scholarly journals Structural and wetting properties of nature's finest silks (order Embioptera)

2018 ◽  
Vol 5 (9) ◽  
pp. 180893 ◽  
Author(s):  
Grace Y. Stokes ◽  
Evangelea N. DiCicco ◽  
Trevor J. Moore ◽  
Vivian C. Cheng ◽  
Kira Y. Wheeler ◽  
...  
Keyword(s):  
Contact Angle ◽  
Related Species ◽  
Fibre Diameter ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Adhesive Properties ◽  
Adhesion Properties ◽  
Static Contact ◽  
Water Adhesion

Insects from the order Embioptera (webspinners) spin silk fibres which are less than 200 nm in diameter. In this work, we characterized and compared the diameters of single silk fibres from nine species— Antipaluria urichi , Pararhagadochir trinitatis , Saussurembia calypso , Diradius vandykei , Aposthonia ceylonica , Haploembia solieri , H. tarsalis , Oligotoma nigra and O. saundersii . Silk from seven of these species have not been previously quantified. Our studies cover five of the 10 named taxonomic families and represent about one third of the known taxonomic family-level diversity in the order Embioptera. Naturally spun silk varied in diameter from 43.6 ± 1.7 nm for D. vandykei to 122.4 ± 3.2 nm for An. urichi. Mean fibre diameter did not correlate with adult female body length. Fibre diameter is more similar in closely related species than in more distantly related species. Field observations indicated that silk appears shiny and smooth when exposed to rainwater. We therefore measured contact angles to learn more about interactions between silk and water. Higher contact angles were measured for silks with wider fibre diameter and higher quantity of hydrophobic amino acids. High static contact angles (ranging up to 122° ± 3° for An. urichi ) indicated that silken sheets spun by four arboreal, webspinner species were hydrophobic. A second contact angle measurement made on a previously wetted patch of silk resulted in a lower contact angle (average difference was greater than 27°) for all four species. Our studies suggest that silk fibres which had been previously exposed to water exhibited irreversible changes in hydrophobicity and water adhesion properties. Our results are in alignment with the ‘super-pinning’ site hypothesis by Yarger and co-workers to describe the hydrophobic, yet water adhesive, properties exhibited by webspinner silk fibres. The physical and chemical insights gained here may inform the synthesis and development of smaller diameter silk fibres with unique water adhesion properties.

Wettability measurements on two sandstones: an experimental investigation before and after CO2 flooding

2020 ◽  
Vol 60 (1) ◽  
pp. 117
Author(s):  
Cut Aja Fauziah ◽  
Emad A. Al-Khdheeawi ◽  
Ahmed Barifcani ◽  
Stefan Iglauer
Keyword(s):  
Contact Angle ◽  
Co2 Storage ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Co2 Injection ◽  
Co2 Flooding ◽  
Berea Sandstone ◽  
Before And After ◽  
Carbon Dioxide Co2

Wettability of rock–fluid systems is an important for controlling the carbon dioxide (CO2) movement and the capacities of CO2 geological trapping mechanisms. Although contact angle measurement is considered a potentially scalable parameter for evaluation of the wettability characteristics, there are still large uncertainties associated with the contact angle measurement for CO2–brine–rock systems. Thus, this study experimentally examined the wettability, before and after flooding, of two different samples of sandstone: Berea and Bandera grey sandstones. For both samples, several sets of flooding of brine (5 wt % NaCl + 1 wt % KCl in deionised water), CO2-saturated (live) brine and supercritical CO2 were performed. The contact angle measurements were conducted for the CO2–sandstone system at two different reservoir pressures (10 and 15 MPa) and at a reservoir temperature of 323 K. The results showed that both the advancing and receding contact angles of the sandstone samples after flooding were higher than that measured before flooding (i.e. after CO2 injection the sandstones became more CO2-wet). Moreover, the Bandera grey samples had higher contact angles than Berea sandstone. Thus, we conclude that CO2 flooding altered the sandstone wettability to be more CO2-wet, and Berea sandstone had a higher CO2 storage capacity than Bandera grey sandstone.

Hydrophobicity Enhancement of the Polyvinyl Alcohol/Rice Starch/Silk Fibroin Films by Glycerol

2013 ◽  
Vol 446-447 ◽  
pp. 360-365
Author(s):  
Pusita Kuchaiyaphum ◽  
Takeshi Yamauchi ◽  
Ruangsri Watanesk ◽  
Surasak Watanesk
Keyword(s):  
Contact Angle ◽  
Polyvinyl Alcohol ◽  
Silk Fibroin ◽  
Water Solubility ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Rice Starch ◽  
Water Contact ◽  
Degree Of Swelling

