DOCSLIB.ORG

Differential Plasmonic Sensors

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Differential Plasmonic Sensors Differential Plasmonic Sensors Mustafa FIRAT Department of Physics, Bilkent University, Ankara, 06800, Turkey Abstract – In this project we are aiming to fabricate a surface plasmon resonance sensor inside a microfluidic channel. Microfluidic systems provide simple means to control and manipulate fluids at micrometer scales. Integration of microfluidic systems and plasmon resonance sensors could provide very sensitive refractive index sensors with very small detection volume. In this project we will use a grating surface coated with a 50nm Ag layer will be used to excite surface plasmons. Furthermore we would like to improve detection sensitivity by performing a phase sensitive measurement. Introduction use gold, because of its dielectric properties. Also, gold does not react with The aim of this project is to generate a oxygen and its surface is not oxidized in sensor that can measure physical, chemical time. Since we need its surface in order to and biological properties of fluids. By generate a surface plasmon, the surface combining the special characteristics of should not be oxidized for a good sensing. surface plasmons and microfluidic These are basic advantages of using a gold channels, we can get information about the layer to generate a surface plasmon. fluids that flow inside the microchannels. First of all, we inject two fluids into the Indeed, there is a distinction between microchannels. For the first tries, we will surface plasmons and surface plasmon use water and 10% Ethylene Glycol polaritons. At the boundary of the metal, because they are both transparent and there there are a huge number of electrons due to is a sensible difference between their index the free electrons of the metal. Since these of refraction, so in their dielectric are not binded to nucleus, they can be constants. Dielectric constants of the oscillated easily with an external electric medium determine the resonance condition field. If we can apply correct frequency of the surface plasmon sensor. We will and give the correct energy with the correct take advantage of the laminar flow inside momentum to these free electrons, they the microchannels to change the medium start oscillating with an exact frequency. on the surface plasmon sensor. In order to Actually they generate a plane wave in this do so, we should know Reynolds number. electron sea. This is called surface plasmon. And if the surface plasmons are Surface Plasmon Resonance coupled with a photon, the resulting hybridized excitation is called a surface Surface plasmons, also known as surface plasmon polariton (SPP). And we will plasmon polaritons, are the surface generate SPPs by sending photons from a electromagnetic waves that propagate in a Helium-Neon laser. And the technique of direction parallel to the metal/dielectric (or excitation of surface plasmons by light is metal/vacuum) interface. [1] In our setup, denoted as a surface plasmon resonance we use gold as the metal surface and we (SPR) for planar surfaces. use water-10% Ethylene Glycol laminar flow as the dielectric surface. Since all the The electric field of a propagating metals have free electrons, actually surface electromagnetic wave, here our light beam plasmon can be generated with almost all coming from Helium-Neon laser, can be metals. The condition is; dielectric expressed as constant of the metal must be negative and most of the metals have this property. We $ʚ&ī3ͮ&ĭ5ͯh/ʛ (1) ̿ Ɣ ͙̿ͤ where k is the wave number and ω is the the coming photon, from eq (4). If we frequency of the wave. By solving equate k x and k SPP we get Maxwell's equations for the ͥ⁄ ͦ electromagnetic wave at an interface h TuTv (9) ͤͧ͟͢͝ Ɣ ʠ ʡ between two materials with relative TuͮTv h dielectric constants ε1 and ε2 (see figure 1) Here we can see that k 0 and cancels we get each other according to (7). Since this is the horizontal component of the total & & ĭu ƍ ĭv Ɣ 0 (2) momentum at the same time, we can add g Tu Tv factor of the grating to this equation and according to (5). And finally we get ͦ ͦ ͦ h ͟ ƍ ͟ Ɣ ʠ ʡ ͝ Ɣ 1,2 (3) T T ͥ⁄ ͦ Z 3 5$ $ ͧ͢͝ Ɣ ʠ u v ʡ ƍ ͡ (10) where c is the speed of light in the vacuum. TuͮTv Solving these two equations, the dispersion This angle is the plasmon angle for a relationship for a wave propagating on the plasmon that that will be take place surface is between gold - 10% Ethylene Glycol interface. The only thing that we should do ͥ⁄ ͦ is to obtain the correct angle that gives the