Thamarasee Jeewandara | University of California, San Francisco (original) (raw)

Papers by Thamarasee Jeewandara

Topography and characterization of proximitized Bi2Te3 thin films. (A) Quasiparticle dispersion a... more Topography and characterization of proximitized Bi2Te3 thin films. (A) Quasiparticle dispersion around the superconducting gap without magnetic field (blue curve) and with magnetic field above B* (red curve) that induces gapless superconducting state (for parabolic dispersion B* ~ ?/ev?L, with e the electron charge, and v the Fermi velocity). (B) Schematic depiction of a segmented Fermi surface that arises owing to magnetic field B along x axis. Solid red lines indicate electrondominated states, whereas dashed red lines show holedominated states. The pink line indicates the Fermi surface of the normal state. (C) Structure of the samples with few quintuple layers of Bi2Te3 on top of NbSe2. An external in-plane magnetic field Bext induces perpendicular screening supercurrent and Cooper pair momentum q. Insets show the topography of a large area (320 × 320 nm2) of the thin film with regions of varying thickness and an atomic resolution image (10 × 10 nm2) of Bi2Te3 lattice. White recta...

Sheet resistances of the NBCO and YBCO films as a function of the temperature. The sheet resistan... more Sheet resistances of the NBCO and YBCO films as a function of the temperature. The sheet resistance R? is plotted as a function of the temperature for (A) sample UD60b (thickness: 100 nm; deposited in the same conditions as sample UD60); (B) sample UD81 (thickness: 50 nm); (C) sample OP90 (thickness: 100 nm); (D) sample OD83 (thickness: 50 nm). The critical temperature Tc of the films has been extracted from the maximum of the first derivative of the R(T) characteristic (inset in the four panels). The pseudogap temperature T* is instead inferred by the departure from the linear R(T) behavior at high temperature, which is a signature of the strange metal phase of cuprates (dashed line in the four panels). For the sample OD83, the temperature T* is not defined. Indeed, the sample is slightly overdoped, as highlighted by the curvature of the R(T) characteristic at lower temperature, which is opposite with respect to that characterizing the underdoped films. In this doping range, the te...

Characterization of Au-Cu2O catalyst and its catalytic performance response to illumination. (A) ... more Characterization of Au-Cu2O catalyst and its catalytic performance response to illumination. (A) Schematic of the SP-regulated partial oxidation of propylene on the AuCu2O plasmonic structure. (B) SEM image of the asprepared Au-Cu2O hierarchical structure. (C) XRD patterns of the as-prepared C-Cu2O and Au-Cu2O hierarchical structure. a.u., arbitrary unit. (D) XPS of Cu of the as-prepared C-Cu2O and Au-Cu2O hierarchical structure. (E) Conversion and selectivity of the partial propylene oxidation for Au-Cu2O at 150°C with and without illumination, showing the improvement in conversion induced by light and the influence on product selectivity. (F) Conversion of propylene for Cu2O and AuCu2O with and without illumination at various temperatures. (G) Conversion enhancements induced by illumination for Cu2O and Au-Cu2O as a function of the operating temperature. (H) Selectivity of acrolein catalyzed by Cu2O (gray) and Au-Cu2O (red) with and without illumination as a function of propylene ...

Schematic illustration of regulating the reactivity of BP via protective chemistry. Protective st... more Schematic illustration of regulating the reactivity of BP via protective chemistry. Protective step 1: Binding Al3+ ions with lone pair electrons on the surface of P atoms decreases surface electron density of BP, leading to a reduced chemical reactivity of BP. Protective step 2: Selfassembly of the hydrophobic dense array on the BP surface isolates BP from surrounding oxygen/water. Deprotective step: Removal of Al3+ ions and hydrophobic dense array on the BP surface by a chelating agent. The treatment recovers the electron density of BP, restoring the original reactivity of the deprotected BP. BDT, 1,2-benzenedithiol; EDTA-4Na, EDTA-tetrasodium. Credit: Science Advances, doi: 10.1126/sciadv.abb4359.

