The Surface Modification with Fluorocarbon Thin Films for the Prevention of Stiction in Mems

1998 ◽  
Vol 518 ◽  
Author(s):  
Sang-Ho Lee ◽  
Myong-Jong Kwon ◽  
Jin-Goo Park ◽  
Yong-Kweon Kim ◽  
Hyung-Jae Shin
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Fluorocarbon Films ◽  
Perfluorodecanoic Acid ◽  
Large Hysteresis ◽  
Static Contact ◽  
Receding Contact ◽  
Highly Hydrophobic ◽  
Receding Contact Angle

AbstractHighly hydrophobic fluorocarbon films were prepared by the vapor phase (VP) deposition method in a vacuum chamber using both liquid (3M's FC40, FC722) and solid sources (perfluorodecanoic acid (CF3(CF2)8COOH), perfluorododecane (C12F26)) on Al, Si and oxide coated wafers. The highest static contact angles of water were measured on films deposited on aluminum substrate. But relatively lower contact angles were obtained on the films on Si and oxide wafers. The advancing and receding contact angle analysis using a captive drop method showed a large contact angle hysteresis (ΔH) on the VP deposited fluorocarbon films. AFM study showed poor film coverage on the surface with large hysteresis. FTIR-ATR analysis positively revealed the stretching band of CF2 groups on the VP deposited substrates. The thermal stability of films was measured at 150°C in air and nitrogen atmospheres as a function of time. The rapid decrease of contact angles was observed on VP deposited FC and PFDA films in air. However, no decrease of contact angle on them was observed in N2.

scholarly journals Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces: Study of the Links between Morphology and Wettability

Biomimetics ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 38
Author(s):  
Quentin Legrand ◽  
Stephane Benayoun ◽  
Stephane Valette
Keyword(s):  
Contact Angle ◽  
Ginkgo Biloba ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Textured Surfaces ◽  
Replication Process ◽  
Wetting Behavior ◽  
Static Contact ◽  
Biomimetic Approach ◽  
Highly Hydrophobic

This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135∘, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20∘. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40∘ for flat PDMS to less than 10∘ for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

Degradation of Hydrophobic Surface Coatings Under Water Exposure

2018 ◽  
Author(s):  
Matthew A. Trapuzzano ◽  
Rasim Guldiken ◽  
Andrés Tejada-Martínez ◽  
Nathan B. Crane
Keyword(s):  
Contact Angle ◽  
Material Selection ◽  
Contact Angle Hysteresis ◽  
Hydrophobic Surface ◽  
Contact Angles ◽  
Water Exposure ◽  
Angle Measurements ◽  
Degradation Rates ◽  
Contact Angle Measurements ◽  
Receding Contact

Many important processes depend on the wetting of liquids on surfaces. Wetting is commonly controlled through material selection, coatings, and/or surface texture, however these means are sensitive to environmental conditions. Some “hydrophobic” fluoropolymer coatings are sensitive to extended water exposure as evidenced by declining contact angles and increasing contact angle hysteresis. Understanding degradation of these coatings is critical to processes that employ them. To accomplish this, contact angle measurements were taken before, during, and after slides coated with FluoroSyl 3750 or Cytop were submerged in water, or vibrated while covered in water. Both methods demonstrated similar changes in advancing contact angle though vibration increased degradation rates significantly. However, it does not simply accelerate the process as different trends are apparent in receding contact angles. The FluoroSyl 3750 showed no clear degradation under either condition. Surface profilometry did not detect any surface morphology differences that might cause contact angle change.

Superhydrophobic Surfaces Properties for Anti-Icing

2011 ◽  
Author(s):  
Mohammad Amin Sarshar ◽  
Christopher Swarctz ◽  
Scott Hunter ◽  
John Simpson ◽  
Chang-Hwan Choi
Keyword(s):  
Contact Angle ◽  
Wind Tunnel ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Superhydrophobic Surfaces ◽  
Ice Formation ◽  
Flow Conditions ◽  
Water Droplets ◽  
Dynamic Flow ◽  
Static Contact

In this paper, the iceophobic properties of superhydrophobic surfaces are compared to those of uncoated aluminum and steel plate surfaces as investigated under dynamic flow conditions by using a closed loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared at the Oak Ridge National Laboratory by coating aluminum and steel plates with nano-structured hydrophobic particles. The contact angle and contact angle hysteresis measured for these surfaces ranged from 165–170° and 1–8°, respectively. The superhydrophobic plates along with uncoated control ones were exposed to an air flow of 12 m/s and 20°F with micron-sized water droplets in the icing wind tunnel and the ice formation and accretion were probed by using high speed cameras for 90 seconds. Results show that the developed superhydrophobic coatings significantly delay the ice formation and accretion even with the impingement of accelerated super-cooled water droplets, but there is a time scale for this phenomenon which has a clear relation with contact angle hysteresis of the samples. Among the different superhydrophobic coating samples, the plate having the lowest contact angle hysteresis showed the most pronounced iceophobic effects, while the correlation between static contact angles and the iceophobic effects was not evident. The results suggest that the key parameter for designing iceophobic surfaces is to retain a low contact angle hysteresis, rather than to have only a low contact angle, which can result in more efficient anti-icing properties in dynamic flow conditions.