h TuTv (4) correct momentum in x direction. ͟3 Ɣ ʠ ʡ TuͮTv From the property of the grating, this momentum is shifted by g factor of the grated surface. (5) ͟ Ɣ ͟3 ƍ ͛͡ Here, m is a positive integer that describes first, second, third... order shifting to the momentum (comes from the grating) and g is the g factor of the grating, given by Z (6) ͛ Ɣ Figure 1 : Coordinate system for two material where, λ is the wavelength of the coming interfaces and drawing of the vectors that were used photon and is the periodicity of the in equations 1, 2, 3, 4 and 8. grating. We used a grating that has a periodicity = 600 nm and we used Helium-Neon laser that has a wavelength 632,8 nm. By knowing the wavelength of Reynolds Number and Laminar Flow the Helium-Neon laser, we can get the momentum of the photons as Laminar flow occurs when a fluid flows in h parallel layers, with no disruption between (7) the layers. In fluid dynamics, laminar flow ͤ͟ Ɣ And one can get the horizontal component is a flow regime characterized by high of the momentum of the coming photon momentum diffusion and low momentum [2] from k 0. If k 0 is the total momentum of the convection. There can be small mixing coming photon, k x is the x component of k 0 at interference layer of the fluids due to that is horizontal to the propagation of the diffusion but there is no mixing due to SPP. We can find k x from k 0 easily by turbulence in laminar flow. Turbulent flow (8) is just opposite the laminar flow. To ͟3 Ɣ ͤͧ͟͢͝ And we know the momentum of the understand laminar flow in microchannels, surface plasmon that will be generated by we should examine Reynolds number at first. Reynolds number is an important parameter in the equations that describe photolithography technique. The gratings whether the flow will be laminar or that we use were fabricated by a graduate turbulent. It is a dimensionless number. student in the lab. Fabricating a grating is Reynolds number is about flow geometry. not a part of this project. Furthermore, The fluid properties; density and viscosity, there are several companies fabricating plus flow velocity and a characteristic such gratings. One can design the shape length or characteristic dimension and sizes of the gratings on the computer determine the Reynolds number. By and get them prepared to those companies. characteristic length or characteristic It is the easy way. dimension, we mean diameter, width, height... etc. For cylindrical shapes diameter is the characteristic dimension but since we have rectangular channels, we will use the height of the microchanells that is in the order of 100 µm. Having one dimension in µm is enough to see laminar flow easily. That’s why laminar flow can occur even with water in microchannels but it is very hard to observe a laminar flow in pipes in daily life. According to the definition, Reynolds number is given by ` (11) Figure 2 : Silicon masters used to mold elastomeric ͙͌ Ɣ [ Ɣ \ Ɣ \ microchannels. We have used pattered SU8 where: photoresist as a master. These masters were fabricated in the clean room by a graduate student in the lab. • V is the mean fluid velocity (m/s) • L is a characteristic length, (traveled length of fluid) (m) • µ is the dynamic viscosity of the Design of Microfluidic Channel fluid (Pa·s or N·s/m² or kg/m·s) • ν is the kinematic viscosity ( ν = µ / For design of microchannels, again we use ρ) (m²/s) silicon masters. These masters are prepared • ρ is the density of the fluid (kg/m³) with the same procedure as grating • Q is the volumetric flow rate (m³/s) masters. Photolithography technique is the • A is the pipe cross-sectional area most commonly used method. As shown in (m²) [3] figure 2, we get a silicon master that has a raise with height 100 µm. When we pour In our microchannels, if the Reynolds liquid Polydimethylsiloxane (PDMS) onto number is less than 2300, we get a laminar our master, and keep it on the hot plate at flow. 70 oC for one hour, PDMS becomes amorphous solid. And we get our microchannels at the bottom of this elastic PDMS structure. This is the upper part of Grating Fabrication the channels. We need a cover to the bottom of the channels so that water and We used silicon grating masters to get a ethanol will pass through. Also, this part is grating on our PDMS. These gratings are the layer where we will generate the SPs. periodic on the silicon master and the So, grating and the golden layer will be in periodicity of the grating is 600 nm. These this part. We coated this second layer of silicon grating masters are prepared by PDMS by gold with a thickness 50nm.
