Effect of khat extract on color stability of digitally and manually fabricated provisional restorations: an in vitro comparative study.

BACKGROUND: The aim of this in vitro study was to evaluate the effect of khat extract on the color stability of five different provisional restorative materials (PRMs). METHODS: In this study, 50 specimens were fabricated from five different PRMs with different techniques. Twenty specimens were digitally fabricated of poly-methyl methacrylate (PMMA) CAD/CAM milling and 3D printing PRMs, while the other thirty specimens were manually fabricated of three different PRMs: PMMA self-cured (SC) acrylic resin, light-cured (LC) composite, and Bis-acrylic SC composite. Milling and 3D printing machines were used to fabricate the digital specimens, while the manual specimens were fabricated using a metallic mold. The material was placed in the mold, covered by a polyester stripe, and held between two glass slabs with a constant load for 30 s. After setting, the specimens were removed and checked. Ten disc-shaped specimens with 2 ± 0.3 mm thickness and 10 ± 0.3 mm diameter were prepared from each of the tested PRM. Then all the specimens were polished. Five specimens of each PRM were immersed in khat extract, while the other five were immersed in distilled water medium as a control group. The color measurements were recorded before and after 1 and 7 days of immersion using a spectrophotometer. The immersion media were renewed every 24 h and kept along with the specimens at 37 °C. The T test, paired T test, and ANOVA analysis of variance were used to analyze the results. The Bonferroni test was used for post-hoc multiple comparisons. RESULTS: The interaction between the tested PRMs, the media, and the duration of immersion time was statistically significant (p < 0.05). PMMA CAD/CAM milling PRM was the most stable in color, and this was statistically significant (p < 0.05). The LC composite PRM composite was the least stable in color and was statistically insignificant (p > 0.05) when compared to the 3D printing and Bis-acrylic SC composite PRMs, respectively. CONCLUSIONS: This study demonstrated that khat extract medium has a high staining ability on the tested PRMs. CAD/CAM milling PRM was the most stable in color and could therefore be used as a long-term provisional. The increase in immersion time was a significant factor in the color change of the tested PRMs. The color of the 3D-printed PRM was the most affected over time.

Surface, mechanical and chemical properties of modified denture resin using natural biopolymer.

Objective: This laboratory study determined the surface, mechanical and chemical properties of polymethyl methacrylate (PMMA) denture resin reinforced with micron-sized Gum Arabic (GA) powder in different weight ratios. Methods: This laboratory study was conducted at the Dental Health Department of the College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia from November 2022 to February 2023. Three experimental denture resins were prepared by incorporating GA powder in heat-polymerized PMMA powder using different wt.% (5, 10, and 20 wt.%). While pristine PMMA served as the control group. A total of ten bar-shaped specimens with dimensions of 65 mm × 10 mm × 3.5 mm were prepared for each study group. The surface properties (micro CT and SEM evaluation), mechanical properties (Nanohardness, elastic modulus and flexural strength) and chemical properties (FTIR) were conducted. The data were statistically analyzed using the one-way analysis of variance and Tukey's post hoc tests (p<0.05). Results: The surface and bulk properties of experimental GA-reinforced PMMA resin materials deteriorated while the mechanical properties were also negatively altered using GA-based PMMA denture resin. A linear correlation was observed between weak mechanical properties and increasing wt.% of GA in denture resin. Conclusions: The incorporation of GA powder in denture resin might not be a viable option. The surface and mechanical properties of experimental PMMA composites were adversely affected compared to the control group.

Effect of Gum Arabic powder on the mechanical properties of denture base acrylic.