Eco-friendly films have been prepared using various biopolymers and their properties have been improved in order to meet the requirements for appropriate applications. However, the frequently encountered weakness of the properties of most biopolymer film is its water solubility. In this study, the polyvinyl alcohol/rice starch/silk fibroin (PVA/RS/SF) films were modified by the addition of glycerol aiming to increase the hydrophobicity of the films. Some properties of the modified films including water contact angle, degree of swelling and water solubility were compared with the unmodified PVA/RS/SF film. Results from the contact angle measurement showed that the films with glycerol could be transformed to be hydrophobic after soaking in ethanol medium. The increase in soaking time tends to increase the hydrophobicity of the films. However, at about 60 min soaking, the water contact angles on the films were quite constant with the values of about 107.9±5.2º comparing with 65.3±2.4º of the ethanol-untreated PVA/RS/SF films. In addition, the ethanol-treated glycerol-modified films also show higher degree of swelling with constant solubility and better mechanical properties.

scholarly journals Preparation of Superhydrophobic Teflon® AF 1600 Sub-Micron Fibers and Yarns Using the Forcespinningtm Technique

2013 ◽  
Vol 8 (4) ◽  
pp. 155892501300800 ◽  
Author(s):  
Yatinkumar Rane ◽  
Aleksey Altecor ◽  
Nelson S. Bell ◽  
Karen Lozano
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Average Diameter ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Sem Analysis ◽  
Fiber Formation ◽  
Excellent Thermal Stability ◽  
Wetting Properties

Superhydrophobic materials combined with manufacturing processes that can increase surface roughness of the material, offer an opportunity to effectively control wetting properties. Rapid formation of Teflon® AF (TAF) fibrous mats with sub-micron fiber diameter using the Forcespinning™ technique is presented. The fiber formation technique is based on the use of centrifugal forces. SEM analysis shows uniform formation of TAF 1600 fibers with average diameter of 362±58nm. Contact angle measurement confirms the superhydrophobic nature of the mats with contact angles as high as 169° ± 3° and rolling angles of 2°. TAF 1600 mats were forcespun at a rate of 1gr/min. The relationship between the contact angle and hierarchical surface roughness of the TAF mat is also discussed. TAF yarns were also manufactured and characterized. Yarns with diameters of 156 microns withstood 17.5 MPa of engineering stress with a Young's modulus of 348 MPa in the elastic region and excellent thermal stability.

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

2014 ◽  
Vol 3 (2) ◽  
Author(s):  
H. D. K. Yulianto dan M. Rinastiti
Keyword(s):  
Contact Angle ◽  
Image Analysis ◽  
Conventional Method ◽  
Digital Camera ◽  
Practical Method ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Surface Wettability ◽  
Dental Restorative

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.

Automated Drop-on-Fiber contact angle measurement using a microrobotic platform

2014 ◽  
Vol 29 (2) ◽  
pp. 225-231 ◽  
Author(s):  
Pooya Saketi ◽  
Juha Hirvonen ◽  
Yuli Lai ◽  
Christian Ganser ◽  
Christian Teichert ◽  
...  
Keyword(s):  
Contact Angle ◽  
Natural Fibers ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Structural Factors ◽  
Fibrous Materials ◽  
Liquid Droplets ◽  
Fiber Volume ◽  
Pulp Paper

Abstract Measuring contact angles on single fibers enables the separation of structural factors from surface chemistry factors. Current Drop-on-Fiber (DOF) contact angle measurement methods for natural fibers generally, and for pulp/paper fibers specifically, present a number of challenges. These are manipulation and mounting of the microscale fibers, straightening natural fibers to produce repeatable axisymmetric droplet conformation, measuring the droplet volume excluding the fiber volume and also human errors due to manually performed tasks. This paper presents a novel method to measure contact angles in DOF systems and overcome the above mentioned challenges using microrobots. The proposed microrobotic platform is capable of handling natural and synthetic fibrous materials in microscale, and dispensing probe liquid droplets down to 12 nl. It measures contact angle values using computer vision and a droplet-profiledetection algorithm. It reports the contact angle values as a function of volume of the droplet. The paper validates the capabilities of the proposed platform by applying three commonly used probe liquids: deionized water, ethylene glycol and diiodomethane for measuring contact angles on glass and pulp fibers. Finally, the results are compared with a picoliter contact angle measurement approach.

