Name: preparation and high-temperature anti-adhesion behavior of a slippery surface on stainless steel
Uploaded: 2018-03-29T12:30:00.000+00:00
Duration: 10 min 52 s
Description: Watch this Scientific Journal Video about Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel at JoVE.com

This work was supported by the National Natural Science Foundation of China (Grant No. 51290292) and was also supported by the Academic Excellence Foundation of BUAA for PhD students.

1. Photolithography on Stainless Steel
<ol>
	<li>Design the photomask using a mechanical drawing software and fabricate the design by submitting it to a photomask printer4.</li>
	<li>Wash the stainless steel (316 SS; lengthx width: 4 cm x 4 cm, thickness: 1 mm) by rinsing it in alkaline solutions (50 g/L NaOH and 40 g/L Na2CO3) at room temperature for 15 min to remove oil contaminants.</li>
	<li>Thoroughly clean the stainless steel by performing ultrasonic cleaning in an ultrasonic cleaning machine (working frequency: 40 KHz, ultrasonic power: 500 W). Rinse it sequentially with deionized water, n-hexane, acetone, and ethanol for 10 min each.</li>
	<li>Dry the stainless steel by placing it on a hot plate at 150 &#176;C for 30 min. Protect the stainless steel by covering it with a sheet of aluminum (Al) foil.</li>
	<li>Place the stainless steel on the center of a spin coater. Use a dropper to deposit positive photoresist (about 1 mL) onto the stainless steel, from the center to the edge, until the photoresist completely covers the stainless steel. Avoid bubble formation in the photoresist.
	<ol>
		<li>Perform spin-coating, first with a speed of 700 rpm/min for 6 s, to start the spin cycle, and then with a speed of 1,500 rpm/min for 15 s, to evenly spread the photoresist.</li>
	</ol>
	</li>
	<li>Release the vacuum valve and retrieve the stainless steel using a pair of tweezers. Place the stainless steel on a hot plate at 120 &#176;C for 2 min to bake the photoresist.</li>
	<li>Place the stainless steel on the vacuum valve of a photolithography machine. Set the exposure time of the photolithography machine to 25 s. 
	NOTE: Here, the photolithography machine is a contact aligner with an ultraviolet (UV) light wavelength of 254 nm and a light intensity of 13 mW/cm2.</li>
	<li>Release the stainless steel and place it in the developer solution for 1 min to remove the photoresist without exposing it to the UV light. Remove the stainless steel from the developer solution, wash it with deionized water, and dry it under N2 gas.</li>
	<li>Place the stainless steel on a hot plate to bake at 120 &#176;C for 2 min.</li>
	<li>Use an upright microscope with a magnification of 100x to observe the surface of the stainless steel to inspect the obtained photoresist texture.</li>
</ol>
2. Chemical Etching of Stainless Steel
<ol>
	<li>Prepare a chemical etching solution with a volume of 200 mL (400 g/L FeCl3, 20 g/L phosphoric acid, and 100 g/L hydrochloric acid) in a 500-mL beaker.</li>
	<li>Place the stainless steel with photoresist texture in the chemical solution for 10 min. Do not allow the stainless-steel pieces to contact each other. Place a maximum of four stainless steel pieces at one time.</li>
	<li>Take out of the chemically etched stainless steel using tweezers, wash the pieces with deionized water for 1 min, and dry them with N2 gas.</li>
	<li>Remove the photoresist texture by submerging the stainless steel in acetone for ultrasonic cleaning for 5 min. Then, dry the chemically etched stainless steel with N2 gas.</li>
</ol>
3. OTS Self-assembly on Chemically Etched Stainless Steel
<ol>
	<li>Clean the chemically etched stainless steel with a steady stream of deionized water, dry it with N2 gas, and place it on a hot plate at 100 &#176;C for 30 min to completely dry the surface.</li>
	<li>Hydroxylate the chemically etched stainless steel with an O2 plasma treatment in an RF plasma machine, with an RF power of 100 W for 10 min, a system pressure of 100 mbar, and a flow rate of 20 sccm.</li>
	<li>Prepare 1 mM OTS solution in anhydrous toluene in a beaker. Dry the beaker thoroughly before solution preparation.</li>
