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In this paper, we demonstrated an optical fiber biosensor based on heterodyne demodulation to detect five pathogenic bacteria species forming biofilms, such as Escherichia Coli, Vibrio Vulnificus, Pseudomonas Aeruginosa, Staphylococcus Aureus, and Streptococcus Iniae, with their fluorescence characteristics. The proposed sensor detects the fluorescence of the five bacteria species with the intrinsic fluorescence characteristics of amino acid tryptophan, whose excitation and emission wavelengths are 280 and 350 nm, respectively. The fabricated sensor consists of an UV light source for excitation of bacteria, a high sensitivity detector for detection of fluorescence signals emitted from the excited bacteria, and a lock-in amplifier for amplification of the detected fluorescence signals. The lock-in amplifier can remove various noise signals coupled with the desired fluorescence signals and amplify the magnitude of the desired signal through the heterodyne demodulation technique. This signal processing technique enables the detection of the weak picowatt (pW) fluorescence signals. Consequently, it is concluded that our sensor can successfully detect the intensity of the fluorescence signal emitted from five pathogenic bacteria species whose concentration lies within 10² to 107 CFU/ml.

The present study evaluated the effect of fucoidan/alginate-polyethylene glycol-gellan gum (Fu/AL-PEG@GGH) hydrogel using low-level laser therapy (LLLT) on facilitating wound healing for wound care management. The hydrogel was fabricated and characterized to evaluate the wound healing potential. Cytotoxicity and apoptotic effects were evaluated with L929 and NIH3T3 cells. Uniform spherical sheets were observed with high thermal stability caused by porous matrixes with the increased cell viability and fast cell migration. Scar tissue was reduced by larger wound contraction with faster healing effects from the hydrogel + LLLT-treated group at day 14. The polysaccharides may promote wound healing due to the strong bonds by the physical cross-linking in hydrogel preparation. The results from hydrogel + LLLT-treated group confirmed an effective wound healing potential from the presence of high fibroblast and collagen deposition. Therefore, the combined practice of the hydrogel with LLLT may enhance a wound healing process for effective wound care applications.

Among various methods to produce graphene sheets, electrochemical exfoliation has been regarded as an effective method for the mass production of high-quality graphene sheets because of its simplicity and environmental friendliness. However, conventional electrochemical exfoliation has a disadvantage of accumulating intercalating ions at graphite interlayers owing to the use of a constant voltage. In this study, we developed a DC switching technique to achieve more efficient intercalation of ions than that in the conventional method. In the DC switching method, positive and negative voltages are successively applied to release the accumulated intercalating ions. By testing various conditions, we found the optimum switching time to produce high-quality graphene sheets with the highest yield rate and the highest electrical conductivity. As a result, the graphene sheets using this DC switching technique showed 85% higher yield rate, 193% higher electrical conductivity, 160% larger area, and 25% thinner thickness than those obtained when using a constant DC method. We believe that this DC switching technique can be used for large-scale production of high-quality graphene sheets.

Barrett's esophagus (BE) is associated with an intestinal metaplasia that replaces normal squamous epithelium by columnar epithelium. The aim of the current study was to evaluate the feasible endoscopic treatment on esophageal tissue with circumferential laser irradiation. A 532-nm laser was used to deliver 10 W in a continuous manner through a balloon catheter-integrated diffuser. Ex vivo leporine esophagus was tested to identify thermal responses at various irradiation times. In vivo testing in a porcine model was performed to evaluate the feasibility of endoscopic application with the integrated device for BE treatment. Goniometric measurements confirmed that the proposed device yielded uniform radial irradiation (i.e., 0.9 ± 0.1 in arbitrary unit). Emission profiles were well correlated with temperature distribution along the device. Ex vivo leporine testing demonstrated that the temperature rise increased with irradiation time. The maximum temperature increase was around 38 °C after 60-s irradiation (transient increase rate = 0.62 °C/s), and the corresponding thermal coagulation reached esophageal submucosa (1.5 ± 0.2 mm). In vivo porcine testing evidently presented circumferential thermal denaturation around the lumen along with mild inflammatory reaction and the degenerated squamous epithelium. The overall thickness of the irreversible thermal coagulation was 3.1 ± 0.2 mm. The proposed photothermal therapy can be a feasible endoscopic method to treat BE with the aid of circumferential irradiation and mechanical expansion. Further chronic in vivo testing will be pursued to understand chronic tissue response in terms of wound healing and complication.

A nanofiber membrane with a high surface-to-volume ratio has advantages in applications such as those used for particulate matter filtration and gas detection. To maximize the potentials of the membrane structure, recent research has been attempted to control nanofiber geometries. In this paper, surface modification of a nanofiber membrane with a metal/ceramic nanostructure is performed to improve multi-functional filter performance, enhancing fine particle filtration and toxic gas absorption. Here, a smart filter is fabricated by electrospinning polyvinylidene difluoride (PVDF) nanofiber onto a nylon mesh and hydrothermal synthesis of ZnO nanoparticles onto a nanowire array on a PVDF nanofiber surface. On the ZnO nanowires–PVDF nanofiber layer filter, the pressure difference (ΔP = 4.13 kPa) is higher than the pure PVDF nanofiber layer. However, the filtration efficiency is 94.3% for a 0.3 μm particle size, which is higher than that of other sizes. Additionally, a ZnO nanowire array with high density on a PVDF nanofiber layer affects sensitivity (S = 39.37), with high resolution. The photocurrent characteristics of a smart filter have the potential for a photo-assisted redox reaction to detect toxic polar molecules in continuous airflow in real-time in indoor environments.

The current study aims to evaluate the dependence of laser-induced optical breakdown (LIOB) on skin types by using 1064 nm picosecond laser with micro-lens arrays (MLA) and diffractive optical elements (DOE). Both black and white skin tissues were examined to comparatively assess the LIOB effects in the skin in terms of laser-induced vacuolization. The black skin irradiated at 3.0 J/cm2 demonstrated that MLA yielded a deeper distribution (180-400 μm) of laser-induced vacuoles with a size of 67 μm, compared to DOE (180-280 μm; 40 μm in size). However, the white skin presented that MLA created larger vacuoles (134 μm in size) in a smaller number at deeper distributions (125-700 μm) than MLA with the black skin. DOE generated no laser-induced vacuolization in the white skin. The white skin tissue with inherent higher scattering could be responsible for deeper vacuolization after the picosecond laser treatment. Further investigations are expected to determine the optimal treatment conditions for various skin types.