Load more

Recommended publications
  • Bose-Einstein Condensation Measurements and Superflow in Condensed Helium
    JLowTempPhys DOI 10.1007/s10909-013-0855-0 Bose-Einstein Condensation Measurements and Superflow in Condensed Helium H.R. Glyde Received: 9 November 2012 / Accepted: 18 January 2013 © Springer Science+Business Media New York 2013 Abstract We review the formulation and measurement of Bose-Einstein condensa- tion (BEC) in liquid and solid helium. BEC is defined for a Bose gas and subsequently for interacting systems via the one-body density matrix (OBDM) valid for both uni- form and non-uniform systems. The connection between the phase coherence created by BEC and superflow is made. Recent measurements show that the condensate frac- tion in liquid 4He drops from 7.25 ± 0.75 % at saturated vapor pressure (p ≈ 0) to 2.8 ± 0.2 % at pressure p = 24 bars near the solidification pressure (p = 25.3 bar). Extrapolation to solid densities suggests a condensate fraction in the solid of 1 % or less, assuming a frozen liquid structure such as an amorphous solid. Measurements in the crystalline solid have not been able to detect a condensate with an upper limit 4 set at n0 ≤ 0.3 %. Opportunities to observe BEC directly in liquid He confined in porous media, where BEC is localized to patches by disorder, and in amorphous solid helium is discussed. Keywords Solid · Liquid · Helium · BEC · OBDM · Neutron scattering 1 Introduction This article is part of a series motivated by reports of possible superfluidity in solid helium, initially in 2004 [1, 2]. Other articles in this series survey extensively the experiments and theory in this new field and the current status of the field.
    [Show full text]
  • Drug-Rich Phases Induced by Amorphous Solid Dispersion: Arbitrary Or Intentional Goal in Oral Drug Delivery?
    pharmaceutics Review Drug-Rich Phases Induced by Amorphous Solid Dispersion: Arbitrary or Intentional Goal in Oral Drug Delivery? Kaijie Qian 1 , Lorenzo Stella 2,3 , David S. Jones 1, Gavin P. Andrews 1,4, Huachuan Du 5,6,* and Yiwei Tian 1,* 1 Pharmaceutical Engineering Group, School of Pharmacy, Queen’s University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK; [email protected] (K.Q.); [email protected] (D.S.J.); [email protected] (G.P.A.) 2 Atomistic Simulation Centre, School of Mathematics and Physics, Queen’s University Belfast, 7–9 College Park E, Belfast BT7 1PS, UK; [email protected] 3 David Keir Building, School of Chemistry and Chemical Engineering, Queen’s University Belfast, Stranmillis Road, Belfast BT9 5AG, UK 4 School of Pharmacy, China Medical University, No.77 Puhe Road, Shenyang North New Area, Shenyang 110122, China 5 Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland 6 Simpson Querrey Institute, Northwestern University, 303 East Superior Street, 11th Floor, Chicago, IL 60611, USA * Correspondence: [email protected] (H.D.); [email protected] (Y.T.); Tel.: +41-446339049 (H.D.); +44-2890972689 (Y.T.) Abstract: Among many methods to mitigate the solubility limitations of drug compounds, amor- Citation: Qian, K.; Stella, L.; Jones, phous solid dispersion (ASD) is considered to be one of the most promising strategies to enhance D.S.; Andrews, G.P.; Du, H.; Tian, Y. the dissolution and bioavailability of poorly water-soluble drugs.