A New Approach To Improve The Assessments of CO2 Geo-Sequestration Capacity of Clay Minerals

2021 ◽  
Author(s):  
Emad A. Al-Khdheeawi ◽  
Cut Aja Fauziah ◽  
Doaa Saleh Mahdi ◽  
Ahmed Barifcani
Keyword(s):  
Contact Angle ◽  
Clay Mineral ◽  
Water System ◽  
Density Variation ◽  
Contact Angles ◽  
Gas Density ◽  
Capillary Trapping ◽  
Receding Contact ◽  
Mineral Trapping ◽  
Receding Contact Angle

Abstract CO2 geological storage (CCS)isconsidered as the most promising technique to reduce atmospheric CO2emissions. However, due to the density variation between the injected supercritical CO2 and the formation water,CO2 tends to move vertically toward the air. This vertical CO2 leakage can be prevented by four trapping mechanisms (i.e. structural trapping,capillary trapping, solubility trapping, and mineral trapping). The capacities of structural and residual trapping are highly affected by rock wettability. Clay wettability is one of the crucial parametersin evaluation of CO2 geo-sequestration. However, the literature data show that there are many uncertainties associated with experimental measurements. One of these uncertainties is the influenceof the effect of gas density on the clay mineral wettability. Thus, here, we compared the wettability of a clay mineral (i.e. illite) of three different gas densities scenarios (i.e. low (Helium), moderate (Nitrogen), and high (CO2) gas densities). To do so, we measured the advancing and receding contact angle (i.e. wettability) of illite for CO2/water, nitrogen/water, and Helium/water systems at a constant (333 K) and four different pressures (5, 10, 15, and 20 MPa). The brine composition used was 4 wt% NaCl, 4 wt% CaCl2, 1 wt% MgCl2 and 1 wt% KCl, for all gas density scenarios. The results indicate that gas density has a significant effect on the clay mineral wettability and that both advancing and receding contact angles increase with an increase in gas density. The results show that a higher density gas scenario has a higher contact angle of illite, measured at the same temperature and pressure. For instance, the advancing contact angle of illite at 333 K and 20 MPa was 65° for the CO2/water system, 53° for the nitrogen/water system, and 50° for Helium/water Helium/water system. Thus, we conclude that the gas density affects the Clay wettability measurement and that the higher gas density leads to a higher contact angle measurements (i.e. a more CO2-wet system) of the clay and thus reduces the estimated CO2 geo-sequestration capacity and containment security.

scholarly journals Thick drops climbing uphill on an oscillating substrate

2018 ◽  
Vol 840 ◽  
pp. 131-153 ◽  
Author(s):  
J. T. Bradshaw ◽  
J. Billingham
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Boundary Integral ◽  
Static Contact Angle ◽  
Rise Velocity ◽  
Contact Lines ◽  
Weakly Nonlinear ◽  
Static Contact

Experiments have shown that a liquid droplet on an inclined plane can be made to move uphill by sufficiently strong, vertical oscillations (Brunet et al., Phys. Rev. Lett., vol. 99, 2007, 144501). In this paper, we study a two-dimensional, inviscid, irrotational model of this flow, with the velocity of the contact lines a function of contact angle. We use asymptotic analysis to show that, for forcing of sufficiently small amplitude, the motion of the droplet can be separated into an odd and an even mode, and that the weakly nonlinear interaction between these modes determines whether the droplet climbs up or slides down the plane, consistent with earlier work in the limit of small contact angles (Benilov and Billingham, J. Fluid Mech. vol. 674, 2011, pp. 93–119). In this weakly nonlinear limit, we find that, as the static contact angle approaches $\unicode[STIX]{x03C0}$ (the non-wetting limit), the rise velocity of the droplet (specifically the velocity of the droplet averaged over one period of the motion) becomes a highly oscillatory function of static contact angle due to a high frequency mode that is excited by the forcing. We also solve the full nonlinear moving boundary problem numerically using a boundary integral method. We use this to study the effect of contact angle hysteresis, which we find can increase the rise velocity of the droplet, provided that it is not so large as to completely fix the contact lines. We also study a time-dependent modification of the contact line law in an attempt to reproduce the unsteady contact line dynamics observed in experiments, where the apparent contact angle is not a single-valued function of contact line velocity. After adding lag into the contact line model, we find that the rise velocity of the droplet is significantly affected, and that larger rise velocities are possible.

