Piezoelectric energy harvesters (PEHs) aim to generate sufficient power to operate targeting device from the limited ambient energy. PEH includes mechanical‐to‐mechanical, mechanical‐to‐electrical, ...and electrical‐to‐electrical energy conversions, which are related to PEH structures, materials, and circuits, respectively; these should be efficient for increasing the total power. This critical review focuses on PEH structures and materials associated with the two major energy conversions to improve PEH performance. First, the resonance tuning mechanisms for PEH structures maintaining continuous resonance, regardless of a change in the vibration frequency, are presented. Based on the manual tuning technique, the electrically‐ and mechanically‐driven self‐resonance tuning (SRT) techniques are introduced in detail. The representative SRT harvesters are summarized in terms of tunability, power consumption, and net power. Second, the figure‐of‐merits of the piezoelectric materials for output power are summarized based on the operating conditions, and optimal piezoelectric materials are suggested. Piezoelectric materials with large kij, dij, and gij values are suitable for most PEHs, whereas those with large kij and Qm values should be used for on‐resonance conditions, wherein the mechanical energy is directly supplied to the piezoelectric material. This comprehensive review provides insights for designing efficient structures and selection of proper piezoelectric materials for PEHs.
The piezoelectric energy harvester (PEH) aims to generate sufficient power to operate targeting devices from limited ambient energy. PEHs include mechanical‐to‐mechanical, mechanical‐to‐electrical, and electrical‐to‐electrical energy conversion, which are related to the structures, materials, and circuits, respectively; these should be efficient for increasing total power. Recent studies on self‐resonance tuning mechanisms for PEH structures and the figure‐of‐merit for piezoelectric materials are reviewed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Reducing the impedance of a triboelectric nanogenerator (TENG) without power loss is crucial for enhancing its energy conversion efficiency and overall performance. In this paper, a novel signal ...management structure, based on a newly designed sliding‐mode TENG, aimed at effectively reducing impedance by converting narrow, instantaneous signals into broader ones is presented. This transformation is accomplished by adding a grounded electrode connected to a high‐inductive inductor and fine‐tuning the parasitic capacitance of the dielectric material. Utilizing a highly resistive material like P(VDF–TrFE), a significant improvement in the TENG's performance is achieved, resulting in an increase of output power to 0.352 mW and a decrease in impedance from 3.2 to 0.3 MΩ. This results in a threefold increase in charging speed, which can be attributed to the reduced charge loss and improved matching at lower impedance. Based on these promising findings, the enhanced TENG is successfully connected to power a system for electrochemical CO2 reduction for CO production. This system effectively reduces the required electrochemical reduction potential by ≈15% under real environments.
A novel sliding‐mode TENG designed to enhance energy conversion efficiency is described by implementing a high‐inductive inductor and optimizing the parasitic capacitance of the dielectric. The TENG achieves a substantial performance boost to 0.352 mW with a decrease in impedance from 3.2 to 0.3 MΩ, resulting in a threefold increase in charging speed. It is successfully applied to power an electrochemical CO2 reduction system, reducing the required electrochemical reduction potential by ≈15% in real environments.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Dynamic manipulation of supramolecular self‐assembled structures is achieved irreversibly or under non‐physiological conditions, thereby limiting their biomedical, environmental, and catalysis ...applicability. In this study, microgels composed of azobenzene derivatives stacked via π–cation and π–π interactions are developed that are electrostatically stabilized with Arg–Gly–Asp (RGD)‐bearing anionic polymers. Lateral swelling of RGD‐bearing microgels occurs via cis‐azobenzene formation mediated by near‐infrared‐light‐upconverted ultraviolet light, which disrupts intermolecular interactions on the visible‐light‐absorbing upconversion‐nanoparticle‐coated materials. Real‐time imaging and molecular dynamics simulations demonstrate the deswelling of RGD‐bearing microgels via visible‐light‐mediated trans‐azobenzene formation. Near‐infrared light can induce in situ swelling of RGD‐bearing microgels to increase RGD availability and trigger release of loaded interleukin‐4, which facilitates the adhesion structure assembly linked with pro‐regenerative polarization of host macrophages. In contrast, visible light can induce deswelling of RGD‐bearing microgels to decrease RGD availability that suppresses macrophage adhesion that yields pro‐inflammatory polarization. These microgels exhibit high stability and non‐toxicity. Versatile use of ligands and protein delivery can offer cytocompatible and photoswitchable manipulability of diverse host cells.