    [Show full text]
  • Characteristics of the Solid State and Differences Between Crystalline and Amorphous Solids
    IJRECE VOL. 7 ISSUE 2 Apr.-June 2019 ISSN: 2393-9028 (PRINT) | ISSN: 2348-2281 (ONLINE) Characteristics of the Solid State and Differences between Crystalline and Amorphous Solids Anu Assistant Professor, Department of Physics, Indus Degree college, Kinana Abstract: “A crystal is a solid composed of atoms (ions or possess the unique property of being rigid. Such solids are molecules) arranged in an orderly repetitive array.” Most of known as true solids e.g., NaCl, KCl, Sugar, Ag, Cu etc. the naturally occurring solids are found to have definite On the other hand the solid which loses shape on long crystalline shapes which can be recognized easily. These are standing, flows under its own weight and is easily distorted by in large size because these are formed very slowly, thus even mild distortion force, is called pseudo solid e.g., glass, particles get sufficient time to get proper position in the pith etc. Some solids such as NaCl, sugar, sulphur etc. have crystal structure. Some crystalline solids are so small that properties not only of rigidity and incompressibility but also appear to be amorphous. But on examination under a powerful of having typical geometrical forms. These solids are called microscope they are also found to have a definite crystalline crystalline solids. In such solids there is definite arrangement shape. Such solids are known as micro-crystalline solids. of particles (atoms, ions or molecules) throughout the entire three dimensional network of a crystal. This is named as long- Key Words: Crystal, Goniometer, Amorphous solids range order. This three dimensional arrangement is called crystal lattice or space lattice.
    [Show full text]
  • Irreversible Transition of Amorphous and Polycrystalline Colloidal Solids Under Cyclic Deformation
    PHYSICAL REVIEW E 98, 062607 (2018) Irreversible transition of amorphous and polycrystalline colloidal solids under cyclic deformation Pritam Kumar Jana,1,2,* Mikko J. Alava,1 and Stefano Zapperi1,3,4 1COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Espoo, Finland 2Université Libre de Bruxelles (ULB), Interdisciplinary Center for Nonlinear Phenomena and Complex Systems, Campus Plaine, CP 231, Blvd. du Triomphe, B-1050 Brussels, Belgium 3Center for Complexity and Biosystems, Department of Physics, University of Milano, via Celoria 16, 20133 Milano, Italy 4CNR-ICMATE, Via R. Cozzi 53, 20125, Milano, Italy (Received 26 June 2018; published 14 December 2018) Cyclic loading on granular packings and amorphous media leads to a transition from reversible elastic behavior to an irreversible plasticity. In the present study, we investigate the effect of oscillatory shear on polycrystalline and amorphous colloidal solids by performing molecular dynamics simulations. Our results show that close to the transition, both systems exhibit enhanced particle mobility, hysteresis, and rheological loss of rigidity. However, the rheological response shows a sharper transition in the case of the polycrystalline sample as compared to the amorphous solid. In the polycrystalline system, we see the disappearance of disclinations, which leads to the formation of a monocrystalline system, whereas the amorphous system hardly shows any ordering. After the threshold strain amplitude, as we increase the strain amplitude both systems get fluid. In addition to that, particle displacements are more homogeneous in the case of polycrystalline systems as compared to the amorphous solid, mainly when the strain amplitude is larger than the threshold value.
    [Show full text]
  • Evidence for a Superglass State in Solid 4He
    Evidence for a Superglass State in Solid 4He B. Hunt,1§ E. Pratt,1§ V. Gadagkar,1 M. Yamashita,1,2 A. V. Balatsky3 and J.C. Davis1,4 1 Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA. 2 Department of Physics, Kyoto University, Kyoto 606-8502, Japan. 3 T-Division, Center for Integrated Nanotechnologies, MS B 262, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. 4 Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, Scotland, UK. §These authors contributed equally to this work. Science 324, 632 (1 May 2009) Although solid helium-4 (4He) may be a supersolid it also exhibits many phenomena unexpected in that context. We studied relaxation dynamics in the resonance frequency f(T) and dissipation D(T) of a torsional oscillator containing solid 4He. With the appearance of the “supersolid” state, the relaxation times within f(T) and D(T) began to increase rapidly together. More importantly, the relaxation processes in both D(T) and a component of f(T) exhibited a complex synchronized ultra-slow evolution towards equilibrium. Analysis using a generalized rotational susceptibility revealed that, while exhibiting these apparently glassy dynamics, the phenomena were quantitatively inconsistent with a simple excitation freeze-out transition because the variation in f was far too large. One possibility is that amorphous solid 4He represents a new form of supersolid in which dynamical excitations within the solid control the superfluid phase stiffness. A ‘classic’ supersolid (1-5) is a bosonic crystal with an interpenetrating superfluid component.