Laser ablation can be used to treat atrial fibrillation by thermally isolating pulmonary veins. In this study, we evaluated the feasibility of high-resolution (1 mm) ultrasound thermal imaging to monitor spatial temperature distribution during laser ablation on ex vivo cardiac tissue.Laser ablation (808 nm) was performed on five porcine cardiac tissue samples. A thermocouple was used to measure the interstitial tissue temperature during the laser ablation process. Tissue-strain-based ultrasound thermal imaging was conducted to monitor the spatial distribution of the temperature in the cardiac tissue. The tissue temperature was estimated from the time shifts of ultrasound signals owing to the changes in the speed of sound and was compared with the measured temperature. The temperature estimation coefficient k of porcine cardiac tissue was calculated from the estimated thermal strain and the measured temperature. The degree of tissue coagulation (temperatures 50°C) was derived from the estimated temperature and was compared with that of the tested cardiac tissue.The estimated tissue temperature using strain-based ultrasound thermal imaging at a depth of 1 mm agreed with thermocouple measurements. During the 30-second period of the laser ablation process, the estimated tissue temperature increased from 25 to 70°C at a depth of 0.1 mm, while the estimated temperature at a depth of 1 mm increased up to 46°C. Owing to the uncertainty of the coefficient k, the k value of the porcine cardiac tissue varied from 160 to 220°C with temperature changes of up to 20°C. The estimated coagulation region in the ultrasound thermal imaging was 20% wider (+0.6 mm) but 9% shallower (-0.1 mm) than the measured region of the ablated porcine cardiac tissue.The current study demonstrated the feasibility of temperature monitoring with the use of ultrasound thermal imaging during the laser ablation on ex vivo porcine cardiac tissue. The high-resolution ultrasound thermal imaging could map the spatial distribution of the tissue temperature. The proposed method can be used to monitor the temperature and thermal coagulation to achieve effective laser ablation for atrial fibrillation. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Prolonged endotracheal intubation is the most common cause of tracheal stenosis, which may lead to serious airway obstruction. Development of an endotracheal tube coated with biomaterials that exhibit anti-inflammatory or anti-fibrogenic effects may prevent tracheal stenosis. This study demonstrates that an endotracheal tube coated with phlorotannin, which is present in extracts of the brown alga Ecklonia cava, can prevent tracheal stenosis in a rabbit model. An in vitro study shows that phlorotannin inhibits proliferation of human tracheal fibroblasts treated with transforming growth factor β1. Phlorotannin-coated endotracheal tubes show steady release of phlorotannin for up to 7 days, and removal of the tube 1 week after insertion reveals a reduction in both fibrogenesis and thickening of tracheal submucosa. Western blot analysis of tracheal tissues after removal of the phlorotannin-coated tube shows decreased protein expression levels of phenotypic markers of fibrosis such as collagen type I and α-smooth muscle actin. The ability of phlorotannin-coated endotracheal tube to prevent tracheal stenosis caused by endotracheal intubation indicates that phlorotannin may be considered as a candidate biomaterial for coating the cuff of endotracheal tubes to prevent tracheal stenosis.

In this study, we introduce a noble method for the fabrication of highly crystalline hybrid TiO2-SiO2 thin films using laser irradiation under ambient conditions. Upon light absorption at the interface between TiO2 sol-gel film and Si wafer during the laser irradiation process, the TiO2 gel film coated on the Si wafer is transformed into anatase TiO2 film, and the surface of underlying Si wafer is oxidized to a 20.63 μm thick SiO2 film composed of nano-spheres with average diameter of 24.12 nm. The photocatalytic characteristics of the TiO2-SiO2 hybrid film on methylene blue and its discriminated morphologies are compared with those of a TiO2 film fabricated by conventional thermal annealing. The TiO2-SiO2 hybrid film shows enhanced super-hydrophilicity and superior photocatalytic characteristics, while thermally annealed 0.16 μm thick TiO2 films exhibit hydrophobic and low photocatalytic properties. The laser assisting process is promising for the fabrication of highly crystalline TiO2-SiO2 hybrid film with super-hydrophilic and photocatalytic characteristics.

Poly(lactide-co-glycolide) (PLGA) is one of the most widely used bioplastics in bioengineering and has been actively applied to fused deposition modeling (FDM)-based 3D printing. However, the brittleness of PLGA remains a major obstacle to its application in FDM systems, because these systems can only process flexible materials. Here, we developed a new technique to enhance the flexibility of PLGA. A polymer drawing process involving bidirectional extension was applied to induce molecular alignment, which affects the flexibility of the material. Filamentous forms of PLGA with various draw ratios were prepared and their material properties were investigated in detail. The results showed that PLGA flexibility was markedly increased at the draw ratio of 3, which was identified as the brittle-to-ductile transition point. The elongation at break of the drawn PLGA at this draw ratio was approximately 14 times greater than that of the raw material. Printability tests showed that various complex 3D structures could be fabricated with the drawn PLGA using a FDM system. In addition, the drawn PLGA showed no cytotoxicity in culturing. The technique developed here shows potential for the preparation of long and flexible PLGA filaments for use in FDM technology with biological applicability.

Guided surgery often encounters signal saturation and noise, due to strong illumination from the surgical light. The current study developed a customized optical probe filtering incident wavelengths of ≥800 nm to selectively detect near-infrared (NIR) fluorescence signals under strong illumination. The feasibility of the fabricated filter for fluorescence imaging was evaluated with tubes containing indocyanine green (ICG) and lymph nodes in vivo mouse models. The fluorescent images were acquired under three different conditions for comparison: dark room (DR), conventional surgical light (CSL), and filter-assisted surgical light (FSL). ICG at the concentration of 0.7 μg/ml yielded the highest signal intensity Both DR and FSL yielded higher image contrasts (87.3% and 82.6%) compared to CSL (67.0%). The in vivo results confirmed that the proposed optical probe enhanced the image contrast of the lymph nodes in mice by three-fold (i.e., 16.7±4.4% for CSL vs. 55.6±5.0% for FSL; p < 0.05). However, the condition involving DR (68.5±2.4%) continued to generate a slightly higher image contrast compared to that involving FSL. Thus, we can effectively use the NIR fluorescence imaging system simultaneously in the improved surgical light source by the proposed method.

