Surface Wettability Of Materials Research Articles

Wettability modification of polydimethylsiloxane surface by fabricating micropillar and microhole arrays

Fabrication of microscale surface structures is a promising method for controlling the surface wettability of materials. Herein, the micropillar and microhole arrays of polydimethylsiloxane (PDMS) were fabricated through a soft lithography process, and the modified wettability was investigated. Using PDMS samples with different degrees of crosslinking, a PDMS–PDMS pattern transfer was achieved, and the microhole and micropillar arrays were obtained from a single master substrate. The surface geometries of the prepared PDMS samples were characterized via scanning electron microscopy and laser scanning microscopy. It was demonstrated that the PDMS micropillar and microhole arrays were effective in changing the contact angles of liquids with different surface tensions (water, ethylene glycol, olive oil, and hexadecane). The measured contact angles of the liquids on a PDMS micropillar array were quantitatively interpreted in both the wetting and repellent regimes based on the Cassie-Baxter model.

Three-dimensional numerical investigation of dendritic self-organizational structure growth on a nanopost surface

Nanopost arrays are generally used in applications of reflection gratings and in changing material surface wettability. Nanopost arrays can be used as a passive component to induce dendritic self-organized hierarchical architectures. In this study, through the use of a phase-field model, we performed a three-dimensional numerical simulation to demonstrate that nanopost structures affect the expanding speed of the surface of a dendritic self-organized structure in the growing path of a hierarchical structure. Additionally, we demonstrated that the nanopost array arrangement on the surface changed the hierarchical structure branching. Finally, introducing an externally applied force to the system enabled the use of a nanopost as an active component. Nanopost surroundings were determined to significantly affect the final distribution of dendritic structures and induce hierarchical structures after an external force was introduced to the system.

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets.

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet–height and diameter– and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.

CONTACT ANGLE MEASUREMENT OF DENTAL RESTORATIVE MATERIALS BY DROP PROFILE IMAGE ANALYSIS

The capability of initial microbial adhesion to dental restorative composites surface is influenced by the surface wettability of the materials. The common method to evaluate surface wettability of materials is contact angle measurement. The existing conventional method to measure contact angle is by means of a contact angle (CA)-Goniometer device, which is less practically applicable in clinical circumstances. Therefore, a more practical and applicable method is needed to measure contact angle in clinical circumstances. This research was performed to compare between contact angles measured by means of a CA-Goniometer device and a new practical method of drop profile image analysis. In addition, since there were two different formulas that can be used to calculate contact angle value from a drop profile image, then we also need to evaluate which formula is more reliable to be used. Tests were carried out using three composite discs (Clearfill-Kuraray Medical, Inc.) sample and deionised water for different measurement procedures. One drop of 3µl liquid was dropped onto the surface of the composite discs, and the drop profile image was captured by means of a customized home-made device connected to a digital camera. Two different formulas were used to calculate the contact angle value from the drop profile image, namely the “linier gradient equation” and the “tangential line”. The contact angle values obtained from the two different formulas were compared with the value obtained from the conventional method descriptively. Tests were carried out using three composite discs (Clearfill-Kuraray Medical, Inc.) sample and deionised water for different measurement procedures. One drop of 3µl liquid was dropped onto the surface of the composite discs, and the drop profile image was captured by means of a customized home-made device connected to a digital camera. Two different formulas were used to calculate the contact angle value from the drop profile image, namely the “linier gradient equation” and the “tangential line”. The contact angle values obtained from the two different formulas were compared with the value obtained from the conventional method descriptively. The differences in percentage between the contact angle value calculated by the “linier gradient equation” and “tangential line” formulas, and those calculated by means of the CA-Goniometer are 20,56% and 3,51%, respectively. It is obviously demonstrated that the value obtained by the “tangential line” formula has a smaller difference compared to those obtained by the “linier equation gradient” formula. Among the two different formulas, it is confirmed that the contact angle value calculated with the “tangential line” formula has closer similarity with the value obtained from the CA-Goniometer. This result confirms that the new practical method of drop profile image analysis is promising for measuring contact angle values in clinical circumstances. Related to the drop profile image analysis, the “tangential line” formula is more accurate compared to the “linier gradient equation” formula.

ChemInform Abstract: Chirality‐Driven Wettability Switching and Mass Transfer

AbstractReview: [16 refs.

Chirality‐Driven Wettability Switching and Mass Transfer

Enantioselective wetting: Regulating the surface wettability of materials through chiral molecules provides new insight into the design of chiral materials. By taking advantage of a reversible conformational transition, smart polymers present an ideal platform for translating weak chiral signals into macroscopic properties of materials, thus resulting in a distinctive wettability switching driven by chirality.