CHARACTERIZATION OF DYNAMIC WETTING OF PLASMA-TREATED PTFE FILM

2007 ◽  
Vol 14 (04) ◽  
pp. 821-825 ◽  
Author(s):  
Q. F. WEI ◽  
Y. LIU ◽  
F. L. HUANG ◽  
S. H. HONG
Keyword(s):  
Contact Angle ◽  
Plasma Treatment ◽  
Surface Properties ◽  
Contact Angle Hysteresis ◽  
Frictional Coefficient ◽  
Dynamic Contact Angle ◽  
Contact Angles ◽  
Dynamic Wetting ◽  
Ptfe Film ◽  
Receding Contact

Polytetrafluoroethylene (PTFE) has been increasingly used in many industries due to its low frictional coefficient and excellent chemical inertness. The surface properties of PTFE are of importance in various applications. The surface properties of PTFE can be modified by different techniques. In this study, PTFE film was treated in oxygen plasma for improving surface wettability. The effects of plasma treatment on dynamic wetting behavior were characterized using Scanning Probe Microscopy (SPM), Fourier transform infrared spectroscopy (FTIR), and dynamic contact angle (DCA) measurements. SPM observations revealed the etching effect of the plasma treatment on the film. The introduction of hydrophilic groups by plasma treatment was detected by FTIR. The roughened and functionalized surface resulted in the change in both advancing and receding contact angles. Advancing and receding contact angles were significantly reduced, but the contact angle hysteresis was obviously increased after plasma treatment.

Adhesion force and Nanotribological Characteristics of Chemical Vapor Deposited Fluorocarbon Films

2003 ◽  
Vol 782 ◽  
Author(s):  
Nam-Kyun Kim ◽  
Tae-Gon Kim ◽  
Jin-Goo Park ◽  
Woon-Bae Kim ◽  
Hyung- Jae Shin
Keyword(s):  
Contact Angle ◽  
Adhesion Force ◽  
Contact Angle Hysteresis ◽  
Chemical Vapor ◽  
Surface Heterogeneity ◽  
Contact Angles ◽  
Fluorocarbon Films ◽  
Chemical Vapor Deposited ◽  
Infra Red ◽  
Coated Surfaces

ABSTRACTIn this study, Adhesion force and Nanotribological Characteristics of fluorocarbon (FC) films on Al deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) were evaluated. The contact angle of FC thin films on Al was measured to be around 110°. The surface energy was calculated to be 15 dynes/cm from the measurements of contact angles of polar and nonpolar solutions on surfaces. The contact angle hysteresis, which is an indicator for the surface heterogeneity, was lower than 30°. The friction force of FC films coated surfaces was three times lower than bare Al. The adhesion force of bare Al was measured to be around 9.6nN. The presence of FC films on Al reduced it to below 4nN. Fourier transform infra-red (FTIR) spectra showed the presence of fluorocarbon groups such as –CFn- and =CF=CF2.

Contact-angle hysteresis induced by pulmonary surfactants

1983 ◽  
Vol 54 (2) ◽  
pp. 420-426 ◽  
Author(s):  
B. A. Hills
Keyword(s):  
Contact Angle ◽  
Pulmonary Surfactant ◽  
Contact Angle Hysteresis ◽  
Hysteresis Loops ◽  
Contact Angles ◽  
Published Data ◽  
Hydrophilic Surfaces ◽  
Glass Slides ◽  
Dipalmitoyl Lecithin ◽  
Receding Contact

Hydrophilic surfaces in the form of glass slides have been coated with monolayers of three of the major components of pulmonary surfactant, and the wettabilities of the resulting surfaces have been studied by applying a single drop of saline. As fluid was added and removed over successive cycles, there was much hysteresis between the contact angle measured by a goniometer and the location of the triple point. All three surfactants, especially dipalmitoyl lecithin, were found to impart antiwetting properties, with maximum (advancing) contact angles sometimes exceeding 90 degrees and minimum (receding) contact angles seldom less than 28 degrees. In all cases (216 cycles on 36 films) fluid receded to expose the dry subphase. The hysteresis loops agree well with a similar loop calculated from published data for a cat lung in which the pressure-volume cycle has been established for both liquid and air inflation. Contact-angle hysteresis is offered as a possible alternative to surface tension as the surface parameter primarily responsible for the interfacial contribution to compliance hysteresis in the excised lung.

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