LEFT: Schematic of optical setup for optical reconstruction of holographic scenes at various obse... more LEFT: Schematic of optical setup for optical reconstruction of holographic scenes at various observation angles. Cage system parts are omitted for schematic clarity but serve to keep the collimating condition of the light incident on the metasurface constant for varying swivel angles, ?. RIGHT: Two degrees of freedom enable independent and complete control of the optical amplitude and phase. (a) Schematic of the holographic experiment: circularly polarized light is partially converted by the metasurface to its opposite handedness and is then filtered by an analyzing polarization filter before forming an image on the camera. (b) Geometrical parameters of the metaatoms sweep the amplitude (black-white gradient axis) and phase (rainbow axis) of the output signal. (c) The meta-atoms in (b) can take incident left circularly polarized light (south pole) to any other point on the Poincaré sphere with near-unity efficiency representing two independent degrees of freedom controlled by the me...

Charge dynamics of the chiral anomaly in a DSM and the experimental setup. (A) Schematic illustra... more Charge dynamics of the chiral anomaly in a DSM and the experimental setup. (A) Schematic illustration of the low-energy electronic structure of the DSM Cd3As2. It hosts two 3D Dirac nodes located along the kz axis. (B) The chiral anomaly is expected when the dc magnetic field and the THz electric field are coaligned. (C) Schematic of the time domain magnetoterahertz spectrometer used to collect data. Wire grid polarizer 1 (WGP1) and WGP2 are used to produce linearly polarized terahertz pulse with ETHz ? B or ETHz ? B. A fast rotation polarizer (FRP) is used to modulate terahertz electric field by a frequency near 47 Hz. With WGP3 and lock-in amplifier, the complex transmission matrix can be determined through a single measurement to high precision. (D) In a DSM with ETHz ? B, the 3D Dirac states will develop Landau levels (LLs), which are dispersive along the direction of magnetic field. The zeroth LL gives the chiral current. A number of different relaxation rates control the charg...

Illustration of the MagneTEskin process. (1) A magnetic coating (black layer) is applied to the e... more Illustration of the MagneTEskin process. (1) A magnetic coating (black layer) is applied to the epidermal surface of the donor site before harvest. (2) The harvested MSTCs are submerged in either a biomaterial solution (for the biomaterial embedding option) or sterile saline (for the topical binding option). (3) An external magnetic field is applied to induce the MSTCs to align in the same orientation and gather closely together. (4) To increase the packing density and attachment between individual MSTCs (if so desired), excess fluid could be removed by gentle dabbing with an absorbent material and letting the construct air dry. (5) The external magnetic field is removed. (6) For the biomaterial embedding option, the liquid biomaterial is induced to solidify and cross-linked to increase mechanical strength. (7) For the topical binding option, either an adhesive film dressing or a cyanoacrylate surgical glue is applied to the top surface of the assembled MSTCs. (8) The constructs are...

Schematic illustration of the design of an integrated nanozyme with cascade anti-ROS activity for... more Schematic illustration of the design of an integrated nanozyme with cascade anti-ROS activity for IBD therapy. (A) Cellular cascade enzymes for anti-ROS. The therapeutic efficacy of such a system is limited because of the different subcellular locations of SOD and CAT enzymes and limited extracellular stability. (B) Constructing a cascade nanozyme for anti-ROS therapy by embedding Pt NPs inside PCN222-Mn MOF. Nanoscale proximity of catalytic active sites promotes the cascade reactions. (C) The IBD of mice can be effectively relieved through treatment with the integrated cascade nanozyme. Credit: Science Advances, doi: 10.1126/sciadv.abb2695

Design and characterizations of strain-sensitive, stretchable, and self-healable semiconducting f... more Design and characterizations of strain-sensitive, stretchable, and self-healable semiconducting film. (A) Chemical structure of DPP semiconducting polymer, PDMS, and PDCA moiety introduced in both polymer backbones as dynamic bonding sites through metalligand interaction. Structure of the [Fe(HPDCA)2]+ moiety that is reversible dynamic bonds by force. (B) Schematic illustration of DPP and PDMS dynamically cross-linked through Fe(III)-PDCA complexation. (C) STEM dark-field and STEM-EDS elemental mapping of the DPP-TVT-PDCA (1): PDMS-PDCA-Fe (5) blend film. (D) Field-effect mobilities of the blend film organic thinfilm transistors (OTFTs) (source and drain electrode: Au, 40 mn; dielectric layer: SiO2, 300 nm; gate electrode: highly doped silicon substrate) as a function of blendingweight ratio (semiconductor: elastomer). (E) Strain cyclic testing of the blend film (1:5). (F) Plot of dichroic ratio (??/??) of 1:5 blend film as a function of strain. (G) Relative degree of crystallinity ...

