromatic, conjugated building blocks providing an opportunity to translate the mechanical performance of classic rigid-rod 1D polymers across a plane by extending covalent bonding into two dimensions, while simultaneously reducing density. The demonstrated mechanical properties from tensile testing and nanoindentation show axial tensile and transverse compressive elastic moduli on the scale of several GPa, rivalling the performance of solution-cast films of 1D PBO, as well as several other 1D high-strength polymer films. The structural effect of linkage chemistry is compared via nanoindentation, showing that the benzoxazole-linked films exhibit higher modulus and hardness relative to the more compliant reversibly linked counterparts.Item Extreme Energy Dissipation via Material Evolution in Carbon Nanotube Mats(Wiley, 2021) Hyon, Jinho; Lawal, Olawale; Thevamaran, Ramathasan; Song, Ye Eun; Thomas, Edwin L.Thin layered mats comprised of an interconnected meandering network of multiwall carbon nanotubes (MWCNT) are subjected to a hypersonic micro-projectile impact test. The mat morphology is highly compliant and while this leads to rather modest quasi-static mechanical properties, at the extreme strain rates and large strains resulting from ballistic impact, the MWCNT structure has the ability to reconfigure resulting in extraordinary kinetic energy (KE) absorption. The KE of the projectile is dissipated via frictional interactions, adiabatic heating, tube stretching, and ultimately fracture of taut tubes and the newly formed fibrils. The energy absorbed per unit mass of the film can range from 7–12 MJ kg−1, much greater than any other material.Item High-velocity projectile impact induced 9R phase in ultrafine-grained aluminium(Springer Nature, 2017) Xue, Sichuang; Fan, Zhe; Lawal, Olawale B.; Thevamaran, Ramathasan; Li, Qiang; Liu, Yue; Yu, K.Y.; Wang, Jian; Thomas, Edwin L.; Wang, Haiyan; Zhang, XinghangAluminium typically deforms via full dislocations due to its high stacking fault energy. Twinning in aluminium, although difficult, may occur at low temperature and high strain rate. However, the 9R phase rarely occurs in aluminium simply because of its giant stacking fault energy. Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nm in width in ultrafine-grained aluminium with an average grain size of 140 nm, as confirmed by extensive post-impact microscopy analyses. The stability of the 9R phase is related to the existence of sessile Frank loops. Molecular dynamics simulations reveal the formation mechanisms of the 9R phase in aluminium. This study sheds lights on a deformation mechanism in metals with high stacking fault energies.Item Host-Guest Self-assembly in Block Copolymer Blends(Springer Nature, 2013) Park, Woon Ik; Kim, YongJoo; Jeong, Jae Won; Kim, Kyungho; Yoo, Jung-Keun; Hur, Yoon Hyung; Kim, Jong Min; Thomas, Edwin L.; Alexander-Katz, Alfredo; Jung, Yeon SikUltrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs.Item Impact of Geometry on the TM Photonic Band Gaps of Photonic Crystals and Quasicrystals(American Physical Society, 2011) Jia, Lin; Bita, Ion; Thomas, Edwin L.Here we demonstrate a novel quantitative procedure to pursue statistical studies on the geometric properties of photonic crystals and photonic quasicrystals (PQCs) which consist of separate dielectric particles. The geometric properties are quantified and correlated to the size of the photonic band gap (PBG) for wide permittivity range using three characteristic parameters: shape anisotropy, size distribution, and feature-feature distribution. Our concept brings statistical analysis to the photonic crystal research and offers the possibility to predict the PBG from a morphological analysis.Item Networks with controlled chirality via self-assembly of chiral triblock terpolymers(AAAS, 2020) Wang, Hsiao-Fang; Chiu, Po-Ting; Yang, Chih-Ying; Xie, Zhi-Hong; Hung, Yu-Chueh; Lee, Jing-Yu; Tsai, Jing-Cherng; Prasad, Ishan; Jinnai, Hiroshi; Thomas, Edwin L.; Ho, Rong-MingNanonetwork-structured materials can be found in nature and synthetic materials. A double gyroid (DG) with a pair of chiral networks but opposite chirality can be formed from the self-assembly of diblock copolymers. For triblock terpolymers, an alternating gyroid (GA) with two chiral networks from distinct end blocks can be formed; however, the network chirality could be positive or negative arbitrarily, giving an achiral phase. Here, by taking advantage of chirality transfer at different length scales, GA with controlled chirality can be achieved through the self-assembly of a chiral triblock terpolymer. With the homochiral evolution from monomer to multichain domain morphology through self-assembly, the triblock terpolymer composed of a chiral end block with a single-handed helical polymer chain gives the chiral network from the chiral end block having a particular handed network. Our real-space analyses reveal the preferred chiral sense of the network in the GA, leading to a chiral phase.Item Optical forces and optical torques on various materials arising from optical lattices in the Lorentz-Mie regime(American Physical Society, 2011) Jia, Lin; Thomas, Edwin L.By combining the Maxwell stress tensor with the finite-difference time-domain (FDTD) method, we calculate the optical force and optical torque on particles from optical lattices. We compare our method to the two-component method and the electrostatic approximation (ESA). We also discuss how particle's