Adhesion Properties of Copper/Polyimide Film Modified by Reactive Ion Etching(RIE)

2007 ◽  
Vol 124-126 ◽  
pp. 1593-1596 ◽  
Author(s):  
W.J. Lee ◽  
Yoon B. Kim ◽  
W.Y. Lee ◽  
S.H. Han ◽  
J.H. Han ◽  
...  
Keyword(s):  
Contact Angle ◽  
Functional Group ◽  
Ion Beam ◽  
Polyimide Film ◽  
Contact Angle Measurement ◽  
Angle Measurement ◽  
Water Contact ◽  
Adhesion Properties ◽  
Surface Metal ◽  
Surface Modified

Surface modification of polyimide(PI) films was treated with oxygen RIE by varying ion doses from 1x1016 to 1x1018 ions/cm2 at an ion beam energy of 250 eV. Following the modification of PI surface, metal films consisting of NiCr/Cu and Cu were deposited on modified PI films by D.C. magnetron sputtering and electroplating, respectively. The surface modified PI film was characterized by XPS, AFM, SEM and contact angle measurement, respectively. The water contact angle of PI film decreased significantly from 64° to 4.4° with an increase of ion dose, indicating that the surface energy of PI film increased. The XPS spectrum showed that functional group, particularly C-O bonding, on modified PI surface was significantly increased by interaction between scissored unstable chains and reactive ions. The modified PI film surfaces by oxygen RIE showed significant improvement in adhesion to a overcoated metal film of NiCr/Cu.

scholarly journals Correlation between Contact Angle and Surface Roughness of Silicon Carbide Wafers

2021 ◽  
Author(s):  
Jung Gon Kim ◽  
Woo Sik Yoo ◽  
Woo Yeon Kim ◽  
Won Jae Lee
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Contact Angle Measurement ◽  
Contact Angles ◽  
Angle Measurement ◽  
Surface Polarity ◽  
Force Microscopy ◽  
Water Drops ◽  
The Difference ◽  
Sic Wafer

Abstract Two-inch diameter 6H-SiC wafers were sliced from a SiC ingot and the wafers were ground and polished using different diamond slurries (1 m and 0.1 m in particles size) to investigate their dependence on wetting on surface roughness (Ra) and polarity using precisely dispensed de-ionized (DI) water drops. The Ra of the Si-face (0001) SiC wafer, after grinding and polishing, was 5.6 and 1.6 nm, respectively, as measured by atomic force microscopy (AFM). For C-face (000-1) SiC wafers, the Ra was 7.2 nm after grinding and 3.3 nm after polishing. The average contact angle measurement of the SiC wafers after final polishing showed clear differences between surface polarity; the contact angle for the Si-face (0001) was ~7o greater than that for the C-face (000-1). The difference in contact angles between the Si-face (0001) and the C-face (000-1) tends to increase as the reduction of surface roughness approaches the final stage of polishing. The uniformity of Raman peak intensity in the folded transverse optical phonon band at ~780 cm-1 in scanned areas correlated well with the surface roughness measured by AFM. The contact angle measurement can be used as a convenient surface polarity and surface roughness testing technique for SiC wafers.

scholarly journals Direct generation of superhydrophobic microstructures in metals by UV laser sources in the nanosecond regime

2016 ◽  
Vol 5 (1) ◽  
Author(s):  
Jose L. Ocaña ◽  
R. Jagdheesh ◽  
J.J. García-Ballesteros
Keyword(s):  
Contact Angle ◽  
Laser Pulses ◽  
Contact Angle Measurement ◽  
Angle Measurement ◽  
Contact Friction ◽  
Structured Surfaces ◽  
Wetting Properties ◽  
Aluminum Sheets ◽  
Static Contact ◽  
Laser Sources

AbstractThe current availability of new advanced fiber and DPSS lasers with characteristic pulse lengths ranging from ns to fs has provided a unique frame in which the development of laser-generated microstructures has been made possible for very diverse kinds of materials and applications. At the same time, the development of the appropriate laser-processing workstations granting the appropriate precision and repeatability of the respective laser interaction processes in line with the characteristic dimension features required in the microstructured samples has definitively consolidated laser surface microstructuring as a reference domain, nowadays, unavoidable for the design and manufacturing of current use microsystem: MEMSs, fluidic devices, advanced sensors, biomedical devices and instruments, etc., are all among the most well-known developments of the micromanufacturing technology. Completing the broad spectrum of applications developed mostly involving the generation of geometrical features on a subtrate with specific functional purposes, a relatively new, emerging class of laser-microstructuring techniques is finding an important niche of application in the generation of physically structured surfaces (particularly of metallic materials) with specific contact, friction, and wear functionalities, for whose generation the concourse of different types of laser sources is being found as an appropriate tool. In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces (specifically Al) for the modification of their wettability properties is described as an attractive application basis for the generation of self-cleaning properties of extended functional surfaces. Flat aluminum sheets of thickness 100 μm were laser machined with ultraviolet laser pulses of 30 ns with different laser parameters to optimize the process parameters. The samples produced at the optimum conditions with respect to contact angle measurement were subjected to microstructure and chemical analysis. The wetting properties were evaluated by static contact angle measurements on the laser-patterned surface. The laser-patterned microstructures exhibited superhydrophobicity with a maximum contact angle of 180° for the droplet volumes in the range of 8–12 μl.

Sign in / Sign up

Export Citation Format

Share Document