Effect of Ni-Cr Layer on Adhesion Strength of Flexible Copper Clad Laminate

In this study, the effect of a Ni-Cr layer on the adhesion strength of flexible copper clad laminate (FCCL) was evaluated after thermal treatment. The changes in the chemical composition, morphology, and adhesion properties were characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and 90 deg peel test. The results showed that both the peel strength and thermal resistance of the FCCL increased with increasing Cr ratio. The thermal treatment of the FCCL increased the proportion of C-N bonds and reduced that of the C-O and carbonyl (C=O) bonds in the polyimide. The roughness of the fracture surface decreased with increasing thermal treatment temperature and holding time. The chemical function and roughness of the fracture surface were affected by the Ni-to-Cr ratio.     

Patterned Hydrogels for Controlled Platelet Adhesion from Whole Blood and Plasma

This work describes the preparation and properties of hydrogel surface chemistries enabling controlled and well‐defined cell adhesion. The hydrogels may be prepared directly on plastic substrates, such as polystyrene slides or dishes, using a quick and experimentally simple photopolymerization process, compatible with photolithographic and microfluidic patterning methods. The intended application for these materials is as substrates for diagnostic cell adhesion assays, particularly for the analysis of human platelet function. The non‐specific adsorption of fibrinogen, a platelet adhesion promoting protein, is shown to be completely inhibited by the hydrogel, provided that the film thickness is sufficient (>5 nm). This allows the hydrogel to be used as a matrix for presenting selected bioactive ligands without risking interference from non‐specifically adsorbed platelet adhesion factors, even in undiluted whole blood and blood plasma. This concept is demonstrated by preparing patterns of proteins on hydrogel surfaces, resulting in highly controlled platelet adhesion. Further insights into the protein immobilization and platelet adhesion processes are provided by studies using imaging surface plasmon resonance. The hydrogel surfaces used in this work appear to provide an ideal platform for cell adhesion studies of platelets, and potentially also for other cell types.     

Effect of adhesive and cohesive strength on the tribological behaviour of non‐reactively sputtered TiC thin films

Titanium carbide (TiC) thin films were deposited on D9 steel substrates at room temperature (RT), 200 °C and 400 °C. A compound TiC target was sputtered to deposit films in a non‐reactive argon atmosphere. As‐deposited films were characterised for structural, chemical and mechanical properties. Nanoindentation and scratch tests were performed to evaluate the cohesive and adhesive strength of the films, respectively. Tribological properties of the films were investigated using a tribometer. An increase in nano‐hardness from 7.2 to 10.5 GPa was observed as deposition temperature was increased. The films deposited at RT and 200 °C showed poor adhesion leading to the inferior tribological performance. In contrast, films deposited at 400 °C showed better adhesion which improved the wear resistance. Tribological behaviour of TiC thin films was correlated with contact deformation modes of coatings. These modes revealed significant role of adhesive and cohesive strength associated with the coatings. Copyright © 2009 John Wiley & Sons, Ltd.     

Multi‐metal shell coated with surface modification of polystyrene bead cores to improve its adhesion metal shell

We investigated the delamination problem at the metal‐polymer interface and the mechanical buckling of the metal layer at a localized area of the metallic shell under compression between two parallel plates. First, polystyrene (PS) beads were synthesized by dispersion polymerization and then their sulfonation process. After sequential electroless deposition, the average size of multi‐metal coated sulfonated polystyrene (SPS) bead was ca 4.95 µm. Using the electromechanical indentation, the electrical resistance of a single metal‐coated SPS bead decreased with increasing compressive strain without delamination at the metal‐polymer interface, and its electrical resistance showed 5.65 Ω. Copyright © 2009 John Wiley & Sons, Ltd.     

Suppression of cell and platelet adhesion to star-shaped 8-armed poly(ethylene glycol)-poly(L-lactide) block copolymer films

To explore the potential of a star-shaped 8-armed poly(ethylene glycol)35K-block-poly(L-lactide)37K (8-armed PEG35K-b-PLLA37K: M(n) of PEG = 35 000, M(n) of PLLA = 37 000) film as a novel bioabsorbable adhesion-prevention membrane, the water structure, surface contact angle, protein adsorption, and cell and platelet anti-adhesion properties of such a hydrated film are investigated. Based on the results, it is found that the 8-armed PEG35K-b-PLLA37K film exhibits a biologically inert surface, which is the result of a large number of PEG chains and a free water layer on the film surface. This leads to a reduction in protein absorption and cell and platelet adhesion onto the film surface. This implies that the star-shaped 8-armed PEG35K-b-PLLA37K film can be utilized as a novel bioabsorbable adhesion-prevention membrane.     