As water scarcity has become a major global problem, fog-harvesting technologies are considered an effective sustainable solution for water resources. Here, we report a novel approach to the fog-harvesting technology using zinc oxide-silver hierarchical nanostructures to mimic the Stenocara beetle’s back. Vertically aligned zinc oxide nanowires are first fabricated by a cost-effective and scalable hydrothermal method to produce a superhydrophilic surface. Silver nanoparticles are then selectively synthesized by an additional photo-induced synthetic process on the zinc oxide nanowire surfaces to form a hydrophobic surface using the hierarchical nanostructures. The fog-harvesting performance was investigated using an artificial fog flow and by measuring the amount of harvested water for efficient fog harvesting. On the superhydrophilic surface, although the water droplets immediately were captured, they formed a puddle at the bottom of the surface due to the high adhesion between water and the surface. In contrast, on the hydrophobic surface, the capturing rate was very low even though the water droplets easily rolled off the surface. Compared to the non-patterned surface, the captured water film on the patterned hydrophilic region grew rapidly into a spherical shape and separated from the surface due to the surrounding hydrophobic regions. As a result, the patterned surface with 0.5 mm pattern size afforded a higher fog collection rate of 1233 mg/h than those of the superhydrophilic and hydrophobic surfaces of 1105 mg/h and 879 mg/h respectively.

The goal of the current research is to identify dependence of photothermal responses on wavelengths for diffuser-assisted treatment of liver tumor. For interstitial photothermal treatment, four commercially available wavelengths were tested: 532, 808, 980, and 1470 nm. A thermal camera was employed to record spatio-temporal development of temperature in porcine liver tissue. Spatial distribution of temperature and coagulation was quantitatively evaluated at various irradiation times. Both 808 and 980 nm presented a comparable maximum temperature after delivery of 200 J. On the other hand, both 532 and 1470 nm induced the higher maximum temperatures of over 90 °C along with a wider thermal distribution. The degree of the coagulation for both 532 and 1470 nm was quite consistent along the diffusing tip as various distances showed the comparable coagulation thickness. Both 808 and 980 nm presented the varying degree of the coagulation (1 ~ 2 mm in thickness). The largest volume along the thickest radial coagulation was observed after 1470 nm laser irradiation (606.9 ± 21.0 mm3) whereas the smallest volume was created by 980 nm (77.1 ± 13.3 mm3). The current results demonstrated that due to strong light absorption, both 532 and 1470 nm could be the feasible wavelengths for the treatment of liver tumor.

Here, we investigate a circle electrode in the electrospinning process for the fabrication of substrate-free, freestanding nanofiber films. Circle electrode-based electrospinning is controlled by varying the applied voltage and the metal needle tip-to-collector distance. The equipment used for the voltage source and syringe pump is the same as those in traditional electrospinning. A hollow cylinder is used as the circle electrode to ensure stable electrostatic conditions on the top surface of the cylinder collector. Many studies of electrospinning have presented parameters for optimal film fabrication that are inadequate for film fabrication on wire electrode-based electrospinning. To overcome obstacles inherent to substrate-free film fabrication, the voltage and tip-to-collector distance are controlled in the circle electrode-based electrospinning process. Numerical simulation is used to determine the electric field in the electrospinning process for quantitative analysis. Under voltages of 6–18 kV and tip-to-collector distances of 30–100 mm, a freestanding film is successfully fabricated on a circle electrode with 20-mm inner diameter. The freestanding electrospun film can be transferred as a coating to a non-planar surface without using additional processes. Thus, the electrospinning process using the circle electrode collector was successfully optimized for freestanding film fabrication. Substrate-free electrospun films can be applied to multifunctional filters for dust filtration with humidity blocking. Regarding future applications, the circle electrode-based electrospinning process verified the potential for integrating freestanding electrospun films into organs-on-chip, biochemical sensors, and microfluidic analysis systems.

Holmium:YAG laser has been the lithotrite of choice for around 30 years in kidney stone surgery. Lasers have evolved over the years to offer higher power, increased pulse frequencies and longer pulse durations. The drivers for change have been to improve stone ablation and to minimise retropulsion. We report on a new prototype Holmium laser that fires multiple “micro-pulses” in “pulse packets” and discuss the stone phantom ablation rate results utilizing a bench model. The prototype laser demonstrated impressive stone ablation rates in our bench testing across a range of power settings. We will discuss the details of these results supporting that pulse-modulation with packets of micro-pulses are a promising technological development. (Disclaimers: Bench Test results may not necessarily be indicative of clinical performance. The testing was performed by or on behalf of BSC.

Stone retropulsion during laser lithotripsy results from various physical phenomena such as recoil momentum, bubble dynamics, and subsequent jet formation. Considerable stone retropulsion has been observed whereby the optical energy is converted into both mechanical and thermal energy as a distinctive bubble generation and collapse. It is hypothesized that by reducing the peak power and lengthening the pulse duration, we can reduce this conversion of optical energy into mechanical energy. This should maximize the thermal effects on the stone leading to enhanced ablation efficiency as well as less stone “chasing”. We are reporting on a new prototype Holmium laser with low pulse power and long temporal pulse durations in an attempt to minimize stone retropulsion.

Demineralized dentin matrix (DDM)-based materials have been actively developed and are well-known for their excellent performance in dental tissue regeneration. However, DDM-based bio-ink suitable for fabrication of engineered dental tissues that are patient-specific in terms of shape and size, has not yet been developed. In this study, we developed a DDM particle-based bio-ink (DDMp bio-ink) with enhanced three-dimensional (3D) printability. The bio-ink was prepared by mixing DDM particles and a fibrinogen–gelatin mixture homogeneously. The effects of DDMp concentration on the 3D printability of the bio-ink and dental cell compatibility were investigated. As the DDMp concentration increased, the viscosity and shear thinning behavior of the bio-ink improved gradually, which led to the improvement of the ink’s 3D printability. The higher the DDMp content, the better were the printing resolution and stacking ability of the 3D printing. The printable minimum line width of 10% w/v DDMp bio-ink was approximately 252 μm, whereas the fibrinogen–gelatin mixture was approximately 363 μm. The ink’s cytocompatibility test with dental pulp stem cells (DPSCs) exhibited greater than 95% cell viability. In addition, as the DDMp concentration increased, odontogenic differentiation of DPSCs was significantly enhanced. Finally, we demonstrated that cellular constructs with 3D patient-specific shapes and clinically relevant sizes could be fabricated through co-printing of polycaprolactone and DPSC-laden DDMp bio-ink.