Objective: This study aimed to improve the mechanical properties of denture base material using various concentrations of natural biopolymer, i.e., Gum Arabic (GA). Methods: This experimental study was conducted at the Dental Health Department of the College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia from May 2022 to July 2022. After obtaining exemption from the institutional review board, the powdered GA was added in ratios of weight 5, 10, and 20% to PMMA heat-cured acrylic powder to produce bar-shaped samples (65 × 10 × 30 mm3 in dimensions). While the control group was prepared as such. Micro hardness (n=10/group) and fracture toughness (n=10/group) were evaluated. One-way analysis of variance method was used to statistically analyze the results (p<0.05) using SPSS version 23. Results: Significant differences were observed for micro hardness (p<0.001) and fracture toughness (p=0.007) between the means of the different study groups. The control group exhibited the highest micro hardness (22.5±0.6 VHN) and fracture toughness (1.25±0.11 MPa.m1/2) value among the study groups. While 20 wt. % GA and 10 wt. % GA groups showed the lowest micro hardness and fracture toughness values, respectively. Conclusions: GA powder might not be an appropriate reinforcing material for denture base or the higher filler loading of GA in denture base acrylic might be detrimental to the mechanical properties.

Reconstruction of large cranial defects with poly-methyl-methacrylate (PMMA) using a rapid prototyping model and a new technique for intraoperative implant modeling.

BACKGROUND: Reconstruction of large cranial defects after craniectomy can be accomplished by free-hand poly-methyl-methacrylate (PMMA) or industrially manufactured implants. The free-hand technique often does not achieve satisfactory cosmetic results but is inexpensive. In an attempt to combine the accuracy of specifically manufactured implants with low cost of PMMA. METHODS: Forty-six consecutive patients with large skull defects after trauma or infection were retrospectively analyzed. The defects were reconstructed using computer-aided design/computer-aided manufacturing (CAD/CAM) techniques. The computer file was imported into a rapid prototyping (RP) machine to produce an acrylonitrile-butadiene-styrene model (ABS) of the patient's bony head. The gas-sterilized model was used as a template for the intraoperative modeling of the PMMA cranioplasty. Thus, not the PMMA implant was generated by CAD/CAM technique but the model of the patients head to easily form a well-fitting implant. Cosmetic outcome was rated on a six-tiered scale by the patients after a minimum follow-up of three months. RESULTS: The mean size of the defect was 74.36cm2. The implants fitted well in all patients. Seven patients had a postoperative complication and underwent reoperation. Mean follow-up period was 41 months (range 2-91 months). Results were excellent in 42, good in three and not satisfactory in one patient. Costs per implant were approximately 550 Euros. CONCLUSION: PMMA implants fabricated in-house by direct molding using a bio-model of the patients bony head are easily produced, fit properly and are inexpensive compared to cranial implants fabricated with other RP or milling techniques.

Machinability and Surface Properties of Cryogenic Poly(methyl methacrylate) Machined via Single-Point Diamond Turning.

Poly(methyl methacrylate) (PMMA), with a glass transition temperature (Tg) over 100 °C, shows good mechanical and optical properties and has broad applications after being machined with single-point diamond turning (SPDT) at room temperature. Because of the high Tg, current efforts mostly focus on optimizing machining parameters to improve workpiece precision without considering the modification of material properties. Cryogenic cooling has been proven to be an effective method in assisting ultra-precision machining for certain types of metals, alloys, and polymers, but has never been used for PMMA before. In this work, cryogenic cooling was attempted during the SPDT of PMMA workpieces to improve surface quality. The machinability and surface properties of cryogenically cooled PMMA were investigated based on the mechanical properties at corresponding temperatures. Nanoindentation tests show that, when temperature is changed from 25 °C to 0 °C, the hardness and Young's modulus are increased by 37% and 22%, respectively. At these two temperature points, optimal parameters including spindle speed, feed rate and cut depth were obtained using Taguchi methods to obtain workpieces with high surface quality. The surface quality was evaluated based on the total height of the profile (Pt) and the arithmetic mean deviation (Ra). The measurement results show that the values of Pt and Ra of the workpiece machined at 0 °C are 124 nm and 6 nm, respectively, while the corresponding values of that machined at 25 °C are 291 nm and 11 nm. The test data show that cryogenic machining is useful for improving the form accuracy and reducing the surface roughness of PMMA. Moreover, the relationship between temperature, material properties and machinability weas established with dynamic mechanical analysis (DMA) data and a theoretical model. This can explain the origin of the better surface quality of the cryogenic material. The basis of this is that temperature affects the viscoelasticity of the polymer and the corresponding mechanical properties due to relaxation. Then, the material property changes will affect surface profile formation during machining. The experimental results and theoretical analysis show that cryogenically cooled PMMA has good machinability and improved surface quality when using SPDT compared to that at ambient temperature.