Remote control of microgels via tissue‐penetrative light is demonstrated. Near‐infrared‐light‐upconverted ultraviolet light stimulates in situ swelling of RGD‐bearing microgels that increases RGD availability, thereby facilitating macrophage adhesion linked with pro‐regenerative polarization. Visible light induces the deswelling of RGD‐bearing microgels that decreases RGD availability that suppresses macrophage adhesion that yields pro‐inflammatory polarization.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Recent advances in lithography technology and the spread of 3D printers allow us a facile fabrication of special materials with complicated microstructures. The materials are called "designed ...materials" or "architectured materials" and provide new opportunities for material development. These materials, which owing to their rationally designed architectures exhibit unusual properties at the micro- and nano-scales, are being widely exploited in the development of modern materials with customized and improved performance. Meta-materials are found to possess superior and unusual properties as regards static modulus (axial stress divided by axial strain), density, energy absorption, smart functionality, and negative Poisson's ratio (NPR). However, in spite of recent developments, it has only been feasible to fabricate a few such meta-materials and to implement them in practical applications. Against such a backdrop, a broad review of the wide range of cellular auxetic structures for mechanical metamaterials available at our disposal and their potential application areas is important. Classified according to their geometrical configuration, this paper provides a review of cellular auxetic structures. The structures are presented with a view to tap into their potential abilities and leverage multidimensional fabrication advances to facilitate their application in industry. In this review, there is a special emphasis on state-of-the-art applications of these structures in important domains such as sensors and actuators, the medical industry, and defense while touching upon ways to accelerate the material development process.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Since recurrence and metastasis of pancreatic cancer has a worse prognosis, chemotherapy has been typically performed to attack the remained malignant cells after resection. However, it is difficult ...to achieve the therapeutic concentration at the tumor site with systemic chemotherapy. Numerous local drug delivery systems have been studied to overcome the shortcomings of systemic delivery. However, because most systems involve dissolution of the drug within the carrier, the concentration of the drug is limited to the saturation solubility, and consequently cannot reach the sufficient drug dose. Therefore, we hypothesized that 3D printing of a biodegradable patch incorporated with a high drug concentration would provide a versatile shape to be administered at the exact tumor site as well as an appropriate therapeutic drug concentration with a controlled release. Here, we introduce the 3D-printed patches composed of a blend of poly(lactide-co-glycolide), polycaprolactone, and 5-fluorouracil for delivering the anti-cancer drug in a prolonged controlled manner and therapeutic dose. 3D printing technology can manipulate the geometry of the patch and the drug release kinetics. The patches were flexible, and released the drug over four weeks, and thereby suppressed growth of the subcutaneous pancreatic cancer xenografts in mice with minimized side effects. Our approach reveals that 3D printing of bioabsorbable implants containing anti-cancer drugs could be a powerful method for an effective local delivery of chemotherapeutic agents to treatment of cancers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Extracellular matrix (ECM) proteins containing cell‐attachable Arg‐Gly‐Asp (RGD) sequences exhibit variable bridging and non‐bridging in fibronectin‐collagen and laminin‐collagen complexes that can ...regulate inflammation, tissue repair, and wound healing. In this study, linking molecule‐mediated conjugation of 1D magnetic nanocylinders (MNCs) to material surfaces pre‐decorated with gold nanospheres (GNSs) is performed, thereby yielding RGD‐coated MNCs (RGD‐MNCs) over RGD‐coated GNSs (RGD‐GNSs) in a non‐bridging state. The RGD‐MNCs are drawn closer to the RGD‐GNSs via magnetic field‐mediated compression of the linking molecules to establish the bridging between them. Relative proportion of the RGD‐MNCs to the RGD‐GNSs is optimized to yield effective remote stimulation of integrin binding to variably bridged RGDs similar to that of invariably bridged RGDs used as a control group. Remote manipulation of the RGD bridging facilitates the attachment structure assembly of macrophages that leads to pro‐healing/anti‐inflammatory phenotype acquisition. In contrast, the non‐bridged RGDs inhibited macrophage attachment that acquired pro‐inflammatory phenotypes. The use of various nanomaterials in constructing heterogeneous RGD‐coated materials can further offer various modes in remote switching of RGD bridging and non‐bridging to understand dynamic integrin‐mediated modulation of macrophages that regulate immunomodulatory responses, such as foreign body responses, tissue repair, and wound healing.