Device geometry and magneto-transport data. (A) Schematic diagram of device geometry. (B) Schemat... more Device geometry and magneto-transport data. (A) Schematic diagram of device geometry. (B) Schematic diagram of moiré superlattice formed by the twisted graphene layers. (C) Rxx versus magnetic field B and gate voltage Vg showing a Landau fan pattern. The top axis labels nm, the number of charges per superlattice cell. (D). Rxx(Vg) at different temperatures. Inset: Optical image of a tBLG device with a scale bar of 10 ?m. Credit: Science Advances, doi: 10.1126/sciadv.aaw9770

Design concept of the water lily–inspired hierarchical structure. (A and B) Water lily and water ... more Design concept of the water lily–inspired hierarchical structure. (A and B) Water lily and water lily–inspired design for solar vapor generation, respectively. They share several key features: the upper epidermis with hydrophobic surface absorbs the sunlight and provides stomata for water vapor escape, lacunae (air chamber) at the bottom of the leaf keep a water lily afloat on the water, and vascular bundles (water path) provide a confined water supply. (C) Microscale schematic of a confined water layer sandwiched between the hydrophobic top solar absorber and the bottom stand with low thermal conductivity. Evaporation occurs at the water surface below the absorber, and salt/solute is excreted by the water path, avoiding accumulation/crystallization of solute on the absorber. (D) Nanoscale light trapping for the top solar absorber. (E) Molecular-scale surface modification for the hydrophobic surface of the top solar absorber. Credit: Science Advances, doi: 10.1126/sciadv.aaw7013

Schematic diagram of the electrically assisted 3Dprinting platform for the construction of nacre-... more Schematic diagram of the electrically assisted 3Dprinting platform for the construction of nacre-inspired structures. (A) Diagram of the electrically assisted 3Dprinting device. (B) Illustration of the bottom-up projection-based stereolithography process. (C and D) Schematic diagrams show the alignment of GNs under the electric field and alignment mechanisms, respectively. (E) 3D-printed nacre with aGNs and SEM images showing surface and cross-section morphology: DMD, digital micromirror device; PDMS, polydimethylsiloxane. Credit: Science Advances, doi: 10.1126/sciadv.aau9490

Materials such as poly(?-caprolactone) are used as scaffolds in bone tissue engineering, but thei... more Materials such as poly(?-caprolactone) are used as scaffolds in bone tissue engineering, but their inherent hydrophobicity and surface smoothness can impair cell attachment, proliferation and differentiation in the lab, or after implantation in vivo. Surface modifications including chemical alterations or the immobilization of biologically active molecules on materials can overcome the intrinsic hydrophobicity of poly(?-caprolactone) (PCL). In a recent study, bioengineers Yasaman Zamani and her colleagues investigated a chemically modified, 3-D printed PCL material surface immobilized with RGD peptide (R: arginine, G: glycine, D: aspartic acid). The results of the study are published on Biomedical Materials, IOP Publishing.

Living organisms form biological minerals during biomineralization, where inorganic elements can ... more Living organisms form biological minerals during biomineralization, where inorganic elements can selectively deposit on specific organic macromolecules under precise control. The process can be divided into biocalcification or biosilicification based on the inorganic component, with collagen used as a universal template. During intrafibrillar mineralization, collagen matrices that are destined for mineralization in vertebrates contain surface bound matrix proteins. Understanding the complex mechanisms of intrafibrillar mineralization to form hard collagenous tissue such as bone and dentin is of significant interest in biomechanics, with decades of studies conducted to mimic or model the process in lab. In a recent study, now published in Science Advances, Q. Song and co-workers at the interdisciplinary Departments of Biology, Applied Physics, Materials Science and Engineering, Biomedical Sciences and Dental Medicine, in China, the U.S. and Italy, have developed a biomechanical model...