Fabrication of a Microfluidic-Based Device Coated with Polyelectrolyte-Capped Titanium Dioxide to Couple High-Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometry for Mercury Speciation.

Mercury (Hg) is a toxic element which impacts on biological systems and ecosystems. Because the toxicity of Hg species is highly dependent on their concentration levels and chemical forms, the sensitive identification of the chemical forms of Hg-i.e., Hg speciation-is of major significance in providing meaningful information about the sources of Hg exposure. In this study, a microfluidic-based device made of high-clarity poly(methyl methacrylate) (PMMA) was fabricated. Then, titanium dioxide nanoparticles (nano-TiO2s) were attached to the treated channel's interior with the aid of poly(diallyldimethylammonium chloride) (PDADMAC). After coupling the nano-TiO2-coated microfluidic-based photocatalyst-assisted reduction device (the nano-TiO2-coated microfluidic-based PCARD) with high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), a selective and sensitive, hyphenated system for Hg speciation was established. Validation procedures demonstrated that the method could be satisfactorily applied to the determination of mercury ions (Hg2+) and methylmercury ions (CH3Hg+) in both human urine and water samples. Remarkably, the zeta potential measured clearly indicated that the PDADMAC-capped nano-TiO2s with a predominance of positive charges indeed provided a steady force for firm attachment to the negatively charged device channel. The cause of the durability of the nano-TiO2-coated microfluidic-based PCARD was clarified thus.

The Effects of Ozone Sterilization on the Chemical and Mechanical Properties of 3D-Printed Biocompatible PMMA.

Since ozone is highly corrosive, it can substantially affect the mechanical and chemical properties of the materials; consequently, it could affect the applicability of those materials in medical applications. The effect of ozone sterilization on the chemical and mechanical properties of additively manufactured specimens of biocompatible poly(methyl-methacrylate) was observed. FDM 3D-printed specimens of biocompatible PMMA in groups of five were exposed to high concentrations of ozone generated by corona discharge for different durations and at different ozone concentrations inside an enclosed chamber with embedded and calibrated ozone, temperature, and humidity sensors. A novel approach using laser-induced fluorescence (LIF) and spark-discharge optical emission spectrometry (SD-OES) was used to determine an eventual change in the chemical composition of specimens. Mechanical properties were determined by testing the tensile strength and Young's modulus. A calibrated digital microscope was used to observe the eventual degradation of material on the surface of the specimens. SD-OES and LIF analysis results do not show any detectable sterilization-caused chemical degradation, and no substantial difference in mechanical properties was detected. There was no detectable surface degradation observed under the digital microscope. The results obtained suggest that ozone sterilization appears to be a suitable technique for sterilizing PMMA medical devices.

Direct deep UV lithography to micropattern PMMA for stem cell culture.

Microengineering is increasingly being used for controlling the microenvironment of stem cells. Here, a novel method for fabricating structures with subcellular dimensions in commonly available thermoplastic poly(methyl methacrylate) (PMMA) is shown. Microstructures are produced in PMMA substrates using Deep Ultraviolet lithography, and the effect of different developers is described. Microgrooves fabricated in PMMA are used for the neuronal differentiation of mouse embryonic stem cells (mESCs) directly on the polymer. The fabrication of 3D, curvilinear patterned surfaces is also highlighted. A 3D multilayered microfluidic chip is fabricated using this method, which includes a porous polycarbonate (PC) membrane as cell culture substrate. Besides directly manufacturing PMMA-based microfluidic devices, an application of the novel approach is shown where a reusable PMMA master is created for replicating microstructures with polydimethylsiloxane (PDMS). As an application example, microchannels fabricated in PDMS are used to selectively expose mESCs to soluble factors in a localized manner. The described microfabrication process offers a remarkably simple method to fabricate for example multifunctional topographical or microfluidic culture substrates outside cleanrooms, thereby using inexpensive and widely accessible equipment. The versatility of the underlying process could find various applications also in optical systems and surface modification of biomedical implants.

