Effects of thermo-hygro-mechanical densification on the surface characteristics of trembling aspen and hybrid poplar wood veneers

The effect of thermo-hygro-mechanical (THM) densification temperature on the surface color, roughness, wettability, and chemical composition of trembling aspen (Populus tremuloides) and hybrid poplar (Populus maximowiczii × P. balsamifera) veneers was investigated. Veneers were subjected to four THM densification temperatures (160 °C, 180 °C, 200 °C, and 220 °C). Veneer color darkened with increasing THM densification temperature. Surface roughness decreased between 160 °C and 200 °C. Wettability decreased after THM densification, but no significant difference was found between treated specimens. ATR-FTIR and XPS results confirmed that THM densification caused major chemical changes in veneer surfaces, and more pronounced at temperatures higher than 160 °C.     

Directional motion of water drop on ratchet-like superhydrophobic surfaces

In this article, directional movements of drops on the ratchet-like superhydrophobic surfaces were observed. High-speed CCD images showed the caterpillar-like crawl of a drop on the inclined superhydrophobic surfaces as it rolled along the ridge of ratchet. In contrast, along the opposite direction, the movement of the drop only depended on the end of triple phase contact line while the front of contact line was pinned. The sliding angle (SA) measurements indicated that the ratchet-like superhydrophobic surfaces had directional drop retention traits. Moreover, the reduction of the rise angle ω₁, the height d of the ratchet's ridge and the volume V of the drop can greatly enhance the directional difference of drop retention on the ratchet-like superhydrophobic surfaces. Therefore, it was concluded that the superhydrophobicity and the periodic ratchet-like microstructures were the keys to the directional drop sliding at one-dimensional level. We believe that these findings would be helpful to better understand the ratchet-like effect on the superhydrophobic surfaces and guide some novel engineering applications.     

Modular Assembly of Host–Guest Metal–Phenolic Networks Using Macrocyclic Building Blocks

The manipulation of interfacial properties has broad implications for the development of high‐performance coatings. Metal–phenolic networks (MPNs) are an emerging class of responsive, adherent materials. Herein, host–guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties. Macrocyclic cyclodextrins (host) are conjugated to catechol or galloyl groups and subsequently used as components for the assembly of functional MPNs. The assembled cyclodextrin‐based MPNs are highly permeable (even to high molecular weight polymers: 250–500 kDa), yet they specifically and noncovalently interact with various functional guests (including small molecules, polymers, and carbon nanomaterials), allowing for modular and reversible control over interfacial properties. Specifically, by using either hydrophobic or hydrophilic guest molecules, the wettability of the MPNs can be readily tuned between superrepellency (>150°) and superwetting (ca. 0°).     

Controlled Directional Water‐Droplet Spreading on a High‐Adhesion Surface

Controlled directional spreading of a droplet on a smart high‐adhesion surface was made possible by simply controlling anodic oxidation. The wettability gradient of the surface was controlled from 0.14 to 3.38° mm^?1 by adjusting the anodic oxidation conditions. When a water droplet made contact with the substrate, the droplet immediately spread in the direction of the wettability gradient but did not move in other directions, such as those perpendicular to the gradient direction, even when the surface was turned upside down. The spreading behavior was mainly controlled by the wettability gradient. Surfaces with a V‐ or inverse‐V‐shaped wettability gradient were also formed by the same method, and two droplets on these surfaces spread either toward or away from one another as designed. This method could be used to oxidize many conductive substrates (e.g., copper, aluminum) to form surfaces with variously shaped wettability gradients. It has potential for application in microfluidic devices.     