Surface characterization and platelet compatibility evaluation of the binary mixed self-assembled monolayers

This report describes a technique that used mixed self-assembled monolayer (SAM) as a model surface to evaluate the effect of steric hindrance on the SAM packing quality and its platelet compatibility. Two series of binary mixed SAMs were formed by mixing the bulky terminated alkanethiol (HS(CH 2) 10PO 3H 2) with a smaller terminated one (HS(CH 2) 9CH 3 and HS(CH 2) 11OH) respectively. Surface characterization results showed the hydrophilicity on these two series of mixed SAMs changed with the solution mole fraction of PO 3H 2 terminated thiol, χ PO 3H 2,soln , and reached to a nearly constant value as χ PO 3H 2,soln was 0.6 for PO 3H 2 + CH 3 SAM and 0.4 for PO 3H 2 + OH SAM. This finding should be due to the gradual saturation of surface PO 3H 2 functionality on these mixed SAMs. The XPS analysis indicated the addition of the CH 3 and OH terminated thiol could reduce the steric hindrance effect of PO 3H 2 functionality on monolayer formation and, henceforth, improve the SAM packing quality. In vitro platelet adhesion assay revealed the platelet compatibility on the PO 3H 2 + OH SAMs was better than that on the PO 3H 2 + CH 3 and the pure PO 3H 2 ones. Moreover, the PO 3H 2 + OH SAM with a low χ PO 3H 2,soln value exhibited the least platelet activating property of these two mixed SAM systems. These findings suggested that material's surface wettability and surface charge density should act collectively in affecting its platelet compatibility.

Effects of radiofrequency glow discharge on impression material surface wettability

Statement of problem. Argon radiofrequency glow discharge (RGD) may simultaneously sterilize and improve surface wettability of impression materials. Purpose. The purpose of this study was to define RGD technical parameters that influence the surface wettability of impression material (optimization phase). Definition of RGD was followed by an assessment of these optimized RGD parameters on the wettability of four impression materials either uncontaminated or contaminated with saliva, compared with conventional liquid disinfection (application phase). Material and methods. For the optimization phase, addition silicone samples were cast against glass with 10 samples per group/parameter ( n = 210). Parameters evaluated were duration of exposure, sample shape and angle, position within the RGD chamber, and argon gas delivery pressure. Changes in surface wettability were determined with contact angle measurements. For the application phase, standardized RGD parameters (90 degrees to the plasma flow, flat, 60 seconds, 5 psi) were used on four groups of impression materials with ( n = 120 samples, 30 per material) or without ( n = 120 samples, 30 per material) prior saliva contamination. Results. RGD treatment of a polyvinyl siloxane impression material significantly ( p< 0.0001) reduced contact angle measurements from 63 ± 1 to 13 ± 4 degrees, regardless of the parameter evaluated. For the application phase, results indicated different responses to RGD relative to nontreated controls. With all materials treated with RGD or disinfectant exposure, the finest 20 μm standard line was reproduced at ×10 magnification with the American National Standards Institute/American Dental Association Specification 19 test die (Sabri Enterprise, Downers Grove, Ill.; n = 80, 10 samples per group). Conclusion. These results suggest RGD selectively alters impression material surface wettability. (J Prosthet Dent 1997;77:414-22.)

Studies on the biocompatibility of materials: fibroblast reorganization of substratum-bound fibronectin on surfaces varying in wettability.

The ability of human fibroblasts to remove and reorganize fibronectin (FN) bound on material surfaces was studied as a novel feature of material surface biocompatibility. Other traditional parameters of biocompatibility analyzed included cell spreading, clustering of fibronectin receptors into focal adhesions, development of stress fibers, and cell growth. Five different materials with surface wettability ranging from hydrophilic (underwater contact angle 25 degrees) to hydrophobic (underwater contact angle 111 degrees) were used, i.e., clean glass (GLASS), aminopropylsilane (APS), octadecylsilane (ODS), polylactate (PL), and silicone (SI). When cells were cultured on these materials in serum-containing medium, formation of FN receptor-rich focal adhesions and actin stress fibers were more evident on the hydrophilic surfaces (GLASS and APS) compared to the hydrophobic ones (PL, ODS, and SI). Cell growth showed a similar pattern, that is, increased cell proliferation with increasing material surface wettability. Preadsorption of FN on the material surfaces increased subsequent cell spreading and cytoskeletal reorganization on hydrophobic surfaces except SI. Removal and reorganization of FN from the material surfaces into extracellular matrixlike structures occurred on GLASS but not on less wettable surfaces, suggesting that this removal/reorganization process may be more sensitive to changes in surface wettability than other parameters of biocompatibility.