Metabolic engineering of low-pH-tolerant non-model yeast, Issatchenkia orientalis, for production of citramalate.

Methyl methacrylate (MMA) is an important petrochemical with many applications. However, its manufacture has a large environmental footprint. Combined biological and chemical synthesis (semisynthesis) may be a promising alternative to reduce both cost and environmental impact, but strains that can produce the MMA precursor (citramalate) at low pH are required. A non-conventional yeast, Issatchenkia orientalis, may prove ideal, as it can survive extremely low pH. Here, we demonstrate the engineering of I. orientalis for citramalate production. Using sequence similarity network analysis and subsequent DNA synthesis, we selected a more active citramalate synthase gene (cimA) variant for expression in I. orientalis. We then adapted a piggyBac transposon system for I. orientalis that allowed us to simultaneously explore the effects of different cimA gene copy numbers and integration locations. A batch fermentation showed the genome-integrated-cimA strains produced 2.0 g/L citramalate in 48 h and a yield of up to 7% mol citramalate/mol consumed glucose. These results demonstrate the potential of I. orientalis as a chassis for citramalate production.

Assessing the Impact and Suitability of Dense Carbon Dioxide as a Green Solvent for the Treatment of PMMA of Historical Value.

Surface cleaning of plastic materials of historical value can be challenging due to the high risk of inducing detrimental effects and visual alterations. As a result, recent studies have focused on researching new approaches that might reduce the associated hazards and, at the same time, minimize the environmental impact by employing biodegradable and green materials. In this context, the present work investigates the effects and potential suitability of dense carbon dioxide (CO2) as an alternative and green solvent for cleaning plastic materials of historical value. The results of extensive trials with CO2 in different phases (supercritical, liquid, and vapor) and under various conditions (pressure, temperature, exposure, and depressurization time) are reported for new, transparent, thick poly(methyl methacrylate) (PMMA) samples. The impact of CO2 on the weight, the appearance of the samples (dimensions, color, gloss, and surface texture), and modifications to their physicochemical and mechanical properties were monitored via a multi-analytical approach that included optical microscopy, Raman and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies, and micro-indentation (Vickers hardness). Results showed that CO2 induced undesirable and irreversible changes in PMMA samples (i.e., formation of fractures and stress-induced cracking, drastic decrease in the surface hardness of the samples), independent of the conditions used (i.e., temperature, pressure, CO2 phase, and exposure time).

Energy Consumption vs. Tensile Strength of Poly[methyl methacrylate] in Material Extrusion 3D Printing: The Impact of Six Control Settings.

The energy efficiency of material extrusion additive manufacturing has a significant impact on the economics and environmental footprint of the process. Control parameters that ensure 3D-printed functional products of premium quality and mechanical strength are an established market-driven requirement. To accomplish multiple objectives is challenging, especially for multi-purpose industrial polymers, such as the Poly[methyl methacrylate]. The current paper explores the contribution of six generic control factors (infill density, raster deposition angle, nozzle temperature, print speed, layer thickness, and bed temperature) to the energy performance of Poly[methyl methacrylate] over its mechanical performance. A five-level L25 Taguchi orthogonal array was composed, with five replicas, involving 135 experiments. The 3D printing time and the electrical consumption were documented with the stopwatch approach. The tensile strength, modulus, and toughness were experimentally obtained. The raster deposition angle and the printing speed were the first and second most influential control parameters on tensile strength. Layer thickness and printing speed were the corresponding ones for the energy consumption. Quadratic regression model equations for each response metric over the six control parameters were compiled and validated. Thus, the best compromise between energy efficiency and mechanical strength is achievable, and a tool creates significant value for engineering applications.

