Rubbing Treatment Research Articles

Investigation of orientation behavior of nematic liquid crystals on UV-irradiated polyimide films

Abstract The orientation mechanism of liquid crystals (LCs) on surfaces remains unclear, despite several methods for controlling pretilt angles. This study investigates the relationship between the surface condition of polyimide films, whose pretilt angles can be controlled by UV dose, and LC orientation behavior. Absorbance at wavelength of 200 nm and 260 nm significantly decrease, while thickness reduces approximately 4 nm. A rubbing treatment further decreases the thickness by approximately 2 nm. Atomic force microscopy confirmed the change in molecular conformation by UV-irradiation and rubbing treatment. The dispersive and polar components of the surface free energy of UV-irradiated polyimide films are evaluated, it’s found that only the polar component changes with UV dose. Additionally, we confirm that the alignment of LCs transitions from homeotropic to planar with increased UV irradiation, demonstrating that pretilt angle distribution can be spatially controlled. These results contribute to establishing a photoalignment method for pretilt angle control.

Self-Assembly of Cyclic-Bending Collagen Fibrils by Polyimide Films.

The cyclic-bending morphologies of the fibrils formed by the self-assembly of type I collagen (Col) are closely related to the mechanisms of various diseases. Therefore, studies that allow the self-assembly of Col molecules to form cyclic-bending fibrils in vitro are vitally important. In this study, we successfully achieved the cyclic-bending shapes (specifically, a regular hexagonal shape) of Col molecules by controlling the steric structures of polyimide (PI) molecular chains through the film formation process. Specifically, when a single layer of PI film was baked, the PI molecular chains within the film bent in the direction parallel to the substrate surface plane. Repeating the layering and baking processes resulted in 3D structures of the PI molecular chains, which were oriented in the direction perpendicular to the substrate surface plane. This three-dimensional bending would result from the PI molecular chain interactions between the upper and lower layers. When the Col molecules were reacted on these film surfaces, they recognized the structures of the PI molecular chains and self-assembled to form cyclic-bending Col fibrils. Especially, in PI films subjected to three cycles of layering and baking, hemicircular-shaped Col fibrils were observed to be regularly arrayed. Additionally, these regularly cyclic-bending fibrils were aligned in the uniaxial direction through a uniaxial rubbing treatment of the PI films. This successful research is significant both as a method for controlling the morphologies of Col fibrils and as a study that explores the biomedical implications of Col fibril cyclic-bending in the living body.

Durability of photocatalytic ZnO-based surface coatings and preservation of their antibacterial effect after simulated wear

This study focused on antibacterial durability testing of surface coatings based on acrylic matrix-embedded UVA-activated ZnO. Such coatings on stainless steel were treated by dry rubbing, wet rubbing, and abrasive treatment to simulate wearing during everyday touching, cleaning, and aggressive scrubbing. Abrasive treatment caused clear topological changes to the surfaces, flattened the surface at the micrometer scale, and released a significant amount of surface material, which was partly acrylic matrix and partly the embedded ZnO. The highest release of Zn, the most prominent photocatalytic activity under UVA and the greatest antibacterial effect, was observed for abrasively treated surfaces. Although a small amount of surface material was released from surfaces after dry and wet rubbing, no significant increase in Zn release or photocatalytic activity was detected. On the contrary, antibacterial activity after those treatments decreased in comparison with untreated surfaces, likely due to partial surface masking by the released acrylic matrix. In summary, our results indicate that antimicrobial ZnO material immobilized in acrylic matrix creates stable surface coatings that may lose some of their efficacy during daily use and cleaning procedures, but activity of which will be retained during a more aggressive abrasion procedure.

Multifunctional Al-doped ZnO thin films for vertically aligned liquid crystal devices

The integration of ITO-free transparent conductive layers remains a big challenge for development of next generation technologies. Here, we demonstrate the feasibility of transparent and conductive Aluminum-doped Zinc Oxide (AZO) thin films to operate simultaneously as electrode and alignment layer in Liquid Crystal (LC) device configuration. Controlling the growth process of AZO thin films by Atomic Layer Deposition (ALD) technique results of predominantly (100) crystallographic oriented AZO with very high transparency and excellent conductivity. The exceptionally low surface free energy of (100) oriented AZO, along with the topological modification following the mechanical rubbing treatment were used to elucidate the mechanism of LC molecules alignment on the surface of AZO film. The uniform vertical orientation of the nematic LC director was confirmed by polarized optical microscopy and pretilt angle measurements. The competitive electro-optical performance in terms of phase modulation, threshold and saturation voltages and contrast ratio of the assembled LC device reveals the great potential of AZO thin films as transparent electrode and alignment layer for future LC display applications with versatile functionality.

Polarization-insensitive liquid crystal Fresnel lens based on self-assembly polymer gravels and chiral dopant.