Fluorescence-linked immunosorbent assay (FLISA) is a commonly used, quantitative technique for detecting biochemical based on antigen–antibody binding reactions using a well-plate platform. With the developments in the manufacturing technology of microfluidic systems, FLISA can be implemented onto microfluidic disk platforms, which allows the detection of trace biochemical with high resolutions. Apart from requiring a lower proportion of reagent (1/10), this method also reduces the time required for the entire process to less than an hour. The incubation process involves antigen–antibody binding reactions as well as the binding of fluorogenic substrates to target proteins. The protocol for FLISA on a microfluidic platform necessitates the appropriate execution of liquid reagent movements during each step in order to ensure sufficient binding reactions. Herein, we propose a novel microfluidic disk comprising a 3D incubation chamber. Vascular endothelial growth factor as concentration with ng mL-1 is detected sequentially using a benchtop process employing this 3D microfluidic disk. The 3D microfluidic disk is implemented without requiring manual intervention or additional procedures for liquid control. During the incubation process, microbead movement is controlled through centrifugal force, generated due to disk rotation, and gravitational force via bead sedimentation on the sloped floor of the chamber.

Photothermal therapy (PTT) requires tight thermal dose control to achieve tumor ablation with minimal thermal injury on surrounding healthy tissues. In this study, we proposed a real-time closed-loop system for monitoring and controlling the temperature of PTT using a non-contact infrared thermal sensor array and an artificial neural network (ANN) to induce a predetermined area of thermal damage on the tissue. A cost-effective infrared thermal sensor array was used to monitor the temperature development for feedback control during the treatment. The measured and predicted temperatures were used as inputs of fuzzy control logic controllers that were implemented on an embedded platform (Jetson Nano) for real-time thermal control. Three treatment groups (continuous wave = CW, conventional fuzzy logic = C-Fuzzy, and ANN-based predictive fuzzy logic = P-Fuzzy) were examined and compared to investigate the laser heating performance and collect temperature data for ANN model training. The ex vivo experiments validated the efficiency of fuzzy control with temperature method on maintaining the constant interstitial tissue temperature (80 ± 1.4 °C) at a targeted surface of the tissue. The linear relationship between coagulation areas and the treatment time was indicated in this study, with the averaged coagulation rate of 0.0196 cm2/s. A thermal damage area of 1.32 cm2 (diameter ∼1.3 cm) was observed under P-Fuzzy condition for 200 s, which covered the predetermined thermal damage area (diameter ∼1 cm). The integration of real-time feedback temperature control with predictive ANN could be a feasible approach to precisely induce the preset extent of thermal coagulation for treating papillary thyroid microcarcinoma.

Endoscopic submucosal dissection (ESD) is clinically used to remove early gastric cancer in stomach. The aim of the current study is to examine a therapeutic capacity of pulsed Ho:YAG laser for the development of laser-assisted ESD under various surgical parameters. Ex vivo porcine stomach tissue was ablated with 1-J Ho:YAG pulses at 10 Hz at different number of treatments (NT = 1, 2, and 3) and treatment speeds (TS = 0.5, 1, and 2 mm/s) without and with saline injection. Regardless of saline injection, straight tissue ablation showed that ablation depth increased with increasing NT and decreasing TS. At NT = 3 and TS = 0.5 mm/s, no saline injection yielded the maximum ablation depth (3.4 ± 0.3 mm), partially removing muscularis propria. However, saline injection confined the tissue ablation within a submucosal layer (2.1 ± 0.3 mm). Thermal injury was found to be 0.7~1.1 mm in the adjacent tissue with superficial carbonization. Circular tissue ablation (2 cm in diameter) at NT = 3 and TS = 0.5 mm/s presented that no saline injection yielded a reduction in the lesion area, whereas saline injection maintained the ablated lesion area. Histological analysis revealed that unlike no saline injection, saline injection ablated the entire mucosal layer without perforation in the muscular propria. The pulsed Ho:YAG laser can be a potential surgical tool for clinical ESD to incise a target lesion without adverse perforation. Further investigations will validate the efficacy and safety of the Ho:YAG laser-assisted ESD in in vivo porcine stomach models for clinical translation.

A microfluidic circuit on a disk platform, also known as lab-on-a-disk, is an integrated system for automated high-throughput screening for biochemical analysis. The microfluidic circuit on a disk performs biochemical analysis through sequential processes such as filtration, separation, detection, and synthesis of reagents. Sequential processes in microfluidic circuits operate through the systematically linked components, which include channels, valves, and chambers. The microchannels should have micrometer-scale for precise micro-volume liquid control in the microfluidic circuit on a disk. However, it is difficult to also consider productivity in the traditional technology. In addition, as the channel length increases, much effort is required to construct the components of the microfluidic circuit in the limited space of the disk. 3D printing is drawing attention as a microfluidic channel fabrication technique in order to overcome the physical limitations of the traditional methods. A new concept of a 3D slope valve has been developed, which performs precise and sequential micro-volume liquid control through centrifugal and gravitational forces. Micro-volumes of liquids in a slope valve-equipped circuit are controlled over a wide range of angular velocities through the control of the valve geometry, types of liquid and volume. For sequential micro-volume of liquid control, three lines of assembled modules are connected to a microfluidic circuit. In the microfluidic circuit with slope valves, the detection of fluorescent dye tagged-VEGF is possible through sequential mixing and reaction processes. As a result, micro-volume liquid is successfully controlled with high accuracy using the 3D microfluidic circuit with a slope valve.

