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) compo‐ 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 dif‐ 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 pat‐ 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 tis‐ 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 mus‐ 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 align‐ 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 pecu‐ liar matrix alignment relative to the muscle axis. It gives a substantial resistance and excep‐ 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 physiolog‐ 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 ei‐ ther by birefringence measurements [24, 25], mechanical testing in different axis [26], immu‐ 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, electro‐ 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