3D thermoelectric coils as active components of flexible and deformable systems to harvest electr... more 3D thermoelectric coils as active components of flexible and deformable systems to harvest electric power for wearable technologies. A) Schematic illustration of fabrication and 3D assembly. Thin-film pand n-type materials were patterned into 2D serpentine shapes and transferred onto a layer of polyimide (PI) to form the active materials. The 2D precursor structures were completed with metal junctions and a surface coating of PI patterned via photolithography and etching. Chemical bonding such systems to pre-structured silicone substrates at selective locations were followed by prestretch to initiate a process of geometrical transformations to yield the final 3D architecture. B) Optical images of resulting 3D thermoelectric coils. The geometry of the structure and elastomer substrate combined to provide mechanical robustness against handling and mechanical deformation. C) An array of 8 x 8 coils. The magnified view shows the 3D structure is consistent to the geometry predicted by FE...

Illustration of the multifunctional materials experimentally developed in the study for in vivo a... more Illustration of the multifunctional materials experimentally developed in the study for in vivo applications of cell proliferation and cranioplasty. Defect healing in a rodent model is observed after 12 weeks of scaffold implantation at the site of defect with cell proliferation, radiography, micro-CT and histology analyses. Image credit: ACS Applied Materials & Interfaces. Credit: Multifunctional Materials, doi: https://doi.org/10.1088/2399-7532/aafc5b

Clinical and experimental pharmacology & physiology, 2015

Studies were performed to examine the contribution of aldosterone to the pathogenesis of cardiova... more Studies were performed to examine the contribution of aldosterone to the pathogenesis of cardiovascular and renal disease in a rodent model of genetic kidney disease. Spironolactone (20 mg/kg per day) was administered in water to mixed sex Lewis Polycystic Kidney (LPK) rats (n = 20) and control Lewis rats (n = 27) from 4 to 12 weeks of age. At 12 weeks of age, hypertension was reduced in female LPK rats; systolic blood pressure declined from 226.4 ± 26.8 mmHg in untreated rats and to 179.2 ± 3.2 mmHg in treated rats (P = 0.018). No similar effect on male or control rats was found. Water consumption and urine volume were significantly greater in LPK animals than in Lewis rats, and treatment reduced both variables by ~30% in LPK animals (P < 0.05). Proteinuria and the urinary protein-to-creatinine ratio were normalized in treated LPK relative to Lewis controls, and plasma creatinine levels were significantly reduced by treatment in LPK rats. Spironolactone did not alter kidney morp...

Cobalt Chromium alloy L605 is an underlying biomaterial for most new generation drug eluting sten... more Cobalt Chromium alloy L605 is an underlying biomaterial for most new generation drug eluting stents (DES) and bare metal stents
(BMS). Suboptimal biocompatibility of stents clinically manifest as thrombosis and restenosis. We optimized a plasma-activated
coating (PAC) technology to modify alloy L605 material surface (PAC-L605), for the first time, for enhanced biocompatibility. This
study details in vitro characterization to identify and optimize the physical, chemical, and mechanical properties of the modified
material surface PAC-L605. Surface hydrophilicity characterized post-modification with water contact angle and plasma kinetics,
showed improved hydrophilicity for PAC-L605. Surface chemistry of PAC-L605 vs. L605, quantified with energy dispersive x-ray
spectroscopy (EDS), showed comparatively higher weight percent of carbon and nitrogen on PAC surfaces. The microscale,
isotropic surface roughness of PAC-L605, was computed with NanoMap white light interferometry (WLI). Surface stiffness computed
via nanoindentation at minimum compression load 0.19 mN - increasing to maximum load 50 mN, showed similar stiffness for PACL605
and L605 at higher load. Nanoindentation results confirmed robust adhesion of PAC to L605, and unique non-delaminating
character of PAC under compression. Furthermore, surface modification at PAC-L605 interface was visualized via high-resolution
transmission electron microscopy (HRTEM). Improvements of surface character for implantable cardiovascular materials could be
achieved by plasma-activated coating (PAC). Optimal surface modifications may trigger desirable biological responses in vitro and in
vivo

Clinical and experimental pharmacology & physiology, 2015

Doctoral Thesis : The Sydney eScholarship Repository Issued on the 30th September 2015