3D printed biomaterials have been extensively investigated and developed in the field of bone regeneration related to clinical issues. However, specific applications of 3D printed biomaterials in different dental areas have seldom been reported. In this study, we aimed to and successfully fabricated 3D poly (lactic-co-glycolic acid)/&beta, tricalcium phosphate (3D-PLGA/TCP) and 3D &beta, tricalcium phosphate (3D-TCP) scaffolds using two relatively distinct 3D printing (3DP) technologies. Conjunctively, we compared and investigated mechanical and biological responses on human dental pulp stem cells (hDPSCs). Physicochemical properties of the scaffolds, including pore structure, chemical elements, and compression modulus, were characterized. hDPSCs were cultured on scaffolds for subsequent investigations of biocompatibility and osteoconductivity. Our findings indicate that 3D printed PLGA/TCP and &beta, tricalcium phosphate (&beta, TCP) scaffolds possessed a highly interconnected and porous structure. 3D-TCP scaffolds exhibited better compressive strength than 3D-PLGA/TCP scaffolds, while the 3D-PLGA/TCP scaffolds revealed a flexible mechanical performance. The introduction of 3D structure and &beta, TCP components increased the adhesion and proliferation of hDPSCs and promoted osteogenic differentiation. In conclusion, 3D-PLGA/TCP and 3D-TCP scaffolds, with the incorporation of hDPSCs as a personalized restoration approach, has a prospective potential to repair minor and critical bone defects in oral and maxillofacial surgery, respectively.

A programmable drug delivery system can control the release rate of a drug. It can minimize side effects while maximizing therapeutic effects. In this research, we investigated the feasibility of producing a programmable drug delivery system using 3D printing technology. A capsule with a micro-orifice and a drug-laden hydrogel was designed. The designed system was then fabricated by the printing process using polycaprolactone and hydrogel. The printed drug delivery system was immersed in PBS at 37°C and the number of molecules released was measured thorough colorimetric analysis. The effect of diameter and length of the micro-orifice and concentration of the hydrogel on drug release characteristics was then determined. The initial burst release rate was found to be increased with increasing orifice size. Increasing the length of the orifice linearly delayed the start time of drug release. At length of 600 μm and 1,200 μm, drug release was initiated after 36 h and 72 h for, respectively. When the concentration of hydrogel was increased, drug release rate tended to decrease. These results successfully confirmed that a drug delivery system with controlled release rate and initiation time could be manufactured using 3D printing technology.

Recently, decellularized extracellular matrix-based bio-ink (dECM bio-ink) derived from animal organs is attracting attention because of its excellent biocompatibility. However, its poor 3D printability and weak mechanical properties remain a challenge. Here, we developed a new dECM bio-ink with enhanced 3D printability and mechanical properties. dECM micro-particles of about 13.4 μm in size were prepared by decellularizing a porcine liver followed by freeze-milling. The new bio-ink, named as dECM powder-based bio-ink (dECM pBio-ink), was prepared by loading the dECM micro-particles into a gelatin mixture. The usefulness of the dECM pBio-ink was evaluated by assessing its mechanical properties, printability, and cytocompatibility. The results showed that its mechanical properties and 3D printability were greatly improved. Its elastic modulus increased by up to 9.17 times that of the conventional dECM bio-ink. Micro-patterns with living cells were successfully achieved with 93% cell viability. Above all, the new bio-ink showed superior performance in stacking of layers for 3D printing, whereas the conventional bio-ink could not maintain its shape. Finally, we demonstrated that the dECM pBio-ink possessed comparable cytocompatibility with the conventional dECM bio-ink through in vitro tests with endothelial cells and primary mouse hepatocytes.

Nanohydroxyapatite (nHA) is a widely accepted bone substitute material due to its biocompatibility and intrinsic osteoconductive properties. For various tissue-engineered applications including 3D-printing fabrication of bone substitutes, composite scaffolds combining calcium phosphate such as nHA with synthetic polymer such as polycaprolactone (PCL) have been extensively explored to enhance the mechanical and physiochemical properties. In this study, 3D-printed PCL/nHA scaffolds were developed using mechanical extrusion-based 3D bioprinter. Scaffold morphology, chemical composition, mechanical strength, cell proliferation, and mineralization were quantitatively analyzed at various concentrations of nHA (0, 10, 20 and 30 wt%). The experimental results suggest essential data to optimize mechanical properties, printability, cellular interactions, and osteoconductivity of 3D-printed PCL/nHA composite scaffolds.

Numerous researchers have studied 3D hybrid bioprinting technology, as it appears to be a viable option for producing cellular constructs with clinical relevance. This technology uses a co-printing process with high strength bio-plastics and cell-laden bio-inks. The bio-inks used in this technology should be easily printable and provide good biological environment for artificial tissue regeneration. In this research, we present a gelatin-based bio-ink for 3D hybrid bioprinting. We prepared a variety of gelatin mixtures and evaluated them in terms of their printability. We also investigated the effects of using hyaluronan and glycerol as additives. The results showed that hyaluronan and glycerol enhanced the spatial resolution and uniformity of the printed patterns. We determined the optimal composition for the bio-ink and then conducted 2D and 3D cell patterning tests. The results showed that our bio-ink can produce a line width of approximately 200μm, and multiple types of cells can be positioned precisely in 3D structures. We also conducted a cytocompatibility test with NIH3T3 fibroblast. This test showed the processability of our bio-ink with living cells. Finally, we printed an actual-size, human ear-shaped construct. These experiments suggest that the proposed gelatin-based bio-ink is well suited for applications to 3D hybrid bioprinting technology.

Currently, almost 70% of the world’s population occupies urban areas. Owing to the high population density in these regions, they are exposed to various types of air pollutants. Fine particle air pollutants (&lt, 2.5 μm) can easily invade the human respiratory system, causing health issues. For fine particulate matter filtration, the use of a face mask filter is efficient, however, its use is accompanied by a high-pressure drop, making breathing difficult. Electrostatic interactions in the filter of the face mask constitute the dominant filtration mechanism for capturing fine particulate matter, these masks are, however, significantly weakened by the high humidity in exhaled breath. In this study, we demonstrate that a filter with an electrostatically rechargeable structure operates with normal breathing air power. In our novel face mask, a filter membrane is assembled by layer-by-layer stacking of the electrospun PVDF nanofiber mat formed on a nylon mesh. Tribo/piezoelectric characteristics via multilayer structure enhance filtration performance, even under air-powered filter bending taken as a normal breathing condition. The air gap between nanofiber and mesh layers increases air diffusion time and preserves the electrostatic charges within the multi-layered nanofiber filter membrane under humid air penetration, which is advantageous for face mask applications.