	<li>Rinse the chemically etched stainless steel with the OTS solution for 4 h at room temperature. Place the beaker in a sealed bag. Do not allow the stainless steel pieces to contact each other.</li>
	<li>Remove the stainless steel, clean it with anhydrous toluene by performing ultrasonic cleaning for 10 min, and dry it with N2 gas.</li>
</ol>
4. Slippery Surface Preparation
<ol>
	<li>Deposit approximately 10 mL/cm2 silicone oil (viscosity: 350 cst; surface tension: 21.1 mN/m) onto the OTS-coated, chemically etched stainless steel using a dropper.</li>
	<li>Use an optical stereomicroscope to observe the wetting process of the silicone oil on the stainless-steel surface (magnification of 10x).</li>
	<li>Remove the excess silicone oil by placing the stainless steel in a vertical position for 1 h.</li>
</ol>
5. Investigation of Water Sliding Behavior on Slippery Surfaces
<ol>
	<li>Deposit a 4-&#181;L water droplet on the slippery surface. Place the stainless steel under an optical microscope and tilt the substrate by ~2&#176;.</li>
	<li>Visualize the water droplet sliding on the slippery surface at a low magnification (50x) to check that the slippery surface has the easy sliding property.</li>
</ol>
6. Analysis of Anti-wetting on the Slippery Surface at High Temperatures
<ol>
	<li>Place the stainless steel with a slippery surface on a hot plate using tweezers. Set the hot plate at different high temperatures (i.e., 200 &#176;C, 250 &#176;C, and 300 &#176;C) to analyze the anti-wetting behaviors at different temperatures. 
	NOTE: Do not directly touch the high-temperature stainless steel with hands.</li>
	<li>Use a micro-syringe to deposit a 10-&#181;L water droplet on the slippery surface. 
	NOTE: Before dropping the water droplet, the temperature of the slippery surface should reach equilibrium.</li>
	<li>Use a high-speed camera to record the water droplet movement at a frame rate of 500 Hz.
	<ol>
		<li>Fix the camera to a tripod and direct the lens of the camera toward the stainless steel. Adjust the focus of the camera to obtain a clear water droplet image. Record the movement of the water droplet on the stainless-steel surface by pushing the start button of the camera. Push the end button of the camera when the water droplet slides off the stainless steel to complete the recording.</li>
	</ol>
	</li>
</ol>
7. Analysis of the Anti-adhesion Effects of the Slippery Surface on Soft Tissue
<ol>
	<li>Use a manipulator, a dynamometer, a hot plate, and a stationary fixture to set up an adhesion force measurement platform4, as shown in Figure 3a.</li>
	<li>Place the test surface on the hot plate. Use a clamp to fix the stainless steel on the plate. Heat the test surface to a certain high temperature (e.g., 300 &#176;C). 
	NOTE: The test surface should closely contact the hot plate to ensure efficient heat transport to the slippery surface.</li>
	<li>Fix the dynamometer to the manipulator. Connect a cylinder table (diameter: 2 cm) with a force head to act as a soft tissue fixed platform.</li>
	<li>Fix the soft tissue (e.g., chicken breast; length: 5 cm, width: 2 cm, thickness: 3 mm) onto the cylinder table using a thin wire. Ensure that the soft tissue surface is approximately even.</li>
	<li>Load the soft tissue onto the test surface at a speed of 1 mm/s until the dynamometer reaches a certain maximum force (e.g., 4.5 N) by rotating the motion button of the manipulator. Then, unload the soft tissue at the same speed.</li>
	<li>Connect a computer to the dynamometer using a data transmission line and record the real-time force between the soft tissue and the test surface.</li>
</ol>

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The authors have nothing to disclose.

This manuscript details protocols for fabricating a slippery surface with high-temperature resistance. The slippery property of our prepared surface was demonstrated by observing the easy-sliding behavior of a water droplet. Then, the anti-wetting of the prepared slippery surface at different high temperatures was investigated by depositing a water droplet on the hot surface. The results show that the prepared slippery surface maintained its slippery property even when it was heated to above 300 &#176;C. We also determin...