Polyelectrolyte multilayer formation: Electrostatics and short-range interactions

We investigate the phenomenon of multilayer formation via layer-by-layer deposition of alternating charged polyelectrolytes. Using mean-field theory, we find that a strong short-range attraction between the two types of polymer chains is essential for the formation of multilayers. For strong enough short-range attraction, the adsorbed amount per layer increases (after an initial decrease), and finally it stabilizes in the form of a polyelectrolyte multilayer that can be repeated hundreds of times. For weak short-range attraction between any two adjacent layers, the adsorbed amount (per added layer) decays as the distance from the surface increases, until the chains stop adsorbing altogether. The dependence of the threshold value of the short-range attraction as function of the polymer charge fraction and salt concentration is calculated.     

Measurement of adhesion energies and Young's modulus in thin polymer films using a novel axi-symmetric peel test geometry

We present a novel method of probing adhesion energies of solids, particularly polymers. This method uses the axi-symmetric deformation of a thin spincast polymer membrane brought into contact with a flat substrate to probe the work of adhesion. The use of a thin membrane minimizes uncertainty in the radius of contact, while the use of spincast films provides very smooth surfaces by means of a very simple method. The experimental profile of the deformed membrane shows good agreement with the expected logarithmic profile. The experimental setup enables the measurement of Young's modulus and the solid-solid work of adhesion for thin films. The value obtained for Young's modulus of polystyrene (PS) was found to be in agreement with other conventional measurement techniques. In addition, measurement of the work of adhesion at the PS/silicon oxide interface was possible. The apparatus is well suited to studying the dependence of Young's modulus, work of adhesion and fracture energy on membrane thickness, temperature, pulling rate, and ageing of the interface, and can readily be modified to study biologically relevant samples.     

Frontal polymerization of acrylic monomers for the consolidation of stone

Polymeric products are largely used for consolidation of stone in the field of cultural heritage. Nevertheless, the main problem of polymeric compounds is related to their macromolecular nature, it being difficult for a polymer to penetrate inside the pores which may have a very small diameter. These considerations are the starting points for in situ polymerization. According to this technique, not the pre‐formed polymer, but the monomer is introduced into the stone and it is polymerized in situ in a subsequent step. Frontal polymerization (FP) is a particular technique in which the heat released by the exothermal reaction of monomer to polymer conversion is exploited to promote the formation of a hot traveling front able to propagate and self‐sustain the reaction. In the present work, FP is performed inside the pores of the stone and the results lead to the conclusion that the hot front is still active in the presence of an inorganic material which dissipates partially the heat released during the polymerization. In addition some recent applications of FP are discussed in comparison with the traditional polymerization for the in situ consolidation and protection of stones. Copyright © 2005 John Wiley & Sons, Ltd.     

多弧离子镀(Ti,Al,Cr)N硬质膜的沉积工艺与力学性能

采用多弧离子镀技术并使用合金靶制备(Ti,Al,Cr)N多组元硬质膜.利用扫描电镜、X射线衍射仪对(Ti,Al,Cr)N膜层表面及断面形貌、成分、结构等进行观察测定,系统考察了沉积工艺对(Ti,Al,Cr)N膜层质量、硬度、膜/基结合力的影响,通过与TiN,(Ti,Al)N和(Ti,Cr)N等硬质膜进行比较,发现采用Ti-Al-Cr合金靶所制备的(Ti,Al,Cr)N硬质膜具有更高的硬度和更好的附着力,同时对沉积工艺有较强的适应性.     

Tunable Adhesive Superhydrophobic Surfaces for Superparamagnetic Microdroplets

Inspired by the gecko's ability to reversibly stick and unstick to a variety of solid surfaces during locomotion, a new superhydrophobic iron surface that has a tunable adhesive force with the superparamagnetic microdroplet as a function of the magnetic field was fabricated by a simple and inexpensive method. The as‐prepared surface is low adhesive, and a superparamagnetic microdroplet can roll easily on the surface. After the surface is magnetized, it becomes highly adhesive, which can pin a superparamagnetic microdroplet. Further demagnetizing the surface that has been magnetized, a superparamagnetic microdroplet can roll on the surface again, indicating that the surface returns to its initial low adhesive state. Reversible transition between the high adhesive pinning state and low adhesive rolling state can be achieved by simply magnetizing and demagnetizing the surface alternately. The tunable effect maybe attribute to the cooperation of the soft ferromagnetic property of iron plate and the microstructure on the surface. Such intelligent surface could potentially be used in a wide range of applications such as biochemical separation, no‐loss transport of microdroplet, and in situ detection.