This study aims to demonstrate the feasibility of cylindrical interstitial laser ablation (CILA) in porcine pancreatic tissue to develop a EUS-guided PC ablation technique with enhanced safety. A diffusing applicator created a uniformly symmetrical laser ablation in pancreatic tissue. Ex vivo tests presented that both ablation thickness and volume increased linearly with the applied power (R2 = 0.96 and 0.90, respectively) without carbonization and fiber degradation. The numerical simulations matched well with the experimental results in terms of temperature development and thermal damage (deviation of ≤ 15%). In vivo tests with EUS confirmed easy insertion and high durability of the diffusing applicator. EUS-guided CILA warranted a feasible therapeutic capacity of ablating in vivo pancreatic tissue. The proposed EUS-guided CILA can be a feasible therapeutic approach to treat PC with predictable thermal ablation and enhanced safety.

In the current study, a multi-wavelength light-emitting diode (LED)-integrated CMOS imaging device was developed to investigate the effect of various wavelengths on multiple color characterization. Various color pigments (black, red, green, and blue) were applied on both white paper and skin phantom surfaces for quantitative analysis. The artificial skin phantoms were made of polydimethylsiloxane (PDMS) mixed with coffee and TiO2 powder to emulate the optical properties of the human dermis. The customized LED-integrated imaging device acquired images of the applied pigments by sequentially irradiating with the LED lights in the order of white, red, green, and blue. Each color pigment induced a lower contrast during illumination by the light with the equivalent color. However, the illumination by light with the complementary (opposite) color increased the signal-to-noise ratio by up to 11-fold due to the formation of a strong contrast (i.e., red LED = 1.6 ± 0.3 vs. green LED = 19.0 ± 0.6 for red pigment). Detection of color pigments in conjunction with multi-wavelength LEDs can be a simple and reliable technique to estimate variations in the color pigments quantitatively.

3D printing technologies have gotten an attention as a viable option for future manufacturing. Among them, FDM is the most popular one because it is inexpensive and can process with multiples materials. Layered surface, that has high roughness, is obtained with the technology due to layer-by-layer based process. This result highly decreases value of the final product. Various methods for postprocessing were proposed to achieve fine surface. Among them, vapor smoothing process is one of powerful methods because of its cost-effectiveness and usefulness. However, this process could affect mechanical property of the printed structure. In this study, we investigated the effect of the vapor smoothing technique with 3D printed structures in terms of thermal-dependent mechanical property. ABS structure was fabricated with FDM and applied into the post-processing. Then, temperature-dependent storage modulus and tan δ of the structure were measured with dynamic mechanical analysis (DMA) in the variation of amount of acetone. The results showed that the process highly affects to the thermal stability. Below 50°C, any differences were not observed. However, lower modulus and higher tan δ were shown in the higher temperature. This experiment provides very useful data for FEM simulation to predict mechanical property of a 3D printed structure.

To develop flexible transparent electrodes, an ink fabricated with silver nanowires (AgNWs) was coated on a polyethylene terephthalate substrate using a roll-to-roll slot die machine. The AgNW used in the manufacturing of the transparent electrode is a highly transparent conductive material that is very close to commercialization due to its low sheet resistance, low heat treatment temperature, and high transmittance. An AgNW ink was optimized for the slot die process, which was prepared using the optimized formulation with AgNWs, solvent, and dispersant. As a result, high-quality transparent conductive films were successfully manufactured with 32–94 Ω sq−1 of sheet resistance, 1.3–3.2 of haze and 86.2–92% transmittance with a width of 300 mm. To verify the possibilities in optoelectronic applications, organic solar cells were fabricated with the AgNW mesh transparent electrode and showed a good performance of 7.65% efficiency, which was better than the result obtained using an indium tin oxide-based electrode.

For high-throughput flexible electronic devices to be ready for the market, their transparent conductive electrodes (TCEs) should show stable working performance during folding conditions and have a long operating life. In this study, TCEs were produced by over-coating silver nanowire (AgNW) electrodes with graphene oxide (GO). The GO/AgNW electrodes showed an outstanding sheet resistance value of 18 Ω−1, 87% transmittance, mechanical stability, and excellent long-term stability. Furthermore, the GO film wrapped around the AgNWs, which improved the inter-nanowire junction resistance and lowered the surface roughness without any heat treatments or high-force pressing processes. Flexible P3HT:PC60BM- and PTB7:PC70BM-based organic solar cells (OSCs) were produced using the GO/AgNW transparent electrodes on a flexible polyethylene terephthalate substrate. The GO/AgNW electrode exhibited a higher optical absorption in all the OSCs compared to those of the indium tin oxide (ITO) electrodes and showed a high short circuit current of 3 mA cm−2. Consequently, the fabricated OSCs showed a 7% higher efficiency than the ITO electrodes. In addition, after 50 bending tests, the efficiency of the GO/AgNW electrodes changed less than 3%. Thus, the GO/AgNW electrodes showed enhanced results in terms of resistance and durability compared to conventional transparent electrodes, including ITO-based electrodes.

Macrophages are excellent imaging targets for detecting atherosclerotic plaques as they are involved in all the developmental stages of atherosclerosis. However, no imaging technique is currently capable of visualizing macrophages inside blood vessel walls. The current study develops an intravascular ultrasonic-photoacoustic (IVUP) imaging system combined with indocyanine green (ICG) as a contrast agent to provide morphological and compositional information about the targeted samples. Both tissue-mimicking vessel phantoms and atherosclerotic plaque-mimicking porcine arterial tissues are used to demonstrate the feasibility of mapping macrophages labeled with ICG by endoscopically applying the proposed hybrid technique. A delay pulse triggering technique is able to sequentially acquire photoacoustic (PA) and ultrasound (US) signals from a single scan without using any external devices. The acquired PA and US signals are used to reconstruct 2D cross-sectional and 3D volumetric images of the entire tissue with the ICG-loaded macrophages injected. Due to high imaging contrast and sensitivity, the IVUP imaging vividly reveals structural information and detects the spatial distribution of the ICG-labeled macrophages inside the samples. ICG-assisted IVUP imaging can be a feasible imaging modality for the endoscopic detection of atherosclerotic plaques.