Antibiotic release from PMMA spacers and PMMA beads measured with ELISA: Assessment of in vitro samples and drain fluid samples of patients.

For prosthetic joint infections, antibiotic loaded poly methyl methacrylate (PMMA) spacer or beads can be used to release high concentrations of antibiotics locally at the infection site, while minimizing systemic toxicity. The aim of this study is to determine in vitro and in vivo pharmacokinetic release profile of antibiotics from PMMA spacers and PMMA beads. For the in vitro experiment, the PMMA spacers or beads were submerged in phosphate-buffered saline and gentamicin concentrations were determined from collected specimen at several times points, measured with enzyme-linked immunosorbent assays (ELISA). To assess the in vivo antibiotic release profile of different spacers, wound drainage fluid samples were collected after implantation of a spacer over a period of maximum 14 days. After 48 h, the burst gentamicin concentration elution was 9862 ± 1782 ng/ml (mean ± SD) from spacers versus 38,394 ± 7071 ng/ml (mean ± SD) for beads. Over 35 days, spacers had eluted a cumulative mean concentration of 13,812 ± 3548 versus 55,048 ± 12,006 ng/ml for beads (p < 0.001). Clinical samples of patients with a Vancogenx® spacer showed higher gentamicin release than Refobacin™ spacers (p < 0.001). This is the first study that measured the release data of local antibiotics with ELISA. Compare to spacers, the exact release values of gentamicin from PMMA beads are more than 10 times higher and reached a maximum much later than spacers. This makes the use of PMMA beads more preferable to use for treatment of the infection itself.

Porous titanium microsphere kyphoplasty for augmentation treatment of osteoporotic vertebral fractures: Technical report and case series.

Background: Vertebral augmentation procedures (VAPs) are used in cases of persistent and unresponsive pain in patients with vertebral compression fractures (VCFs). Although VAPs are considered a safe procedure providing quick pain relief and improved physical function, some postoperative complications can occur, for example, bone cement leakage. The material used in this procedure is almost exclusively polymethyl methacrylate (PMMA), which appears to lack biological activity and osteointegration capabilities. In this study, we introduce a new filling system consisting of cannulas preloaded with titanium microspheres, which stabilizes and consolidates the structure of the vertebral body in treating VCFs after the performance of the kyphoplasty procedure. Methods: We report a retrospective case series of six patients affected by osteoporotic vertebral fractures with worsening back pain, neurologic impairment, and failed conservative treatment who underwent the VAP at our institute, for which the SPHEROPLAST [MT ORTHO s.r.l., Aci Sant'Antonio (CT), Italy] system was used. Results: The patients had failed an average conservative trial of 3.9 weeks before they presented to us with neurodeficit. There were two men and four women with a mean age of 74.5 years. The average hospital stay was 2 days. There were no reported perioperative complications related to cement injection, such as intraoperative hypoxia, hypotension, pulmonary embolization, myocardial infarction, neurovascular or viscera injury, or death. The VAS score significantly decreased from a mean preoperative of 7.5 (range 6-19) to 3.8 (range 3-5) immediately after surgery and 1.8 (range 1-3). Conclusion: We report the first clinical results in a series of six patients treated for VCF using the microsphere system after analyzing the clinical results produced by, and the complications that arose from, this new device. In patients with VCF, the VAP using titanium microspheres appears to be a feasible and safe procedure with a low risk of material leakage.

CO2-Laser-Micromachined, Polymer Microchannels with a Degassed PDMS slab for the Automatic Production of Monodispersed Water-in-Oil Droplets.