    [Show full text]
  • SOLID STATE PHYSICS PART II Optical Properties of Solids
    SOLID STATE PHYSICS PART II Optical Properties of Solids M. S. Dresselhaus 1 Contents 1 Review of Fundamental Relations for Optical Phenomena 1 1.1 Introductory Remarks on Optical Probes . 1 1.2 The Complex dielectric function and the complex optical conductivity . 2 1.3 Relation of Complex Dielectric Function to Observables . 4 1.4 Units for Frequency Measurements . 7 2 Drude Theory{Free Carrier Contribution to the Optical Properties 8 2.1 The Free Carrier Contribution . 8 2.2 Low Frequency Response: !¿ 1 . 10 ¿ 2.3 High Frequency Response; !¿ 1 . 11 À 2.4 The Plasma Frequency . 11 3 Interband Transitions 15 3.1 The Interband Transition Process . 15 3.1.1 Insulators . 19 3.1.2 Semiconductors . 19 3.1.3 Metals . 19 3.2 Form of the Hamiltonian in an Electromagnetic Field . 20 3.3 Relation between Momentum Matrix Elements and the E®ective Mass . 21 3.4 Spin-Orbit Interaction in Solids . 23 4 The Joint Density of States and Critical Points 27 4.1 The Joint Density of States . 27 4.2 Critical Points . 30 5 Absorption of Light in Solids 36 5.1 The Absorption Coe±cient . 36 5.2 Free Carrier Absorption in Semiconductors . 37 5.3 Free Carrier Absorption in Metals . 38 5.4 Direct Interband Transitions . 41 5.4.1 Temperature Dependence of Eg . 46 5.4.2 Dependence of Absorption Edge on Fermi Energy . 46 5.4.3 Dependence of Absorption Edge on Applied Electric Field . 47 5.5 Conservation of Crystal Momentum in Direct Optical Transitions . 47 5.6 Indirect Interband Transitions .
    [Show full text]
  • Constructing a Theory for Amorphous Solids
    VIEWPOINT Constructing a Theory for Amorphous Solids Theorists are coming closer to a comprehensive description of the mechanics of solids with an amorphous structure, such as glass, cement, and compacted sand. by Emanuela Del Gado∗ general field theory for amorphous solids and uses it to pre- dict how they transmit stress. morphous solids are disordered assemblies of Researchers are already equipped with equations that pre- atoms or larger particles that nonetheless have a dict the mechanical response of a perfectly crystalline solid rigid structure. Examples include glass, cement, from its atomic structure [3]. These equations can, for ex- compacted sand, and even yogurt or chocolate ample, describe how a piece of such a solid would deform Amousse (Fig. 1). At first sight, these materials may appear under a load. But it has proven much harder to find an anal- to have little in common. But amorphous solids share many ogous set of equations for amorphous solids. The biggest mechanical properties, and physicists have long been inter- barrier to developing such a theory is that, even in the ab- ested in finding a theory that predicts the materials’ behavior sence of a load, an amorphous solid always has internal in terms of their microstructure in a unified way. Unlike stresses, which build up within the material as it solidifies crystalline solids, however, the rigidity of amorphous solids [4]. For example, when sand compacts, internal stresses de- is not associated with a thermodynamically stable, stress- velop from friction between the grains and from constraints free microstructure, so researchers have had to turn to novel imposed by the material’s outer boundary.