Anti-adhesion surfaces at high temperatures for use with liquids and soft tissues have received considerable interest because of their extensive application potential in electrosurgical instruments, engines, pipelines etc.1,2,3,4. Bioinspired surfaces, particularly superhydrophobic surfaces, are considered the ideal choice because of their excellent anti-wetting abilities and self-cleaning properties5. In superhydrophobic surfaces, the anti-wetting ability should be ascribed to the locked air in the surface structure. However, the superhydrophobic state is unstable because it is in the Cassie-Baxter state6,7. Also, at high temperatures, the anti-wetting for liquid droplets can fail because of the wetting state transition from the Cassie-Baxter to the Wenzel state8. This wetting transition is induced by small liquid droplet wetting in the structures, which results in the failure to lock the air in place.
Recently, inspired by the slippery properties of the peritome of the pitcher plant, Nepenthes, Wong et al. reported a concept to construct slippery surfaces by infusing a lubricant into the surface structures9,10,11. Due to capillary force, the structures can firmly hold the lubricant in place, just as in the locked air pocket on superhydrophobic surfaces. Thus, the lubricant and surface structures can form a stable solid/liquid surface. When the lubricant has a preferential affinity for the surface structure, the liquid droplet on the composite surface can slide easily, with only a very low contact angle hysteresis (e.g., ~2&#176;)12. This lubricant layer also enables the surface to have remarkable anti-wetting capabilities13, demonstrating great potential for medical devices14,15. However, previous studies on slippery surfaces mainly focused on the preparation for application at room temperature or low temperatures. There are very few studies on the preparation of slippery surfaces with high-temperature resistance. For example, Zhang et al. showed that the rapid evaporation of lubricant rapidly causes the failure of the slippery property at even slightly high temperatures16.
Slippery surfaces with high-temperature resistance can widen the application potential; for example, they can be used as liquid barriers to decrease soft tissue adhesion to electrosurgical instrument tips. During the surgical operation, severe soft tissue adhesion occurs because of the high temperature of the electrosurgical instrument tips. The soft tissue can be charred, causing it to adhere to the instrument tip, which then tears the soft tissue around the tip17,18,19. The adhered soft tissue on the electrosurgical instrument tip negatively influences the operation and also may induce the failure of hemostasis19,20. These effects significantly harm people&#39;s health and economic interest. Therefore, solving the issue of soft tissue adhesion to electrosurgical instruments is very urgent. In fact, slippery surfaces offer an opportunity to solve this problem.
Here, we present a protocol to fabricate slippery surfaces available at high temperatures. Stainless steel was selected as the surface material because of its high-temperature resistance. The stainless steel was roughened by photolithography-assisted chemical etching. Then, the surface was functionalized with a biocompatible material, saline octadecyltrichlorosilane (OTS)21,22,23,24. A slippery surface was prepared by adding silicone oil. These materials enabled the slippery surface to achieve high-temperature resistance. The anti-wetting property at high temperatures and the anti-adhesion effects on soft tissue were investigated. The results show the potential of using slippery surfaces to solve the anti-adhesion problem at high temperatures.