refractive index, shape, size, and the morphology of an optical lattice influence optical forces and the condition to form stable optical trapping wells. In addition to optical forces, optical torque from one dimensional (1D) optical lattice is discussed for particles having anisotropic shapes; metastable and stable equilibrium orientation states are found. A detailed understanding of the optical force and torque from optical lattices has significant implications for optical trapping, micromanipulation, and sorting of particles.Item Photonic density of states of two-dimensional quasicrystalline photonic structures(American Physical Society, 2011) Jia, Lin; Bita, Ion; Thomas, Edwin L.A large photonic band gap (PBG) is highly favorable for photonic crystal devices. One of the most important goals of PBG materials research is identifying structural design strategies for maximizing the gap size. We provide a comprehensive analysis of the PBG properties of two-dimensional (2D) quasicrystals (QCs), where rotational symmetry, dielectric fill factor, and structural morphology were varied systematically in order to identify correlations between structure and PBG width at a given dielectric contrast (13:1, Si:air). The transverse electric (TE) and transverse magnetic (TM) PBGs of 12 types of QCs are investigated (588 structures). We discovered a 12mm QC with a 56.5% TE PBG, the largest reported TE PBG for an aperiodic crystal to date. We also report here a QC morphology comprising “throwing star”-like dielectric domains, with near-circular air cores and interconnecting veins emanating radially around the core. This interesting morphology leads to a complete PBG of ∼20% , which is the largest reported complete PBG for aperiodic crystals.Item Rapid fabrication of 3D terahertz split ring resonator arrays by novel single-shot direct write focused proximity field nanopatterning(Optical Society of America, 2012) Singer, Jonathan P.; Lee, Jae-Hwang; Kooi, Steven E.; Thomas, Edwin L.For the next generation of phoXonic, plasmonic, optomechanical and microfluidic devices, the capability to create 3D microstructures is highly desirable. Fabrication of such structures by conventional top-down techniques generally requires multiple timeconsuming steps and is limited in the ability to define features spanning multiple layers at prescribed angles. 3D direct write lithography (3DDW) has the capability to draw nearly arbitrary structures, but is an inherently slow serial writing process. Here we present a method, denoted focused proximity field nanopatterning (FPnP), that combines 3DDW with single or multiphoton interference lithography (IL). By exposing a thick photoresist layer having a phase mask pattern imprinted on its surface with a tightly focused laser beam, we produce locally unique complex structures. The morphology can be varied based on beam and mask parameters. Patterns may be written rapidly in a single shot mode with arbitrary positions defined by the direct write, thus exploiting the control of 3DDW with the enhanced speed of phase mask IL. Here we show the ability for this technique to rapidly produce arrays of “stand-up” far IR resonators.Item Two-pattern compound photonic crystals with a large complete photonic band gap(American Physical Society, 2011) Jia, Lin; Thomas, Edwin L.We present a set of two-dimensional aperiodic structures with a large complete photonic band gap (PBG), which are named two-pattern photonic crystals. By superposing two substructures without regard to registration, we designed six new aperiodic PBG structures having a complete PBG larger than 15% for ɛ2/ɛ1=11.4. The rod-honeycomb two-pattern photonic crystal provides the largest complete PBG to date. An aperiodic structure becomes the champion structure with the largest PBG. Surprisingly, the TM and TE gaps of a two-pattern photonic crystal are much less interdependent than the PBGs of conventional photonic crystals proposed before, affording interesting capabilities for us to tune the TM and TE PBGs separately. By altering the respective substructures, optical devices for different polarizations (TE, TM, or both) can readily be designed.Item Visualizing the double-gyroid twin(National Academy of Sciences, 2021) Feng, Xueyan; Zhuo, Mujin; Guo, Hua; Thomas, Edwin L.Periodic gyroid network materials have many interesting properties (band gaps, topologically protected modes, superior charge and mass transport, and outstanding mechanical properties) due to the space-group symmetries and their multichannel triply continuous morphology. The three-dimensional structure of a twin boundary in a self-assembled polystyrene-b-polydimethylsiloxane (PS-PDMS) double-gyroid (DG) forming diblock copolymer is directly visualized using dual-beam scanning microscopy. The reconstruction clearly shows that the intermaterial dividing surface (IMDS) is smooth and continuous across the boundary plane as the pairs of chiral PDMS networks suddenly change their handedness. The boundary plane therefore acts as a topological mirror. The morphology of the normally chiral nodes and strut loops within the networks is altered in the twin-boundary plane with the formation of three new types of achiral nodes and the appearance of two new classes of achiral loops. The boundary region shares a very similar surface/volume ratio and distribution of the mean and Gaussian curvatures of the IMDS as the adjacent ordered DG grain regions, suggesting the twin is a low-energy boundary.