87 research outputs found
Growth, Structure and Properties of Epitaxial Thin Films of First Principles Predicted Multiferroic Bi2FeCrO6
We report the structural and physical properties of epitaxial Bi2FeCrO6 thin
films on epitaxial SrRuO3 grown on (100)-oriented SrTiO3 substrates by pulsed
laser ablation. The 300 nm thick films exhibit both ferroelectricity and
magnetism at room temperature with a maximum dielectric polarization of 2.8
microC/cm2 at Emax = 82 kV/cm and a saturated magnetization of 20 emu/cc
(corresponding to ~ 0.26 Bohr magneton per rhombohedral unit cell), with
coercive fields below 100 Oe. Our results confirm the predictions made using
ab-initio calculations about the existence of multiferroic properties in
Bi2FeCrO6.Comment: Manuscript accepted for publication in Applied Physics Letters (in
press). The paper consists of 1619 words, 13 references and 3 figure
Magnetically controlled dielectrophoresis of metallic colloids
Peer reviewed: YesNRC publication: Ye
Alignment of Cells and Extracellular Matrix Within Tissue- Engineered Substitutes
Most of the cells in our body are in direct contact with extracellular matrix (ECM) compoâ
nents which constitute a complex network of nano-scale proteins and glycosaminoglycans.
Those cells constantly remodel the ECM by different processes. They build it by secreting difâ
ferent proteins such as collagen, proteoglycans, laminins or degrade it by producing factors
such as matrix metalloproteinase (MMP). Cells interact with the ECM via specific receptors,
the integrins [1]. They also organize this matrix, guided by different stimuli, to generate patâ
terns, essential for tissue and organ functions. Reciprocally, cells are guided by the ECM, they
modify their morphology and phenotype depending on the protein types and organization
via bidirectional integrin signaling [2-4]. In the growing field of tissue engineering [5], control
of these aspects are of the utmost importance to create constructs that closely mimic native tisâ
sues. To do so, we must take into account the composition of the scaffold (synthetic, natural,
biodegradable or not), its organization and the dimension of the structure.
The particular alignment patterns of ECM and cells observed in tissues and organs such as
the corneal stroma, vascular smooth muscle cells (SMCs), tendons, bones and skeletal musâ
cles are crucial for organ function. SMCs express contraction proteins such as alpha-smoothmuscle
(SM)-actin, desmin and myosin [6] that are essential for cell contraction [6]. To result
in vessel contraction, the cells and ECM need to be organized in such a way that most cells
are elongated in the same axis. For tubular vascular constructs, it is suitable that SMCs align
in the circumferential direction, as they do in vivo [7, 8]. Another striking example of alignâ
ment is skeletal muscle cells that form long polynuclear cells, all elongated in the same axis.
Each cell generates a weak and short contraction pulse but collectively, it results in a strong,
long and sustained contraction of the muscle and, in term, a displacement of the member. In the corneal stroma, the particular arrangement of the corneal fibroblasts (keratocytes) and
ECM is essential to keep the transparency of this tissue [9-13]. Tendons also present a pecuâ
liar matrix alignment relative to the muscle axis. It gives a substantial resistance and excepâ
tional mechanical properties to the tissue in that axis [14, 15]. Intervertebral discs [16],
cartilage [17], dental enamel [18], and basement membrane of epithelium are other examples
of tissues/organs that present peculiar cell and matrix organization. By reproducing and
controlling those alignment patterns within tissue-engineered substitutes, a more physiologâ
ical representation of human tissues could be achieved.
Taking into account the importance of cell microenvironment on the functionality of tissue engineered
organ substitutes, one can assume the importance of being able to customise the
3D structure of the biomaterial or scaffold supporting cell growth. To do so, some methods
have been developed and most of them rely on topographic or contact guidance. This is the
phenomenon by which cells elongate and migrate in the same axis as the ECM. Topographic
guidance was so termed by Curtis and Clark [19] to include cell shape, orientation and
movement in the concept of contact guidance described by Harrison [20] and implemented
by Weiss [21, 22]. Therefore, if one can achieve ECM alignment, cells will follow the same
pattern. Inversely, if cells are aligned on a patterned culture plate, the end result would be
aligned ECM deposition [23].
The specific property of tissues or materials that present a variation in their mechanical and
structural properties in different axis is called anisotropy. This property can be evaluated eiâ
ther by birefringence measurements [24, 25], mechanical testing in different axis [26], immuâ
nological staining of collagen or actin filaments [23] or direct visualisation of collagen fibrils
using their self-fluorescence around 488 nm [27, 28].
Several techniques have been recently developed to mimic the specific alignment of cells
within tissues to produce more physiologically relevant constructs. In this chapter, we will
describe five different techniques, collagen gel compaction, electromagnetic field, electroâ
spinning of nanofibers, mechanical stimulation and microstructured culture plates
Improving the reliability and complexity of advanced electrowetting-based digital microfluidic devices
Peer reviewed: YesNRC publication: Ye
Patterning of chemical gradients with submicrometer resolution using edge-spreading lithography
Peer reviewed: YesNRC publication: Ye
Micro- and Nanoscale Patterning of Alkanethiol Monolayers on Gold using Edge-Spreading Lithography
Peer reviewed: NoNRC publication: Ye
Chemical force microscopy for hot-embossing lithography release layer characterization
We employed variable temperature chemical force microscopy (VT-CFM) using tips silanized with four different hydro- and hydrofluoroalkyl self-assembling monolayers (SAMs) interacting with a thin-film of poly(cyclic olefin), (PCO) to model the hot-embossing stamp-polymer interaction over a temperature range spanning the glass transition of the PCO.Peer reviewed: YesNRC publication: Ye
Water-oil core-shell droplets for electrowetting-based digital microfluidic devices
Peer reviewed: YesNRC publication: Ye
High fidelity, high yield production of microfluidic devices by hot embossing lithography : Rheology and stiction
We discuss thermoforming of thermoplastic polymers for the hot-embossing lithographic (HEL) fabrication of microfluidic chips near equilibrium conditions that minimize elastic recoil for optimal motif replication. While HEL is often simplistically described as the transfer of micro- and nano-motifs into heat-softened thermoplastic materials, we describe our rational approach to selecting appropriate processing parameters.Peer reviewed: YesNRC publication: Ye
- âŠ