<table><tbody><tr><td>Stainless steel</td><td>Hongtu Corporation</td><td>316</td><td>Use as received</td></tr><tr><td>Octadecyltrichlorosilane</td><td>Huaxia Reagent</td><td>112-04-9</td><td>Use as received</td></tr><tr><td>Photoresist</td><td>Kempur Microelectronic Corporation</td><td>317S</td><td>Use as received</td></tr><tr><td>Silicone oil</td><td>Beijing Chemical Works</td><td>350 cst</td><td>Use as received</td></tr><tr><td>Anhydrous toluene</td><td>Beijing Chemical Works</td><td>108-88-3</td><td>Use as received</td></tr><tr><td>Phosphoric acid (H&lt;span class=&quot;font7&quot;&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/span&gt;&lt;span class=&quot;font0&quot;&gt;PO&lt;/span&gt;&lt;span class=&quot;font7&quot;&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;/span&gt;&lt;span class=&quot;font0&quot;&gt;)&lt;/span&gt;</td><td>Tianjin Chemical Corporation</td><td>7664-38-2</td><td>Use as received</td></tr><tr><td>Hydrochloric acid (HCl)</td><td>Tianjin Chemical Corporation</td><td>7647-01-0</td><td>Use as received</td></tr><tr><td>&lt;span class=&quot;font0&quot;&gt;F&lt;/span&gt;&lt;span class=&quot;font8&quot;&gt;erric chloride (&lt;/span&gt;&lt;span class=&quot;font0&quot;&gt;FeCl&lt;/span&gt;&lt;span class=&quot;font7&quot;&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/span&gt;&lt;span class=&quot;font8&quot;&gt;)&lt;/span&gt;</td><td>Tianjin Chemical Corporation</td><td>7705-08-0</td><td>Use as received</td></tr><tr><td>Optical upright microscope</td><td>Olympus</td><td>BX51</td><td></td></tr><tr><td>Optical stereo microscope</td><td>Olympus</td><td>SZX16</td><td></td></tr><tr><td>High speed camera</td><td>Olympus</td><td>i-SPEED LT</td><td></td></tr><tr><td>Ultrasonic cleaner</td><td>KUNSHAN ULTRASONIC INSTRUMENTS CO. LTD</td><td>KQ-500E</td><td></td></tr><tr><td>Dynamometer</td><td>Yueqing Handapi Instruments Co. Ltd</td><td>HP-5</td><td></td></tr><tr><td>Manipulator</td><td>Yueqing Handapi Instruments Co. Ltd</td><td>HLD</td><td></td></tr><tr><td>Hot plate</td><td>Shenzhen Jingyihuang Corporation</td><td>DRB-1</td><td></td></tr></tbody></table>

preparation and high-temperature anti-adhesion behavior of a slippery surface on stainless steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

The slippery surface was prepared by adding silicone oil to OTS-coated, chemically etched stainless steel. Due to their similar chemical properties, the surface was completely wetted by silicone oil. The wetting process is shown in Figure 1a. The red dotted line marks the wetting line. After the wetting, a visible oil layer could be distinguished from the dry surface. The slippery property of the prepared slippery surface was investigated by depositing a wate...

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Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

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7.5K Views.  Beihang University. Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

Video: Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

A protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. Procedures and examples to determine the adhesion force and free energy of these molecules on solid supports and bio-interfaces are provided.

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single ...

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Chemistry

The Evolution of Silica Nanoparticle-polyester Coatings on Surfaces Exposed to Sunlight

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, building and food industries, amongst others. Polyester and coatings containing both polyester and silica nanoparticles (SiO2NPs) have been widely used to protect steel substrata from corrosion. In this study, we utilized X-ray photoelectron spectroscopy, attenuated total reflection infrared micro-spectroscopy, water contact angle measurements, optical profiling and atomic force microscopy to provide an insight into how exposure to sunlight can cause changes in the micro- and nanoscale integrity of the coatings. No significant change in surface micro-topography was detected using optical profilometry, however, statistically significant nanoscale changes to the surface were detected using atomic force microscopy. Analysis of the X-ray photoelectron spectroscopy and attenuated total reflection infrared micro-spectroscopy data revealed that degradation of the ester groups had occurred through exposure to ultraviolet light to form COO&#903;, -H2C&#903;, -O&#903;, -CO&#903; radicals. During the degradation process, CO and CO2 were also produced.

Two types of surfaces, polyester-coated steel and polyester coated with a layer of silica nanoparticles, were studied. Both surfaces were exposed to sunlight, which was found to cause substantial changes in the chemistry and nanoscale topography of the surface.

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, ...