Electrospinning is a nano-scale fiber production method with various polymer materials. This technique allows simple fiber diameters control by changing the physical conditions such as applied voltage and polymer solution viscosity during the fabrication process. The electrospun polymer fibers form a thin porous film with high surface area to volume ratio. Due to these unique characteristics, it is widely used for many application fields such as photocatalyst, electric sensor, and antibacterial scaffold for tissue engineering. Filtration is one of the main applications of electrospun polymer fibers for specific application of filtering out dust particles and dehumidification. Most polymers which are commonly used in electrospinning are hard to perform the filtering and dehumidification simultaneously because of their low hygroscopic property. To overcome this obstacle, the desiccant polymers are developed such as polyacrylic acid and polysulfobetaine methacrylate. However, the desiccant polymers are generally expensive and need special solvent for electrospinning. An alternating way to solve these problems is mixing desiccant material like zeolite in polymer solution during an electrospinning process. In this study, the free surface energy characteristics of electrospun polyvinylidene fluoride (PVDF) film with various zeolite concentrations are investigated to control the hygroscopic property of general polymers. Fundamental physical property of wettability with PVDF shows hydrophobicity. The electrospun PVDF film with small weight ratio with higher than 0.1% of zeolite powder shows diminished contact angles that certifying the wettability of PVDF can be controlled using desiccant material in electrospinning process. To quantify the surface energy of electrospun PVDF films, sessile water droplets are introduced on the electrospun PVDF film surface and the contact angles are measured. The contact angles of PVDF film are 140° for without zeolite and 80° for with 5 wt% of zeolite respectively. As a result, the surface energy of PVDF film can be controlled by embedding zeolite particles in electrospinning process and applied to filtration application of dust filtering and dehumidification simultaneously with low manufacturing cost.

Background Temperature monitoring during high-intensity focused ultrasound (HIFU) therapy on tissue is essential to regulate the degree of thermal coagulation and to achieve the desired treatment outcomes eventually. The aim of the current study was to design and investigate the feasibility of a proportional–integral–derivative (PID) temperature controller-integrated portable HIFU driver for thermal coagulation. Methods A portable HIFU driver was designed and operated at a maximum output voltage of 50 V with pulse-width modulation signals at 2 MHz. The temperature of ex vivo bovine liver tissue was monitored using a K-type thermocouple during the 2-MHz HIFU exposure. Results The tissue temperature was maintained at 60 °C using a PID controller-integrated HIFU driver that modulated the output voltage during the 300-s HIFU exposure. The ex vivo testing demonstrated that the tissue temperature at the focal point approached the chosen temperature, i.e., 60 °C, within 70 s. The temperature was maintained with a deviation of less than 4 °C until the HIFU driver voltage was turned off at 300 s. Conclusions The designed PID controller-integrated HIFU driver can be used as a small portable tool to regulate the tissue temperature in real time and achieve thermal coagulation via HIFU sonication.

During a thin film application, the surface of the coating liquid applied to the substrate becomes uneven because of the geometry of the substrate, viscosity of the coating liquid, surface tension, and its contact angle with the substrate. The surface is particularly uneven at the edge corner portion of the substrate and is thicker than the average coating thickness. This study used the volume-of-fluid (VOF) method to examine the surface unevenness of the coating liquid in terms of the contact angle of the substrate surface and sides. After the coating liquid was evenly applied to the substrate, the maximum height of the uneven region of the coating liquid at the edge of the substrate increased as time passed. The point of maximum height moved away from the edge corner portion of the substrate. The coating liquid applied to the substrate with a contact angle less than 90&deg, exhibited a pinning effect in which the contact point was fixed at the edge. The surface unevenness was more pronounced in the absence of the pinning effect than in its presence, due to the effects of the viscosity of the coating fluid and the surface energy of the substrate.

Electric fields are widely used for controlling liquids in various research fields. To control a liquid, an alternating current (AC) electric field can offer unique advantages over a direct current (DC) electric field, such as fast and programmable flows and reduced side effects, namely the generation of gas bubbles. Here, we demonstrate one-directional flow along carbon nanotube nanowires under an AC electric field, with no additional equipment or frequency matching. This phenomenon has the following characteristics: First, the flow rates of the transported liquid were changed by altering the frequency showing Gaussian behaviour. Second, a particular frequency generated maximum liquid flow. Third, flow rates with an AC electric field (approximately nanolitre per minute) were much faster than those of a DC electric field (approximately picolitre per minute). Fourth, the flow rates could be controlled by changing the applied voltage, frequency, ion concentration of the solution and offset voltage. Our finding of microfluidic control using an AC electric field could provide a new method for controlling liquids in various research fields.

Simple Summary Colorectal cancer is one of the most common cancers and the third leading cause of cancer-related deaths in the United States. As a non- or minimally invasive cancer treatment, photothermal therapy (PTT) has been widely used to generate irreversible thermal injuries in tumors. However, conventional PTT employs an end-firing flat fiber to deliver laser energy, leading to the incomplete removal of tumor tissues due to an uneven beam distribution over the tumor surface. Multi-lens arrays (MLA) generate multiple micro-beams to uniformly distribute laser energy on the tissue surface. Therefore, the application of MLA for PTT in cancer affords a spatially enhanced distribution of micro-beams and laser-induced temperature in the tumor. The purpose of the current study is to computationally and experimentally demonstrate the therapeutic benefits of MLA-assisted fractional PTT on colorectal cancer, in comparison to flat fiber-based PTT. Abstract Conventional photothermal therapy (PTT) for cancer typically employs an end-firing flat fiber (Flat) to deliver laser energy, leading to the incomplete treatment of target cells due to a Gaussian-shaped non-uniform beam profile. The purpose of the current study is to evaluate the feasibility of multi-lens arrays (MLA) for enhanced PTT by delivering laser light in a fractional micro-beam pattern. Computational and experimental evaluations compare the photothermal responses of gelatin phantoms and aqueous dye solutions to irradiations with Flat and MLA. In vivo colon cancer models have been developed to validate the therapeutic capacity of MLA-assisted irradiation. MLA yields 1.6-fold wider and 1.9-fold deeper temperature development in the gelatin phantom than Flat, and temperature monitoring identified the optimal treatment condition at an irradiance of 2 W/cm2 for 180 s. In vivo tests showed that the MLA group was accompanied by complete tumor eradication, whereas the Flat group yielded incomplete removal and significant tumor regrowth 14 days after PTT. The proposed MLA-assisted PTT spatially augments photothermal effects with the fractional micro-beams on the tumor and helps achieve complete tumor removal without recurrence. Further investigations are expected to optimize treatment conditions with various wavelengths and photosensitizers to warrant treatment efficacy and safety for clinical translation.

