Influence of super-hydrophobic silicone rubber substrate on the growth and differentiation of human lens epithelial cells.

Materials with low cell adhesion are advantageous for production of replacement intraocular lens (IOL) to prevent posterior capsular opacification (PCO). We evaluated the feasibility of compression molding for manufacture of silicone rubber with super-hydrophobic surface and low cell infiltrative characteristics compared to ordinary hydrophobic silicone rubber. Silicone specimens with complex surface topology (super-hydrophobic) or smooth surfaces (hydrophobic) were manufactured by vacuum deforming and molding. Contact angle, microscopic surface structure, and transparency were evaluated. Super-hydrophobic and smooth samples were compared for effects on proliferation, adhesion, and morphology of human lens epithelial cells (hLECs). Epithelial-mesenchymal transition (EMT) was examined by immunofluorescence expression of fibronectin (Fn), Alpha-smooth muscle actin (α-SMA), and vimentin. The surface contact angle of super-hydrophobic silicone was greater than that of smooth silicone (153.8° vs. 116°). The super-hydrophobic surface exhibited a micron-scale palisade structure under scanning electron microscopy (unit length, width, and height of 80, 25, and 25 µm, respectively). However, cell number per 50 × microscopic field on super-hydrophobic surfaces was markedly reduced 24 and 72 h post-seeding compared to smooth surfaces (p < 0.01). Cells were cuboidal or spherical after 72h on super-hydrophobic surfaces, and exhibited numerous surface microvilli with fluff-base polarity, while cells on smooth surfaces exhibited morphological characteristics of EMT. Expression levels of the α-SMA and vimentin were reduced on super-hydrophobic surfaces compared to smooth surfaces. Super-hydrophobic silicon inhibits proliferation, adhesion, and EMT of hLECs, properties that may prevent fibrosis following cataract surgery.

Flexible Switching Pressure Sensors with Fast Response and Less Bending-Sensitive Performance Applied to Pain-Perception-Mimetic Gloves.

A strategy is proposed herein for preparing a flexible switching piezoresistive pressure sensor, which has a bridge-like structure and inverted micropyramids (IMPs) on its lower conductive substrate. The sensor substrates were prepared by injection compression molding (an industrial manufacturing process) using thermoplastic polyurethane (TPU; an industrial grade polymer). The designed bridge-like structure enables the sensor to obtain a pressure threshold. The flexibility of upper and lower TPU substrates allows them to contact quickly when pressed, and so the sensor exhibits a fast response (as short as 2 ms) and can respond to both static force and dynamic force (up to 50 Hz frequency), which are prominent for the sensor made from TPU. The sensor exhibits less bending-sensitive performance, which is attributed to the conformality of the upper and lower substrates and lower strain on the lower substrate with the IMP under bending. The sensor can amplify signal response at the monitoring limit (the relative resistance change is up to 46%). It can achieve a higher sensitivity in different low-pressure ranges by changing the gap of the bridge-like structure. Moreover, the sensor can obviously and steadily respond to an additional very low pressure under preloading and exhibits good durability performance. As the sensor has a pressure threshold similar to the human pain perception process, a pain-perception-mimetic glove that can identify the external mechanical stimuli but reduces the interference of finger bending is prepared, displaying potential applications of the flexible switching sensor in intelligent wearable protectors.

Long-Lived T-Shaped Micropillars with Submicron-Villi on PP/POE Surfaces with Grinding-Enhanced Water Repellency Fabricated via Hot Compression Molding.