RGD‐coated materials of 1D magnetic RGDs over non‐magnetic RGDs are developed to enable remote manipulation of variable RGD bridging. Remote control of RGD bridging and non‐bridging reversibly regulates integrin binding and adhesion structure assembly that modulate the functional polarizations for pro‐inflammatory or pro‐healing immunoregulation of host macrophages.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Background and Aims Preoperative biliary drainage (PBD) with stent placement has been commonly used for patients with malignant biliary obstruction. In PBD, the placement of fully covered ...self-expandable metal stents (FCSEMSs) may provide better patency duration and a lower incidence of cholangitis compared with plastic stents. We aimed to evaluate which type of stent showed better outcomes in PBD. Methods In this multicenter, prospective randomized trial, we compared PBD with FCSEMSs versus plastic stents in 86 patients with malignant biliary obstruction between January 2012 and December 2014. Patients with obstructive jaundice were randomly assigned to undergo PBD either with plastic stents or FCSEMS placement. Results Baseline characteristics were not significantly different between the 2 groups. Endoscopic stent placement was technically successful in all patients. Procedure-related adverse events were not significantly different between the 2 groups (plastic vs FCSEMS group; 16.3% vs 16.3%, P = 1.0). Reintervention was required in 16.3% of the plastic stent group and 14.0% of the FCSEMS group ( P = .763). The interval to surgery after PBD (plastic vs FCSEMS group; 14.2 ± 8.3 vs 12.3 ± 6.9 days, P = .426) was not significantly different between groups. Surgery-related adverse events occurred in 43.6% of the plastic stent group and 40.0% of the FCSEMS group ( P = .755). Conclusions In patients with resectable malignant biliary obstruction, the outcomes of PBD with plastic stents and FCSEMSs were similar. Considering the cost-effectiveness, PBD with plastic stents may be preferable to FCSEMS placement. (Clinical trial registration number: NCT01789502 .)
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A direct transfer of a cell sheet from a culture surface to a target tissue is introduced. Commercially available, flexible parylene is used as the culture surface, and it is proposed that the ...UV‐treated parylene offers adequate and intermediate levels of cell adhesiveness for both the stable cell attachment during culture and for the efficient cell transfer to a target surface. The versatility of this cell‐transfer process is demonstrated with various cell types, including MRC‐5, HDFn, HULEC‐5a, MC3T3‐E1, A549, C2C12 cells, and MDCK‐II cells. The novel cell‐sheet engineering is based on a mechanism of interfacial cell migration between two surfaces with different adhesion preferences. Monitoring of cytoskeletal dynamics and drug treatments during the cell‐transfer process reveals that the interfacial cell migration occurs by utilizing the existing transmembrane proteins on the cell surface to bind to the targeted surface. The re‐establishment and reversal of cell polarity after the transfer process are also identified. Its unique capabilities of 3D multilayer stacking, freeform design, and curved surface application are demonstrated. Finally, the therapeutic potential of the cell‐sheet delivery system is demonstrated by applying it to cutaneous wound healing and skin‐tissue regeneration in mice models.