A polarization-insensitive liquid crystal (LC) Fresnel lens is developed with binary LC configurations of 90°-twisted nematic (TN) and vertically-aligned (VA) domains in the adjacent zones. A LC mixture comprised of nematic host, photopolymer and chiral material is initially filled into the VA cell with orthogonal rubbing treatment. After the ultraviolet irradiation on the filled LC cell through a photomask with Fresnel zone plate pattern, the interactions among orthogonal rubbing treatment, self-assembly polymer gravels, and chiral material induce the 90°-TN structure in the odd zones, whereas the initial VA structures are maintained in the even zones. The fabricated LC Fresnel lens with binary configuration emerges a maximum diffraction efficiency of around 35% at a voltage of 2.3 V, close to the theoretical diffraction limit of around 41%. The diffractive focus of the LC Fresnel lens is polarization-insensitive at the voltage above 2 V. When the voltage reaches 10 V, the diffractive focus vanishes. The numerical calculation confirms that the polarization-insensitive property appears in the primary focus of the LC Fresnel lens. This work reports a simple method to develop a highly efficient, polarization-insensitive, and electrically tunable LC Fresnel lens which is favorable for imaging system.

Microstructure design of polyester industrial yarns with excellent flame retardancy and high strength

In order to solve the problem that it is difficult to balance the high strength and flame retardancy of polyester industrial yarn, the possibility of controlling the uniform dispersion of flame retardant without affecting the crystallization of polyester was discussed in this paper. The long-chain branched flame retardant with good thermal stability in the range of processing temperature was chosen to blend with high viscosity polyester. The addition of flame retardant reduced the melt viscosity and the crystallization ability of polyester, so the melt spinning and drawing process of the flame retardant polyester industrial yarn were optimized for the sufficient crystallization of polyester based on the rheological and crystallization properties of flame retardant polyester. Due to the steric effect of flame retardant, it was eliminated from the crystal region and only existed in the amorphous region of polyester. As a result, the microstructure with high crystallinity and orientation and the morphology with a uniform dispersion of flame retardant were obtained. The flame retardant high strength polyester industrial yarn was successfully prepared with a limiting oxygen index of 32.0% and a breaking strength of 8.0 cN/dtex, which meets the UL-94 V-0 standard and shows good durability of flame retardant after washing and rubbing treatment, achieving the goal of flame retardancy and high strength for the polyester industrial yarn.

Rehabilitation and Care Program for Pain during COVID-19 Recovery

For the COVID-19 outbreak, there are no specific drugs to treat or prevent patient deterioration and severe complications [1]. When the outbreak occurred, TCM methods gained valuable experience in the prevention and treatment of COVID-19 [2]. In the prevention and treatment of COVID-19, the results of several clinical trials show that TCM plays an important role in the prevention, treatment and rehabilitation of COVID-19 [3]. Many convalescent patients suffer with pain symptoms due to factors such as disease and complications [4]. Psychotherapy, sports rehabilitation, TCM external application, fumigation, rubbing, acupuncture and moxibustion treatment have formed a unique rehabilitation and nursing plan for COVID-19 convalescent pain, which plays an important role in alleviating the convalescent pain of COVID-19 patients [5].

Rehabilitation and care program for pain During COVID-19 recovery

Abstract: For the COVID-19 outbreak, there are no specific drugs to treat or prevent patient deterioration and severe complications[1]. When the outbreak occurred, TCM methods gained valuable experience in the prevention and treatment of C O V 1 D-19[2]. In the prevention and treatment of COVID-19, the results of several clinical trials show that TCM plays an important role in the prevention, treatment and rehabilitation of COVID-19[3]. Many convalescent patients suffer with pain symptoms due to factors such as disease and complications.Psychotherapy, sports rehabilitation, TCM external application, fumigation, rubbing, acupuncture and moxibustion treatment have formed a unique rehabilitation and nursing plan for COVID-19 convalescent pain, which plays an important role in alleviating the convalescent pain of COVID-19 patients.

Rubbing-free liquid crystal electro-optic device based on organic single-crystal rubrene.

Liquid crystals (LCs) have been a vital component of modern communication and photonic technologies. However, traditional LC alignment on polyimide (PI) requires mechanically rubbing treatment to control LC orientation, suffering from dust particles, surface damage, and electrostatic charges. In this paper, LC alignment on organic single-crystal rubrene (SCR) has been studied and used to fabricate rubbing-free LC devices. A rubrene/toluene solution is spin-coated on the indium-tin-oxide (ITO) substrate and transformed thereafter to the orthorhombic SCR after annealing. Experimental result reveals that SCR-based LC cell has a homogeneous alignment geometry, the pretilt angle of LCs is low and the orientation of LCs is determined with capillary filling action of LCs. LC alignment on SCR performs a wider thermal tolerance than that on PI by virtue of the strong anchoring nature of LCs on SCR due to van der Waals and π-π electron stacking interactions between the rubrene and LCs. SCR-based LC cell performs a lower operation voltage, faster response time, and higher voltage holding ratio than the traditional PI-based LC cell. Organic SCR enables to play a role as weakly conductive alignment layer without rubbing treatment and offers versatile function to develop novel LC devices.