Superhydrophobic properties are derived from the roughness of the surface of micro/nanostructures and low-surface-energy materials. However, they are both easy to damage on superhydrophobic surfaces after mechanical abrasion in practical applications, resulting in the transition from the Cassie-Baxter state to the Wenzel state and even the loss of water repellency. In this work, the mechanical properties of polypropylene (PP) toughened with poly(ethylene-co-octene) (POE) were improved for the fabrication of long-lived T-shaped micropillars with submicron-villi on top by a combined method of compression molding and grinding. A universal testing machine was modified as equipment for the precise control of the traveling distance of specimens on sandpaper in precise. The PP/POE blend possessed high tensile strength of up to ∼23.84 MPa as well as elongation at break of ∼533.60%. The abrasive grains on sandpaper reshaped their surface morphologies from micropillars to T-shaped microstructures, on which the submicron-villi as secondary structures formed. The abraded microstructured PP/POE surface exhibited the highest contact angle of 154.4° and the most stable wetting state with a bouncing height of 7.68 mm (3.2 times the diameter of the 7-µL droplet) after a traveling distance of 1000 mm on 3000-grit sandpaper among the abraded and unabraded PP/POE surfaces.

Combined Approach of Compression Molding and Magnetic Attraction to Micropatterning of Magnetic Polydimethylsiloxane Composite Surfaces with Excellent Anti-Icing/Deicing Performance.

The accumulation of ice and contaminants on the surface of composite insulators will cause high energy consumption or even major hazards to power systems. In this work, the polydimethylsiloxane (PDMS) silicone rubber was modified by surface micropatterning and material compositing. Highly crosslinked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) was used to directly coat ferroferric oxide (Fe3O4) nanoparticles. The obtained core-shell Fe3O4@PZS microspheres were loaded with carbon nanotubes (CNTs) to get CNTs/Fe3O4@PZS as the photothermal magnetic filler. The PDMS/CNTs/Fe3O4@PZS surfaces with micronscale truncated cones were prepared via a combined method of compression molding and magnetic attraction. The 1H,1H,2H,2H-perfluorodecyltrichlorosilane-coated template and magnetic field can increase the height of the microstructure to ∼76 µm and maintain the contact angle of microstructured PDMS/CNTs/Fe3O4@PZS surfaces at a high level (∼152°). Compared with the flat PDMS surface, the micronscale truncated cones extend the freezing time from 4.5 to 11.5 min and also undermine the ice adhesion strength from ∼25 to ∼17 kPa for the microstructured PDMS/CNTs/Fe3O4@PZS surface. The temperature of the PDMS/CNTs/Fe3O4@PZS surface molded with magnetic attraction increases linearly with time and the internal magnetic fillers and achieves 280 °C in 10 s. The efficiency of temperature rise is increased by ∼46%, and hence the entire frozen water droplet can melt within 20 s. The strategy combining active deicing with passive anti-icing undoubtedly promotes the development of high efficiency anti-icing materials and can be applied on insulators to prevent icing flashover.

Superhydrophobic SiC/CNTs Coatings with Photothermal Deicing and Passive Anti-Icing Properties.

For faster and greener anti-icing/deicing, a new generation of anti-icing materials are expected to possess both passive anti-icing properties and active deicing properties. The photothermal effect of carbon nanotubes (CNTs) is used in the field of photothermal cancer therapy, while the application in anti-icing/deicing is seldom investigated. Superhydrophobic SiC/CNTs coatings with photothermal deicing and passive anti-icing properties were first prepared by a simple spray-coating method. The results of 3D profile and microstructure observed via scanning electron microscopy demonstrate that the micronanostructure combined with peaklike SiC microstructure and villiform CNTs nanostructure makes the coatings surface superhydrophobic, exhibiting a water contact angle of up to 161° and a roll angle as low as 2°. This micronanostructure can also reduce ice anchoring and ice adhesion strength. Utilizing the photothermal effect of CNTs, the surface temperature of the coatings is rapidly increased upon near-infrared light (808 nm) irradiation. The heat is transferred rapidly to the surroundings by highly thermal conductive CNTs. The light-to-heat conversion efficiency in deicing tests is approximately 50.94%, achieving a highly efficient remote deicing effect. This superhydrophobic coating combining photothermal deicing and passive anti-icing properties is expected to be further used in various practical applications and in development of a new generation of anti-icing/deicing coatings.

Rapid fabrication of bio-inspired nanostructure with hydrophobicity and antireflectivity on polystyrene surface replicating from cicada wings.