    [Show full text]
  • Mixing Periodic Topographies and Structural Patterns on Silicon Surfaces Mediated by Ultrafast Photoexcited Charge Carriers
    PHYSICAL REVIEW RESEARCH 2, 043080 (2020) Mixing periodic topographies and structural patterns on silicon surfaces mediated by ultrafast photoexcited charge carriers Jean-Philippe Colombier ,1,* Anton Rudenko ,1 Elena Silaeva ,1 Hao Zhang,1 Xxx Sedao ,1 Emile Bévillon,1 Stéphanie Reynaud,1 Claire Maurice,2 Florent Pigeon,1 Florence Garrelie,1 and Razvan Stoian1 1Univ Lyon, UJM-St-Etienne, CNRS, Institute of Optics Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023 Saint-Etienne, France 2Ecole Nationale Supérieure des Mines de Saint-Etienne, Laboratoire Georges Friedel, CNRS, UMR5307, 42023 St-Etienne, France (Received 12 June 2020; revised 15 September 2020; accepted 22 September 2020; published 15 October 2020) Ultrafast laser irradiation of silicon can significantly modify charge densities and optical indices, impacting the formation and the development of nanoscale-arranged periodic structures. Photoexcitation degree as well as thermodynamic, hydrodynamic, and structural aspects are reported for crossed orientation of laser-induced periodic surface structures generated on single-crystal silicon after multiple-pulse femtosecond laser irradi- ation. The periodic topography and microstructure generated by light scattering on surface nanoroughness were characterized to gain insights into the regime of photoexcitation, subsequent thermodynamic conditions, and inhomogeneous energy deposition related to periodic nanostructure formation and growth. A generated free-carrier density around (3 ± 2) × 1021 cm−3 is estimated from time-resolved ellipsometry and supported by time-dependent density-functional theory calculations. A finite-difference time-domain solution of the far-field interference of the surface scattered light and the refracted laser wave confirms the periodically crossed energy deposition for this excitation degree. The interference process does not necessarily involve surface plasmon polaritons, and quasicylindrical evanescent waves are identified as plausible scattered waves requiring less restrictive conditions of photoexcitation.
    [Show full text]
  • A Non-Volatile Chalcogenide Switchable Hyperbolic Metamaterial
    DOI: 10.1002/ ((please add manuscript number)) Article type: Communication A non-volatile chalcogenide switchable hyperbolic metamaterial Harish N. S. Krishnamoorthy, Behrad Gholipour, Nikolay I. Zheludev, and Cesare Soci* Dr. Harish N. S. Krishnamoorthy, Prof. Nikolay I. Zheludev, Prof. Cesare Soci Centre for Disruptive Photonic Technologies, TPI, SPMS, Nanyang Technological University, Singapore 637371 Email: [email protected] Dr. Behrad Gholipour, Prof. Nikolay I. Zheludev Optoelectronics Research Centre & Centre for Photonic Metamaterials, University of Southampton, SO17 1BJ, Southampton, UK Keywords: phase change, non-volatile, chalcogenide, hyperbolic, metamaterial Abstract: Phase change materials have enabled the realization of dynamic nanophotonic devices with various functionalities. Reconfigurable hyperbolic metamaterials integrated with such elements have been demonstrated in the past but the volatile nature of their optical properties has been a limitation, particularly for applications that require the device to be preserved in a specified state. Here, we report the first proof-of-concept demonstration of a non-volatile, switchable hyperbolic metamaterial based on a chalcogenide glass. By using the Ge2Sb2Te5 (GST) alloy as one of the components of a multilayered nanocomposite structure and exploiting its phase change property, we demonstrate a hyperbolic metamaterial in which the type-I hyperbolic dispersion (훆⊥ < ퟎ, 훆∥ > ퟎ) and negative refraction can be switched from the near-infrared to the visible region. This opens up
    [Show full text]
  • Crystallography Overview for Microsystems
    CRYSTALLOGRAPHY OVERVIEW FOR MICROSYSTEMS Crystal Silicon Planes Crystallography Learning Module Unit Overview This unit reviews the science of crystallography as it relates to the construction of microsystem (MEMS) components. Three types of solids (amorphous, polycrystalline, and crystalline) are covered as well as how to identify crystal orientation based on Miller indices. Objectives v State at least one example for each type of solid matter (amorphous, polycrystalline and crystalline). v Discuss the importance of crystal structures in MEMS fabrication. v Identify the direction of a crystal plane using the Miller index notation. Introduction v Crystallography is the science of determining the arrangement of atoms in solid matter. v Irregular arrangements are called amorphous or noncrystalline. v Definitive patterns with a repeating structure are called crystalline structures. v All solid matter is either amorphous, crystalline or polycrystalline. Which of these solids is the crystalline solid? Introduction v Crystallography is the science of determining the arrangement of atoms in solid matter. v Irregular arrangements are called amorphous or noncrystalline. v Definitive patterns with a repeating structure are called crystalline structures. v All solid matter is either amorphous, crystalline or polycrystalline. Which of these solids is the crystalline solid? Pretty easy to tell, isn’t it? The lower left is cut glass. The right is a high quality diamond. What are you familiar with? v What are some examples of amorphous solid? v What are some examples of crystalline solids? What are you familiar with? v What are some v glass, soot, plastics, gels examples of amorphous solid? v What are some v diamonds, ice, quartz, examples of crystalline and an old favorite, rock solids? candy Crystals and MEMS Because the atoms or molecules of crystalline structures "fit together" so well, a crystal is typically very strong – an important characteristic in the construction of micro and nano- sized devices.