Design and Synthesis of Self-Healable Superhydrophobic Coatings for Oil/Water Separation.

The introduction of the self-healing function into superhydrophobic surfaces has recently raised increasing attention because it can renew the feature of the surface iteratively to a large extent to extend the service life span of the surface in practical applications. However, it still faces a great challenge on how to achieve this unique surface with a tunable self-healing function via an easy and effective way. Here, we propose a general, yet easily implemented strategy to endow a diversity of commercial substrates with self-healable superhydrophobic surfaces mainly relying on the collective use of the polydopamine (PDA) chemistry with a hydrophobic silane-octadecyltrimethoxysilane (ODTMS). Upon applying ultrasonication for 30 min to an alkaline aqueous solution comprising dopamine hydrochloride (DA) and ODTMS, ODTMS disperses into the aqueous phase as microdroplets, while DA polymerizes into PDA exclusively onto the micro-sized oil droplets, forming capsules with nanoroughness. In the presence of substrates, PDA also anchors these composite capsules onto substrates, resulting in hierarchical surfaces. ODTMS is detected abundantly on the hierarchical surfaces, leading to superhydrophobic surfaces. Remarkably, this superhydrophobicity is self-restorable at room temperature (e.g., days) once it is deteriorated by the air plasma or extremely acid/alkali treatment, and this self-restoration can be significantly accelerated via the heating (2 h) or rubbing (5 min) treatment. Generally, heating and rubbing are the valid ways to induce self-healing, which is speculated to accelerate the migration of hidden ODTMS from the capsules to the surfaces because of the minimization of the global surface-free energy. Benefiting from the self-healing superhydrophobicity, we devise oil/water separation using various surface-modified commercial fabrics, which exhibit a prolonged life span in applications and may further facilitate other usage in environmental remediation and water purification.

Capillary Flows of Nematic Liquid Crystal

In this paper we report the new experimental results on the rise of a liquid crystal in flat capillaries with inner photosensitive surfaces. The capillaries with different surface orientations were prepared by the use of the photo-alignment technique. Such a surface treatment makes it possible to eliminate the noncontrollable influence of a nanorelief on the wetting process, which takes place in the rubbing treatment technique previously used in similar experiments. The dynamics of the capillary rise of a nematic liquid crystal 5CB (4-cyano-4′-pentylbiphenyl) in vertical plane capillaries with photo-aligned substrates were studied for the first time. It was found that the stationary value of a contact angle weakly depends on the direction of a planar surface orientation relative to the direction of a capillary rise. It has been shown that the application of strong electric fields resulted in a decreasing of the contact angle. The results, obtained for the nematic liquid crystal, are compared with the results of an investigation of the capillary flow in a shock-free ferroelectric smectic phase.

Influence of simulated grape crushing process on phenolic compounds extraction, astringency and color of Cabernet Sauvignon model wine

Phenolic compounds extracted from grapes play a decisive role on organoleptic properties of wine, especially wine astringency and color. In this study, the skins and seeds of Cabernet Sauvignon grape were implemented 4 physical treatments (tearing, shearing, rubbing and squeezing) to simulate mechanical damage caused by crusher or de-stemmer in the process of industrial wine production. Equivalent weight of treated grape skins (14.79%) or seeds (6.11%) separated from grapes were added into pre-prepared synthetic wine to simulate the maceration for 14 days to obtain the model wines. Polyphenolic components, astringency and color index as well as sensory evaluation of model wines were then analyzed. The results indicated that 4 physical treatments led to an increase of the mean degree of polymerization and percentage of galloylation of proanthocyanidin in model wines. A significant increase of b* value of model wine by the rubbing or squeezing treatment on both skins and seeds was detected, despite of no significant difference of total anthocyanin in skin model wines. The physical treated skins and seeds gave model wine a more effective capacity in precipitating proteins, indicating a stronger astringency potential, among which the rub treatment strengthened the most of astringency perceptions.