The development of a transfer‐tattoo‐like cell‐sheet delivery platform is described, based on interfacial cell migration. The use of a commercially available flexible parylene film facilitates the manipulation of cell sheets and the creation of freeform designs. The efficacy of a multilayered cell‐sheet skin substitute in promoting re‐epithelialization and re‐vascularization of wounds in mouse models is demonstrated.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Obesity is a chronic low-grade inflammatory disease that is generally characterized by enhanced inflammation in obese adipose tissue (AT). Here, we investigated alterations in gene expression between ...lean and obese conditions using mRNA-Seq data derived from human purified adipocytes (ACs) and preadipocytes (preACs).
Total mRNA-seq data were generated with 27 AC and 21 preAC samples purified from human visceral AT collected during resection surgery in cancer patients, where the samples were classified into lean and obese categories by BMI > 25 kg/m
. We defined four classes of differentially expressed genes (DEGs) by comparing gene expression between (1) lean and obese ACs, (2) lean and obese preACs, (3) lean ACs and lean preACs, and 4) obese ACs and obese preACs. Based on an analysis of comparison 1, numerous canonical obesity-related genes, particularly inflammatory genes including IL-6, TNF-α and IL-1β, i.e., the genes that are expected to be upregulated in obesity conditions, were found to be expressed at significantly lower levels in obese ACs than in lean ACs. In contrast, some inflammatory genes were found to be expressed at higher levels in obese preACs than lean preACs in the analysis of comparison 2. The analysis of comparisons 3 and 4 showed that inflammatory gene classes were expressed at higher levels in differentiated ACs than undifferentiated preACs under both lean and obese conditions; however, the degree of upregulation was significantly greater for lean than for obese conditions. We validated our observations using previously published microarray transcriptome data deposited in the GEO database (GSE80654).
Taken together, our analyses suggest that inflammatory genes are expressed at lower levels in obese ACs than in lean ACs because lean adipogenesis involves even greater enhancement of inflammatory responses than does obese adipogenesis.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Piezoelectric microelectromechanical systems (PiezoMEMS) are attractive for developing next generation self-powered microsystems. PiezoMEMS promises to eliminate the costly assembly for ...microsensors/microsystems and provide various mechanisms for recharging the batteries, thereby, moving us closer towards batteryless wireless sensors systems and networks. In order to achieve practical implementation of this technology, a fully assembled energy harvester on the order of a quarter size dollar coin (diameter=24.26 mm, thickness=1.75 mm) should be able to generate about 100 μW continuous power from low frequency ambient vibrations (below 100 Hz). This paper reviews the state-of-the-art in microscale piezoelectric energy harvesting, summarizing key metrics such as power density and bandwidth of reported structures at low frequency input. This paper also describes the recent advancements in piezoelectric materials and resonator structures. Epitaxial growth and grain texturing of piezoelectric materials is being developed to achieve much higher energy conversion efficiency. For embedded medical systems, lead-free piezoelectric thin films are being developed and MEMS processes for these new classes of materials are being investigated. Non-linear resonating beams for wide bandwidth resonance are also reviewed as they would enable wide bandwidth and low frequency operation of energy harvesters. Particle/granule spray deposition techniques such as aerosol-deposition (AD) and granule spray in vacuum (GSV) are being matured to realize the meso-scale structures in a rapid manner. Another important element of an energy harvester is a power management circuit, which should maximize the net energy harvested. Towards this objective, it is essential for the power management circuit of a small-scale energy harvester to dissipate minimal power, and thus it requires special circuit design techniques and a simple maximum power point tracking scheme. Overall, the progress made by the research and industrial community has brought the energy harvesting technology closer to the practical applications in near future.
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