In our recent study, we fabricated a pump/tube-connection-free microchip comprising top and bottom polydimethylsiloxane (PDMS) slabs to produce monodispersed water-in-oil droplets in a fully automated, fluid-manipulation fashion. All microstructures required for droplet production were directly patterned on the surfaces of the two PDMS slabs through CO2-laser micromachining, facilitating the fast fabrication of the droplet-production microchips. In the current extension study, we replaced the bottom PDMS slab, which served as a microfluidic layer in the microchip, with a poly(methyl methacrylate) (PMMA) slab. This modification was based on our idea that the bottom PDMS slab does not contribute to the automatic fluid manipulation and that replacing the bottom PDMS slab with a more affordable and accessible, ready-to-use polymer slab, such as a PMMA, would further facilitate the rapid and low-cost fabrication of the connection-free microchips. Using a new PMMA/PDMS microchip, we produced water-in-oil droplets with high degree of size-uniformity (a coefficient of variation for droplet diameters of <5%) without a decrease in the droplet production rate (~270 droplets/s) as compared with that achieved via the previous PDMS/PDMS microchip (~220 droplets/s).

Recent Achievements on Grating Fabrications in Polymer Optical Fibers with Photosensitive Dopants: A Review.

This review discusses recent achievements on grating fabrications in polymer optical fibers doped with photosensitive materials. First, different photosensitive dopants in polymer optical fibers (POFs) are summarized, and their refractive index change mechanisms are discussed. Then, several different doping methods to fabricate the photosensitive POFs are presented. Following that, the principles of gratings, including standard fiber Bragg gratings (FBGs), tilted fiber Bragg gratings (TFBGs), chirped fiber Bragg gratings (CFBGs), phase-shifted fiber Bragg gratings (PSFBGs), and long period fiber gratings (LPFGs), are reported. Finally, fabrications of different gratings based on photosensitive POFs in the last 20 years are reported. We present our article clearly and logically, so that it will be helpful for researchers to explore a broad perspective on this proposed topic. Overall, the content provides a comprehensive overview of photosensitive POF fabrications and grating inscriptions in photosensitive POFs, including previous breakthroughs and recent advancements.

Miscibility and thermal behavior of poly(methyl methacrylate) and polystyrene blend using benzene as a common solvent.

Polymer blending is one of the advanced technologies to attain polymeric material with tailored properties. In this work, the miscibility of Poly(methyl methacrylate) (PMMA) and Polystyrene (PS) blend in benzene was investigated by employing various techniques such as FTIR spectroscopy, viscosity measurement technique, light scattering techniques, DSC and TGA techniques over an extended range of concentrations, compositions, and temperatures. The results revealed that there exist hydrogen bonding and hydrodynamic interactions which led these polymers to get miscible to a large extent. The compatibility increased with the increasing PS contents or increase in temperature of the system. In addition, the thermal stability of blends was found to be improved with the increase in the compatibility of the polymer.

Multi-Objective Optimization of Nd: YAG Laser Drilling of Optical-Grade Acrylic Plate Using Taguchi-Based Grey Relational Analysis.

This study proposed an effective method for optimizing laser drilling processing (LDP) by using grey relational analysis (GRA) for multiple performance requirements. First, we developed a system using a Quantel Brilliant Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser with a pulse width of 5-6 ns and F-theta lenses to deliver a focused laser beam with a diameter of 0.2 mm. The developed system was first employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate on a safe window with a high optical density and a grade of OD 7+ @ 950~1085 nm. To avoid errors in the experimental data due to unstable power, a laser power (energy) meter was used to measure the energy stability of the Quantel Brilliant Pulse Laser. Given the stability of 5.6%, this is an effective method for LDP. Four control factors were investigated, including laser pulse energy, repetition rate, focusing position offset, and drilling time. Then, nine experiments were performed using the Taguchi method with orthogonal arrays in L9 (34). The experimental results with multiple quality characteristics were measured and used to optimize the control factors by using GRA with equal weighting of the four qualities (roundness, Hillock ratio, taper, and HAZ). The results show that A1B3C1D1 is the optimal combination of the control factors, and the maximal variation of 0.406 is obtained from the control factor B (focusing position offset) which has the greatest contribution to the drilling time. We then performed confirmation experiment and obtained a better result from the combination of the control factors, A1B3C1D1. GRA helps us determine the best laser drilling parameters to meet the desired multiple drilling qualities.