微液滴在仿蛛丝结构TiO_2纤维表面的定向运动与粘附

制备了具有响应性的仿蛛丝周期纺锤节TiO2纤维。通过改变纤维表面微观结构、紫外光照和超声波等手段,仿蛛丝结构TiO2纤维表面浸润性会发生响应性变化。纤维表面的这种浸润性变化,不仅实现了水滴从纺锤节两端到中心处的定向运动,而且可以使得水滴被纤维纺锤节粘附。当仿蛛丝结构TiO2纤维表面为亲水状态时,无论纺锤节光滑还是粗糙,水都是从纺锤节两端向中心方向运动;当仿蛛丝结构TiO2纤维表面疏水时,水滴会被具有粗糙表面的纺锤节两端粘附。     

Twenty years of glass capillary columns. An empirical model for their preparation and properties

Both the invention of the capillary drawing machine and the preparation and successful use of the first glass capillary column were achieved by Desty and his group in 1959. This paper attempts to describe the glass capillary column in a general way, including the spreading of liquid phases of different polarity and solid surfaces with different chemical and geometrical structures, and surface activity (as a source of essential column characteristjcs such as film stability, adsorptive and catalytic activity, acidity, and thermostability). The model is entirely based on experimental evidence. It is shown that today's apolar columns may closely approach ideal performance, such as is conceivable at the present time, while a severe gap still exists between the actual and the ideal characteristics of polar columns. The problem lies in the necessity of using considerably active support surfaces for polar coatings, yielding columns with reduced upper temperature limits, and of restricted suitability concerning the nature of sample. It is hoped that progress in the field of surface roughening may produce an inert support which is wettable by polar phases.     

Cell culture on polymers prepared by radiation-induced grafting of various monomers

The adhesion and growth of tissue cells on polymers prepared by radiation grafting was investigated. The apparent rates of initial attachment and growth of Chang liver and C₆ cells were promoted on surfaces with increased wettability and with a heterogeneous structure for grafted polyvinyl fluoride film. The degree of cell attachment and growth on surfaces having a dense microblock structure, formed by grafting of methyl methacrylate in acetone solvent, was greater than that caused by other factors, such as wettability.     

Surface modification of polyester by oxygen‐ and nitrogen‐plasma treatment

In this paper, we present a study on the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment. The samples were treated by nitrogen and oxygen plasma for different time periods between 3 and 90 s. The plasma was created by a radio frequency (RF) generator. The gas pressure was fixed at 75 Pa and the discharge power was set to 200 W. The samples were treated in the glow region, where the electrons temperature was about 4 eV, the positive ions density was about 2 × 10¹⁵ m^?3, and the neutral atom density was about 4 × 10²¹ m^?3 for oxygen and 1 × 10²¹ m^?3 for nitrogen. The changes in surface morphology were observed by using atomic force microscopy (AFM). Surface wettability was determined by water contact angle measurements while the chemical composition of the surface was analyzed using XPS. The stability of functional groups on the polymer surface treated with plasma was monitored by XPS and wettability measurements in different time intervals. The oxygen‐plasma‐treated samples showed much more pronounced changes in the surface topography compared to those treated by nitrogen plasma. The contact angle of a water drop decreased from 75° for the untreated sample to 20° for oxygen and 25° for nitrogen‐plasma‐treated samples for 3 s. It kept decreasing with treatment time for both plasmas and reached about 10° for nitrogen plasma after 1 min of plasma treatment. For oxygen plasma, however, the contact angle kept decreasing even after a minute of plasma treatment and eventually fell below a few degrees. We found that the water contact angle increased linearly with the O/C ratio or N/C ratio in the case of oxygen or nitrogen plasma, respectively. Ageing effects of the plasma‐treated surface were more pronounced in the first 3 days; however, the surface hydrophilicity was rather stable later. Copyright © 2008 John Wiley & Sons, Ltd.     

Cytocompatibility of surface ground PE doped with calcium salt of 6-carboxycellulose

We studied the physical–chemical properties of polyethylene (PE) films doped with calcium salt of 6-carboxycellulose (Ca-oxy) in concentrations 0–20 wt.% and their interactions with cells. The interaction between the PE/Ca-oxy composite film and 3T3 cells has not been described so far. Modification by surface grinding to enhance material cytocompatibility was studied. The surface wettability of doped films was tested by contact angle measurements and the surface morphology by SEM microscopy and profilometry. Adhesion and proliferation of tissue cells (3T3 mouse fibroblasts) were studied in vitro on pristine and ground doped PE films. The ground samples have a higher contact angle values and the number of proliferated cells is greater on the ground samples than on pristine ones. The presence of Ca-oxy in PE film increases the adhesion of 3T3 cells on the doped substrate and on ground samples adhere more cells than on pristine ones.