    [Show full text]
  • Amorphous Solid Dispersions-One Approach to Improving Bioavailability
    2017 WHITE PAPER: Amorphous Solid Dispersions-One approach to improving Bioavailability Eric C Buxton Clinical Associate Professor University of Wisconsin Madison School of Pharmacy, Division of Pharmacy Professional Development Page | 1 Amorphous Solid Dispersions‐One approach to improving Bioavailability Though amorphous solid dispersions can add complexity to a drug development project, the difference they make can be the difference between bioavailable drug and failed project. During product development, the formulator’s first task is to understand the properties of the API they are working with. This includes not just an understanding of the basic physicochemical properties, but the biopharmaceutical properties of the candidate as well. For BCS II drug candidates, a common product development approach is to utilize manufacturing processes that generate amorphous solid dispersions with a high degree of prolonged supersaturation. The choice of excipients for these formulations is A promising drug development project can be critical not just to achieve slowed or halted if the candidate compound has drug delivery goals poor aqueous solubility and dissolution (bioavailability), but the characteristics. excipients selected also need to be compatible with the selected manufacturing process. The excipients used and the specific formulation compositions selected also directly impact the stability of the disordered system and impact the packaging selection and dictate the environmental controls/handling requirements of the final product. Many small molecules cannot be crystallized in forms that are stable and suitable for formulation. Crystalline solids can be inadvertently rendered partially amorphous by processing (e.g. milling and drying) leading to instabilities. In addition, many crystalline APIs lack sufficient aqueous solubility to provide adequate oral bioavailability whereas the amorphous form can enhance dissolution characteristics.
    [Show full text]
  • Colloid Based Crystalline and Amorphous Structures
    Colloid based crystalline and amorphous structures Markus Bier Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584CE Utrecht, The Netherlands E-mail: [email protected] Abstract. These notes are intended to summarise the content of a talk given by the author at the conference "From Physical Understanding to Novel Architectures of Fuel Cells" (21{25 May 2007, Trieste, Italy). A few basic concepts of colloidal science and the simple DLVO theory are introduced in order to provide the reader with a crude understanding of colloidal interactions. Without going into numerical details, this insight leads directly to a generic phase diagram of colloids in terms of which processes of structure formation can be illustrated. A few real examples of synthesised colloid based crystalline and amorphous structures will be shown in the presentation. The highlight will be a recently fabricated porous amorphous structure designed for the application in fuel cell electrodes. It is the authors intention not to give detailed explanations on recent improvements in colloidal science but to qualitatively illustrate how principles of colloidal science can be applied in the development of, e.g., novel fuel cell architectures. Colloid based crystalline and amorphous structures 2 1. Definition of terms Colloid science [1] as a discipline of chemistry, to which also physicists, geologists, and agronomists contributed, exists for more than a century now. Hence it is understandable that definitions within colloidal science have been changing with time and that there is not always common agreement upon terms. Here some basic definitions are given as they will be used in the following; however, the reader should not assume that other colloid scientists use the same definitions.
    [Show full text]