FECO fringes for investigating the effect of grafting process on the dispersion properties of polyamaide-6 fibers.

Polyamide-6 fiber was modified by grafting it with poly(methyl methacrylate) PMMA polymer. The grafting process is widely used in industry to introduce new properties and overcome some obstacles, for instance, in storing energy applications. Multiple-beam interference techniques are very precise techniques to characterize the different properties of polymeric fibers. Fringes of equal chromatic order FECO technique was used to study the effect of grafting process on the dispersion properties of polyamides fibers. A mechanical drawing device was attached to the FECO system to evaluate the mechanical deformation impact on the samples and on their dispersion properties. The dispersion properties were evaluated by measuring their refractive indices, Cauchy's constants, average excitation energy, dispersion energy, lattice energy, interband oscillator wavelength, static dielectric constant, and Abbe's dispersion number. The results show that grafting polyamide-6 with PMMA produced a new material with a different structure and different dispersion properties. Microinterferograms, graphs and tables were given for illustrations.

Poly(acrylic acid) as an adhesion promoter for UV-assisted thermoplastic bonding: Application for the in vitro construction of human blood vessels.

In this study, we introduced a novel adhesion bonding method for fabricating thermoplastic microdevices using poly(acrylic acid) (PAA) as a UV-assisted adhesion promoter. The bonding mechanism was based on the covalent cross-links between poly(methyl methacrylate) (PMMA) and PAA via the free radicals in their carbon backbone generated under UV irradiation. The water contact angle and Fourier-transformed infrared (FTIR) analysis were performed to analyze the surface characteristics of the PAA-coated PMMA. PMMAs were bonded under UV treatment for 60 s with the highest bond strength of around 1.18 MPa. The PMMA microdevice was leak-proof for over 200 h. Besides, clog-free PMMA microdevices with various-sizes microchannels were performed to demonstrate such a high applicable bonding method for microdevice fabrication. Moreover, PMMAs were bonded with other thermoplastics with a bond strength of around 0.5 MPa. Notably, collagen was easily coated inside the PMMA microchannels via electrostatic interaction between PAA and collagen which is beneficial for on-device cell culture. As a result, a layered co-culture model of smooth muscle cells (SMCs) and human umbilical vein endothelial cells (HUVECs) was realized inside simple straight microchannels mimicking human blood vessel wall. Therefore, the introduced bonding method could pave the way for fabricating microdevice for cell-related applications.

Is Poly(methyl methacrylate) (PMMA) a Suitable Substrate for ALD?: A Review.

Poly (methyl methacrylate) (PMMA) is a thermoplastic synthetic polymer, which displays superior characteristics such as transparency, good tensile strength, and processability. Its performance can be improved by surface engineering via the use of functionalized thin film coatings, resulting in its versatility across a host of applications including, energy harvesting, dielectric layers and water purification. Modification of the PMMA surface can be achieved by atomic layer deposition (ALD), a vapor-phase, chemical deposition technique, which permits atomic-level control. However, PMMA presents a challenge for ALD due to its lack of active surface sites, necessary for gas precursor reaction, nucleation, and subsequent growth. The purpose of this review is to discuss the research related to the employment of PMMA as either a substrate, support, or masking layer over a range of ALD thin film growth techniques, namely, thermal, plasma-enhanced, and area-selective atomic layer deposition. It also highlights applications in the selected fields of flexible electronics, biomaterials, sensing, and photocatalysis, and underscores relevant characterization techniques. Further, it concludes with a prospective view of the role of ALD in PMMA processing.