Coaxial type piezoelectric energy generator (C-PEG) nanofiber was fabricated by a self-designed continuous electrospinning deposition system. Piezoelectric PVDF-TrFE nanofiber as an electroactive material was electrospun at a discharge voltage of 9–12 kV onto a simultaneously rotating and transverse moving Cu metal wire at an angular velocity of ω g = 60–120 RPM. The piezoelectric coefficient d33 of the PVDF-TrFE nanofiber was approximately −20 pm V−1. The generated output voltage (V G) increased according to the relationship exp(-α P) (α = 0.41– 0.57) as the pressure (P) increased from 30 to 500 kpa. The V G values for ten and twenty pieces of C-PEG were V G = 3.9 V and 9.5 V at P = 100 kpa, respectively, relatively high output voltages compared to previously reported values. The high V G for the C-PEG stems from the fact that it can generate a fairly high V G due to the increased number of voltage collection points compared to a conventional two-dimensional (2-dim) capacitor type of piezoelectric film or fiber device. C-PEG yarn was also fabricated via the dip-coating of a PDMS polymer solution, followed by winding with Ag-coated nylon fiber as an outer electrode. The current and power density of ten pieces of C-PEG yarn were correspondingly 22 nA cm−2 and 8.6 μW cm−3 at V G = 1.97 V, higher than previously reported values of 5.54 and 6 μW cm−3. The C-PEG yarn, which can generate high voltage compared to the conventional film/nanofiber mat type, is expected to be very useful as a wearable energy generator system.

In the present study, we fabricated an epidermal growth factor receptor (EGFR)-conjugated hydrogel to promote wound healing in cold restraint-induced gastric ulceration on burn wounds targeting collagen and inflammatory cells for the treatment of burns and gastric ulcers. Cytotoxicity and cell proliferation assays demonstrated good biocompatibility of hydrogel as a suitable extracellular matrix for targeted cells and support for regenerative cell growth. These findings were confirmed by staining methods. In vitro wound healing was confirmed cell migration in the targeted cells. The effect of the EGFR-H was investigated in cold restraint-induced gastric ulcers in rats, where the treatment was started immediately after ulcer induction. In the in vivo experiment, the EGFR-H demonstrated enhanced ulcer healing ability and less scarring compared to the hydrogel alone and controls. Thus, EGFR-H promotes healing of cold restraint-induced gastric ulcer via EGFR conjugated with a hydrogel. The present study demonstrates a novel pathway to fabricate hydrogels as suitable wound dressing biomaterials to improve deep partial thickness burn wound healing and prevent scar formation when aided by laser therapy.

Liquid film thickness is an important parameter for predicting evaporation and condensation heat transfer performance of two-phase slug flow in a capillary tube. Under flow boiling condition, the bubble of two-phase slug flow is elongated and accelerated. In the present study, the effect of acceleration on the liquid film thickness of unsteady two-phase slug flow is theoretically and experimentally investigated. It is first theoretically found that the accelerated slug flow is affected by the dimensionless numbers of capillary number (Ca), Weber number (We), and Bond number (Bo). The relation of the dimensionless liquid film thickness with the capillary number, Weber number, and Bond number for unsteady accelerated slug flows was obtained. The liquid film thicknesses of two-phase slug flows under acceleration condition were directly measured using laser focus displacement metering technique. Circular capillary tube with inner diameter of 1 mm was used for the test tube, and water, ethanol and FC-40 were used as working fluids. The novel prediction correlation of liquid film thickness for accelerated slug flows was proposed and it well predicts all the experimental data for all conditions. As the Bond number increases, the liquid film thicknesses are gradually shifted in the direction of decreasing film thickness due to acceleration effect. At a fixed capillary number, initial liquid film thickness becomes thinner with increasing Bond number.

This study develops an energy modulation technique to attain a constant interstitial tissue temperature and to induce the predetermined thermal coagulation without carbonization in tissue. An optical diffuser was employed to deliver 1064 nm light to the biological tissue. The combined mode maintained the interstitial temperature at 70 ℃ for longer durations compared to the continuous wave mode. Coagulation volumes increased linearly with the time and met the predetermined treatment volume range (0.32–0.52 cm3) after the combined treatment for 100 s. The combined modulation can be a feasible modality to induce the predetermined extent of thermal coagulation for treating papillary thyroid microcarcinoma.

In the study, a new method to enhance the performance of a thermoelectric generator (TEG) device by utilizing the water-film evaporative cooling is proposed. An experimental device was constructed by incorporating a water-film cooling pond with a commercially available TEG. Experiments were performed to investigate the effects of the main operating conditions (ambient temperature Tamb was 25 °C), TEG hot-side temperature (TH = 50–100 °C), ambient relative humidity (RH = 15–90%), and water-film thickness (twater = 1–9 mm) on the TEG output performance. Additionally, the output performance of TEG under different cooling methods was compared. A TEG prototype device was constructed to generate electricity/steam using seawater evaporation cooling without external electrical energy. The results indicated that TEG hot-side temperature and water-film thickness significantly affected output performance. However, the ambient relative humidity did not considerably affect TEG output performance. Given TEG hot-side temperature TH = 100 °C, ambient relative humidity RH = 15%, the TEG prototype device-generated open-circuit voltage of Uopen = 1.55 V, maximum output power of Pmax = 290.32 mW, and a steam generation rate of 9.82 mg/s. The results showed that evaporative cooling is an innovative method to improve the performance of TEG.