Solvothermally treating an as-prepared poly(vinylidenefluoride) (PVDF) colloidal suspension leads to a significant impact on the surface properties of the resulting topcoat on a pertinent prime coating. The coating, possessing a fibrous porous matrix, exhibits a water contact angle in the range of 115–136°. However, the coating possesses droplets sticking ability that can be attributed to the pseudo-hydrogen bonding effect of the polarized C–H bonds in each repeating unit of PVDF polymer chains. The hydrophobicity of the topcoat is affected by the formulation of colloidal suspension, which is carried out by introducing a solution of PVDF in dimethylforamide into an excess of methanol. The colloidal suspension formed is subjected to solvothermal treatment subsequently. By thermodynamics, the treatment enhances chain packing density and growth of crystallites inside the colloidal particles of PVDF in the methanol-dominant dispersion medium. Furthermore, the realized chain packing states are retained during the drying of coating through chain affixation role of a small number of poly(divinylbenzene) nodules generated in situ. As a result, a fibrous porous matrix composed of the PVDF submicron knots is attained. The coexistence of the polarized CH2 group and the fibrous porous structure prompts a sticky hydrophobic surface. 相似文献
A systematic investigation into the influence of the degree of fluorination on the static and dynamic wetting behavior of TiO2‐based nanobelt (TNB) particles with various liquids is described. The effect of the degree of fluorination and the surface tension of the liquid on the occurrence and stability of liquid marbles, foams or dispersions are studied and the wetting behavior and arrangement of particles at the air–liquid surface are observed. Using contact angle (θ) measurements, the relation between the type of particle‐stabilized material and θ is established. For liquids of relatively high tension like water or formamide which do not wet the fluorinated particles, a powder‐like material (marble) is formed. For polar oils of intermediate tension (35–50 mN m?1), which partially wet the fluorinated particles, stable air‐in‐oil foams can be prepared in which particles form a close‐packed layer enveloping air bubbles. Liquids of relatively low tension, e.g., ethanol or polydimethylsiloxane, wet the particles forming a uniform dispersion and partial sedimentation. By contrast, the as‐prepared hydrophilic TNB particles are rapidly wetted by all the liquids as expected due to their high surface energy. The stable cross‐stacked TNB particles with fluoroalkylsilane (FAS) modification could be a versatile platform in a wide range of applications, especially for fluidic devices (e.g., biofluids, gas sensing, and lab‐on‐a‐chip devices). In a proof‐of‐concept study, the oil–water separation performance of fabrics with chemically stable TNB/FAS coating and the liquid isolation by a TNB/FAS shell for highly sensitive gas sensing or reagent assays are investigated. 相似文献
Human mesenchymal stem cells (MSCs) derived from various origins show varied differentiation capability. Recent work shows that cell shape manipulation via micropatterning can modulate the differentiation of bone‐marrow‐derived MSCs. Herein, the effect of micropatterning on the myogenesis of MSCs isolated from three different sources (bone marrow, fetal tissue, and adipose) is reported. All the well‐aligned cells, regardless of source, predominantly commit to myogenic lineage, as shown by the significant upregulation of myogenic gene markers and positive myosin heavy chain staining. It is demonstrated that our novel micropattern can be used as a generic platform for inducing myogenesis of MSCs from different sources and may also have the potential to be extended to induce other lineage commitment.
This paper presents a technique for collimating a diverging beam from a laser diode using graded-index optical fiber. The optical set-up is relatively simple and easy to operate. The results show that laser beam of large divergent angle in the range of 10–35° can be reduced to a fully collimated beam with a divergent angle of less than 0.05°. The theory of the method as well as some experimental results is presented. 相似文献
A thermal system is developed to rapidly characterize the linewidth sensitivity of advanced resists to process temperature variations in the photolithographic manufacturing sequence. This thermal array consists of a 7×7 grid of individually programmable heating zones distributed within a thermal cycling apparatus. It is used to improve the quality and quantity of data for determining the optimal thermal conditions by effectively producing equivalent operating conditions besides the spatially controlled temperature. The system is demonstrated for the optimization of the post-apply and post-exposure thermal-processing conditions for chemically amplified photoresists used in the fabrication of quartz photomasks . PACS 07.20.Hy; 81.16.Nd; 81.70.Pg 相似文献
For a graph or digraph G, let be the family of strong orientations of G; and for any , we denote by d(D) the diameter of D. Define . In this paper, we survey the results obtained and state some problems and conjectures for the parameter .
Received: October, 2001 Final version received: September 23, 2002 相似文献