The fine nanostructure on the cicada wing of Cryptotympana atrata fabricius, which exhibits hydrophobicity and antireflectivity, is carefully examined. A promising strategy is proposed for facilely and successively replicating the natural functional nanostructure of the cicada wing onto polystyrene (PS) surfaces. First, a nickel replica with tapered nanopores is fabricated by combining electroless plating and subsequent electroplating with the natural cicada wing as an original template. Then, using microinjection compression molding, with the nickel replica as a template, the tapered nanopores are transcribed onto the PS surface, resulting in orderly and densely arranged nanopillars with a mean diameter of about 156 nm and a mean pitch of about 180 nm. The natural cicada wing and fabricated nickel replica are reusable. Interestingly, the PS replica surface exhibits a water contact angle of 143° ± 2° and a reflectance of about 4% in the wavelength range of 400-1000 nm. These results mean that the bionic PS replica not only inherits the nanostructure of the natural wing, but also its hydrophobic and antireflective properties. The mechanisms for the hydrophobic and antireflective properties are revealed via composite wetting interface and effective medium layer on the replica surface, respectively. The proposed fast and efficient replication strategy can be an excellent candidate for mimicking bio-inspired functional micro/nanostructures without complicated procedures and expensive materials.

Controlling Superwettability by Microstructure and Surface Energy Manipulation on Three-Dimensional Substrates for Versatile Gravity-Driven Oil/Water Separation.

Superwettable materials have gained tremendous attention because of their special wetting abilities. The key to obtaining and tuning superwettability is to precisely control the interfacial microstructures and surface energies of materials. Herein, we propose a novel approach to controlling the superwettability of three-dimensional foams. The surface microstructure was manipulated by the layer-by-layer covalent grafting of multidimensional nanoparticles (e.g., silica, carbon nanotubes, and graphene oxide), and the surface energy was tailored by grafting chemicals with different functional groups. This grafting approach improved the mechanical performance, reduced particle loading, and prevented particle disassociation, thereby increasing the absorption capacity and durability of the functionalized foams. More importantly, superhydrophobic/superoleophilic foams were obtained after heptanol grafting. They showed water contact angles of 153° in air and 158° in oil, an absorption capacity 113 times their weight gain, and a remarkable flux of 32.6 L m-2 s-1 for the separation of oil from water driven by gravity. Polydopamine grafting resulted in superhydrophilic/underwater superoleophobic foams that had an oil contact angle of 152° under water and a high flux of 19.3 L m-2 s-1 for the separation of water from oil. Thus, this study offers not only intelligent materials for versatile oil/water separation but also a profound approach for engineering high-performance superwettable materials.

Shape memory thermoplastic polyurethane (TPU)/poly(ε-caprolactone) (PCL) blends as self-knotting sutures.

Thermally responsive shape memory polymers have promising applications in many fields, especially in biomedical areas. In this study, a simple method was purposed to prepare thermoplastic polyurethane (TPU)/poly(ε-caprolactone) (PCL) blends that possess shape memory attributes. TPU and PCL were melt compounded via a twin-screw extruder and injection molded at various ratios. Multiple test methods were used to characterize their shape memory properties and reveal the underling mechanism. The blends containing 25% TPU and 75% PCL possessed the best shape memory properties as indicated by a 98% shape fixing ratio and 90% shape recovery ratio. This was attributed to the hybrid crystalline and amorphous regions of PCL and TPU. We also found that PCL and TPU had good miscibility and that the PCL domain in TPU25% had higher crystallinity than neat PCL. The crystalline region in TPU25% could deform and maintain its temporary shape when stretched, which contributed to its high shape fixing attribute, while the rubbery TPU region assisted in the recovery of the sample upon heating by releasing the deformation energy stored. Moreover, the TPU25% string prepared could knot itself in a hot water bath, indicating a potential for suture applications. Lastly, the 3T3 fibroblast cells cultured on the TPU/PCL blends showed high viability and active substrate-cell interactions.