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 and a superhydrophobic agent were coated on the HGM surface in one step. TBT and PFOTES were selected as the Ti source and the superhydrophobic agent, respectively. They were both coated on the HGM, and after the hydrothermal process, the TBT turned to anatase TiO2. In this way, a PFOTES/TiO2-coated HGM (MCHGM) was prepared. For comparison, PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The PFOTES and TiO2 coatings on the HGM surface were demonstrated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive detector (EDS) characterizations. The MCHGM showed a higher contact angle (153&#176;) but a lower sliding angle (16&#176;) than F-SCHGM, with a contact angle of 141.2&#176; and a sliding angle of 67&#176;. In addition, both Ti-SCHGM and MCHGM displayed similar IR reflectivity values, which were about 5.8% higher than the original HGM and F-SCHGM. Also, the PFOTES coating barely changed the thermal conductivity. Therefore, F-SCHGM, with a thermal conductivity of 0.0479 W/(m&#183;K), was quite like the original HGM, which was 0.0475 W/(m&#183;K). MCHGM and Ti-SCHGM were also similar. Their thermal conductivity values were 0.0543 W/(m&#183;K) and 0.0543 W/(m&#183;K), respectively. The TiO2 coating slightly increased the thermal conductivity, but with the increase in reflectivity, the overall heat-insulation property was enhanced. Finally, since the IR-reflecting property is provided by the HGM coating, if the coating is fouled, the reflectivity decreases. Therefore, with the superhydrophobic coating, the surface is protected from fouling, and its lifetime is also prolonged.

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to synthesize superhydrophobic, TiO2-coated hollow glass microspheres (HGM) with high IR-reflective properties.

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 ...

Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns

In this study, pool-boiling heat-transfer experiments were performed to investigate the effect of the number of interlines and the orientation of the hybrid wettable pattern. Hybrid wettable patterns were produced by coating superhydrophilic SiO2 on a masked, hydrophobic, cylindrical copper surface. Using de-ionized (DI) water as the working fluid, pool-boiling heat-transfer studies were conducted on the different surface-treated copper cylinders of a 25-mm diameter and a 40-mm length. The experimental results showed that the number of interlines and the orientation of the hybrid wettable pattern influenced the wall superheat and the HTC. By increasing the number of interlines, the HTC was enhanced when compared to the plain surface. Images obtained from the charge-coupled device (CCD) camera indicated that more bubbles formed on the interlines as compared to other parts. The hybrid wettable pattern with the lowermost section being hydrophobic gave the best heat-transfer coefficient (HTC). The experimental results indicated that the bubble dynamics of the surface is an important factor that determines the nucleate boiling.

Pool-boiling heat-transfer experiments were carried out to observe the effects of hybrid wettable patterns on the heat-transfer coefficient (HTC). The parameters of investigation are the number of interlines and the pattern orientation of the modified wettable surface.

In this study, pool-boiling heat-transfer experiments were performed to investigate the effect of the number of interlines and the orientation of the ...

Failure of Cleaning Verification in Pharmaceutical Industry Due to Uncleanliness of Stainless Steel Surface

The aim of this work is to identify the parameters that affect the recovery of pharmaceutical residues from the surface of stainless steel coupons. A series of factors were assessed, including drug product spike levels, spiking procedure, drug-excipient ratios, analyst-to-analyst variability, intraday variability, and cleaning procedure of the coupons. The lack of a well-defined procedure that consistently cleaned the coupon surface was identified as the major contributor to low and variable recoveries. Assessment of cleaning the surface of the coupons with clean-in-place solutions (CIP) gave high recovery (&#62;90%) and reproducible results (Srel&#8804;4%) regardless of the conditions that were assessed previously. The approach was successfully applied for cleaning verification of small molecules (MW &#60;1,000 Da) as well as large biomolecules (MW up to 50,000 Da).

The lack of a well-defined procedure that consistently cleaned coupon surfaces was identified as the major contributor to low and variable recoveries in cleaning verification. This manuscript describes the correct protocol of cleaning stainless steel coupons.

The aim of this work is to identify the parameters that affect the recovery of pharmaceutical residues from the surface of stainless steel coupons. A ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...

Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, batteries, and biomedical devices, etc., impose great challenges on the reliable performance of alloys exposed to extreme conditions where mechanical and electrochemical attack co-exist. Finding ways for alloys to mitigate the combined attack of wear and corrosion (i.e., tribocorrosion) under such extreme conditions is thus highly critical for improving their reliability and service lifetime when used in such conditions. The challenge lies in the fact that wear and corrosion are not independent of each other, but rather work synergistically to accelerate the total material loss. Thus, a reliable method to evaluate the tribocorrosion resistance of metals and alloys is needed. Here, a protocol for measuring the tribocorrosion rate and wear-corrosion synergy of Al-based bulk and thin film samples in a corrosive environment under room temperature is presented.

Here, we present a protocol to measure the tribocorrosion rate and wear-corrosion synergy of thin film and bulk Al alloys in simulated sea water at room temperature.

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, ...

Micromechanical Tension Testing of Additively Manufactured 17-4 PH Stainless Steel Specimens

This study presents a methodology for the rapid fabrication and micro-tensile testing of additively manufactured (AM) 17-4PH stainless steels by combining photolithography, wet-etching, focused ion beam (FIB) milling, and modified nanoindentation. Detailed procedures for proper sample surface preparation, photo-resist placement, etchant preparation, and FIB sequencing are described herein to allow for high throughput (rapid) specimen fabrication from bulk AM 17-4PH stainless steel volumes. Additionally, procedures for the nano-indenter tip modification to allow tensile testing are presented and a representative micro specimen is fabricated and tested to failure in tension. Tensile-grip-to-specimen alignment and sample engagement were the main challenges of the micro-tensile testing; however, by reducing the indenter tip dimensions, alignment and engagement between the tensile grip and specimen were improved. Results from the representative micro-scale in situ SEM tensile test indicate a single slip plane specimen fracture (typical of a ductile single crystal failure), differing from macro-scale AM 17-4PH post-yield tensile behavior.

Presented here is a procedure for measuring fundamental material properties through micromechanical tension testing. Described are the methods for micro-tensile specimen fabrication (allowing rapid micro-specimen fabrication from bulk material volumes by combining photolithography, chemical etching, and focused ion beam milling), indenter tip modification, and micromechanical tension testing (including an example).

This study presents a methodology for the rapid fabrication and micro-tensile testing of additively manufactured (AM) 17-4PH stainless steels by combining ...

Mitigation of Blood Borne Cell Attachment to Metal Implants through CD47-Derived Peptide Immobilization

The key complications associated with bare metal stents and drug eluting stents are in-stent restenosis and late stent thrombosis, respectively. Thus, improving the biocompatibility of metal stents remains a significant challenge. The goal of this protocol is to describe a robust technique of metal surface modification by biologically active peptides to increase biocompatibility of blood contacting medical implants, including endovascular stents. CD47 is an immunological species-specific marker of self and has anti-inflammatory properties. Studies have shown that a 22 amino acid peptide corresponding to the Ig domain of CD47 in the extracellular region (pepCD47), has anti-inflammatory properties like the full-length protein. In vivo studies in rats, and ex vivo studies in rabbit and human blood experimental systems from our lab have demonstrated that pepCD47 immobilization on metals improves their biocompatibility by preventing inflammatory cell attachment and activation. This paper describes the step-by step protocol for the functionalization of metal surfaces and peptide attachment. The metal surfaces are modified using polyallylamine bisphosphate with latent thiol groups (PABT) followed by deprotection of thiols and amplification of thiol-reactive sites via reaction with polyethyleneimine installed with pyridyldithio groups (PEI-PDT). Finally, pepCD47, incorporating terminal cysteine residues connected to the core peptide sequence through a dual 8-amino-3,6-dioxa-octanoyl spacer, are attached to the metal surface via disulfide bonds. This methodology of peptide attachment to metal surface is efficient and relatively inexpensive and thus can be applied to improve biocompatibility of several metallic biomaterials.

Presented here is a protocol for appending peptide CD47 (pepCD47) to metal stents using polybisphosphonate chemistry. Functionalization of metal stents using pepCD47 prevents the attachment and activation of inflammatory cells thus improving their biocompatibility.

The key complications associated with bare metal stents and drug eluting stents are in-stent restenosis and late stent thrombosis, respectively. Thus, ...