Novel Measurement Method for Difference of Flexo-coefficients (e<sub>11</sub>-e<sub>33</sub>) by Using Disclination Lines in HAN Cells with Concentric Rubbing Treatment

Proceedings of the International Display Workshops Volume 26 (IDW '19),Novel Measurement Method for Difference of Flexo-coefficients (e₁₁-e₃₃) by Using Disclination Lines in HAN Cells with Concentric Rubbing Treatment

Novel Measurement Method for Difference of Flexo-coefficients (e<sub>11</sub>-e<sub>33</sub>) by Using Disclination Lines in HAN Cells with Concentric Rubbing Treatment

Novel Measurement Method for Difference of Flexo-coefficients (e<sub>11</sub>-e<sub>33</sub>) by Using Disclination Lines in HAN Cells with Concentric Rubbing Treatment

P‐211: Late‐News Poster: A 5.5‐inch FHD IGZO in Cell Touch LCD with High SNR

We developed a 5.5” IGZO (Indium‐Gallium‐Zinc‐Oxide) LCD display with in cell touch of self‐capacitive type. The photoalignment instead of traditional rubbing treatment of the LCD substrate was adopted. Middle com structure with organical planarizaion layer possesses high display quality and excellent touch performance due to fewer couple between gate/data and pixel/Vcom.

Superior electro-optical performance in vertically aligned liquid crystal devices based on aluminum oxide films

ABSTRACTWe achieved vertically aligned (VA) liquid crystals (LCs) on aluminum oxide (Al2O3) films deposited via e-beam evaporation using a rubbing treatment. Uniform and vertical LC alignment was achieved and high thermal stability was obtained using these substrates. By analyzing measurements from optical retardations, we confirm that the LC orientation is adjustable using rubbing treatment. The superior electro-optical characteristics of the VA cells based on Al2O3 films are measured and compared with those based on polyimide layers, indicating that this approach will allow the fabrication of high-performance, advanced LC displays using a conventional rubbing process.

Mussel-inspired polyelectrolyte multilayer for reinforcing the interfacial mechanical stability of plasmonic microstructures

In this paper, mussel-inspired polyelectrolyte was prepared through grafting catechol-contained molecules onto the backbone of the polyelectrolyte, and then introduced between the plasmonic microstructures and substrates to reinforce the mechanical stability of the microstructures. The plasmonic microstructures with mussel-inspired adhesive multilayers show greatly improved mechanical stability against both rubbing and ultrasonic treatment without significant alteration of the original morphology and optical property. Additionally, label-free sensing could also be achieved with reasonable sensitivity. We believe that such stabilizing strategy based on mussel-inspired polyelectrolyte will show great potential towards practical applications of plasmonic microstructures, even in the presence of water or body fluid.

Electro-optical properties of liquid crystal displays based on the transparent zinc oxide films treated by using a rubbing method

Liquid crystal (LC) alignment on inorganic films has been found to be affected by surface modification via ion-beam irradiation. In this study, ZnO films treated by rubbing with a velvet cloth were shown to be capable of aligning LC molecules in the direction of the rubbing. Uniform and homogeneous LC alignment was achieved on the rubbed ZnO films. By analysing the optical axes before and after the rubbing treatment, we confirmed an increase in the anisotropy of the ZnO films; this optical anisotropy contributed to the uniform orientation of LC molecules. Further, the electro-optical characteristics of the twisted nematic cells based on ZnO films were superior to those based on conventional polyimide layers. Our results indicate that the rubbing approach could be applied in the fabrication of high-performance LC displays.

Aligned Growth of Methylene Blue Films on TiO2 Single Crystals

We found epitaxial growth of needle-like nanosized crystals of methylene blue (MB). The nanosized crystals grew spontaneously along the c-axis of the (110) surface of a TiO2 single crystal by using the dip-coating method from solution. This epitaxial growth of the nanosized crystals is induced by the bridging oxygen rows align along the crystal c-axis. We also found that the alignment direction could be controlled by rubbing the surface of the substrate prior to dye-loading. The memory of the alignment direction induced by the rubbing treatment was erased by thermal annealing at 620 K. These findings suggest that the nanostructure on the TiO2 surface plays an important role in the aligned growth of MB nanosized crystals.

Surface texturing effect on crack suppression of SiO2 film formed by F2 laser-induced photochemical surface modification of silicone on polycarbonate under heat resistance test

A crack-free SiO2 film was successfully fabricated on silicone-coated polycarbonate (PC) even under heat resistance tests at 100 and 120 °C for 3 h by an additional rubbing treatment with steel wool for use as an automobile window material. The SiO2 film was formed by 157 nm F2 laser-induced photochemical surface modification of silicone on PC. The modified SiO2 layer was also zoned with a mesh mask during the laser irradiation. The zoned SiO2 layer was effective for suppressing cracks during laser irradiation. However, even the zoned layer caused cracks under heat resistance tests. A mechanism of the cracking was analyzed on the basis of observations of sample surfaces by confocal laser microscopy. The rubbed samples showed high heat resistance. By atomic force microscopy, the surface of the modified SiO2 layer was clearly observed to be textured, which reduced the large difference in the thermal expansion coefficient between SiO2 and silicone on PC, thus maintaining optical transparency.