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The development of smart stents that can monitor cardiovascular diseases and communicate vascular abnormalities to medical doctors has received significant attention in the field of biomedical engineering. Various in-situ fabrication strategies have been proposed to simultaneously fabricate the smart stent and pressure sensor, reducing the risk of sensor detachment due to the flow of blood. However, the rigidity of the wireless pressure sensor still limit the practical utility of these devices. In this study, we propose a flexible and stretchable wireless pressure sensor-integrated smart self-reporting stent. The fabrication process has been optimized to produce a serpentine-shaped wireless pressure sensor that matches the shape and flexibility of the polymer stent strut. This approach minimizes the interfacial effect between the wireless pressure sensor and the stent strut, ensuring the accuracy and reliability of the information provided by the smart stent. We thoroughly investigated the structural integrity, resonance frequency, stretchability, flexibility and radial force of the fabricated smart self-reporting stent under different conditions. The device demonstrated exceptional sensitivity, as low as 0.15 MHz/mmHg. The feasibility of the proposed smart stent is demonstrated by implantation into the arteries of a three-dimensional (3D) phantom. The obtained results and the flexible and stretchable nature of the proposed smart self-reporting stent demonstrate its potential to be effective, and durable for monitoring the functional dynamics of the heart and detecting in-stent restenosis.

To date, several smart stents have been proposed to continuously detect biological cues, which is essential for tracking patients' critical vital signs and therapy. However, the proposed smart stent fabrication techniques rely on conventional laser micro-cutting or 3D printing technologies. The sensors are then integrated into the stent structure using an adhesive, conductive epoxy, or laser micro-welding process. The sensor packaging method using additional fabrication processes can cause electrical noise, and there is a possibility of sensor detachment from the sent structure after implantation, which may pose a significant risk to patients. Herein, we are demonstrating for the first time a single-step fabrication method to develop a smart stent with an integrated sensor for detecting in-stent restenosis and assessing the functional dynamics of the heart. The smart stent is fabricated using a microelectromechanical system (MEMS)-based micromachining technology. The proposed smart stent can detect biological cues without additional power and wirelessly transmit the signal to the network analyzer. The cytocompatibility of the smart stent is confirmed through a cytotoxicity test by monitoring the cell growth, proliferation, and viability of the cultured cardiomyocytes. The capacitance of the smart stent exhibits an excellent linear relationship with the applied pressure. The exceptional sensitivity of the pressure sensor enabled the proposed smart stent to detect biological cues during

This paper proposes the use of sensor-integrated silicon cantilever arrays to measure drug-induced cardiac toxicity in real time. The proposed cantilever sensors, unlike the conventional electrophysiological methods, aim to evaluate cardiac toxicity by measuring the contraction force of the cardiomyocytes corresponding to the target drugs. The surface of the silicon cantilever consists of microgrooves to maximize the alignment and the contraction force of the cardiomyocytes. This type of surface pattern also helps in the maturation of the cardiomyocytes by increasing the sarcomere length. The preliminary characterization of the cantilever sensors was performed on the cantilever surface, with the cardiomyocytes seeded with a density of 1000 cells/mm2, and the cardiac contractility was measured as a function of the culture days. The change in the contraction force of the cardiomyocytes due to the drug concentration was successfully measured through the integrated strain sensor in the culture media. The reliability of the sensor-integrated cantilevers and the feasibility of their mass production ensure that they meet the practical requirements in the medical applications.

This study presents the dynamic modeling of preferential CO oxidation (CO-PROX) over a Pt–Fe/γ-Al2O3 catalyst in a monolithic reactor under both adiabatic and isothermal conditions. The modeling allowed us to investigate the effects of disturbance of the inlet conditions on transient performance. This work includes a mathematical description of the heat- and mass-transfer of species with a quasi-2D approach and a global kinetic mechanism. The model was validated by simulating the steady-state operation of the CO-PROX isothermal reactor and comparison of the predictions with experimental data obtained between 363 and 553 K at atmospheric pressure. The CO-PROX reactor model proved to be robust and accurate in the high-temperature regime (>410 K) and can be used for real-time simulation. The high response sensitivity of the adiabatic reactor predicted a significant improvement in CO conversion at temperatures from 435 K with the addition of a small amount of energy while maintaining a response time of 15 s. The isothermal reactor exhibited a reasonably fast response time when exposed to a realistic gas hourly space velocity scheme based on transient fuel demand in a proton exchange membrane fuel cell system.

Recently, transition-metal-based hydroxide materials have attracted significant attention in various electrochemical applications owing to their low cost, high stability, and versatility in composition and morphology. Among these applications, transition-metal-based hydroxides have exhibited significant potential in supercapacitors owing to their multiple redox states that can considerably enhance the supercapacitance performance. In this study, nanostructured Ni-Mn double hydroxide is directly grown on a conductive substrate using an electrodeposition method. Ni-Mn double hydroxide exhibits excellent electrochemical charge-storage properties in a 1 M KOH electrolyte, such as a specific capacitance of 1364 Fg-1 at a current density of 1 mAcm-2 and a capacitance retention of 94% over 3000 charge-discharge cycles at a current density of 10 mAcm-2. The present work demonstrates a scalable, time-saving, and cost-effective approach for the preparation of Ni-Mn double hydroxide with potential application in high-charge-storage kinetics, which can also be extended for other transition-metal-based double hydroxides.

The engineered photoelectrodes have received significant attention in the photoelectrochemical (PEC) applications. Herein, we prepared a highly effective photoelectrode based on Cu2O decorated with ZnO and rGO for efficient PEC water splitting. Firstly, different thickness Cu2O is sputtered on the FTO substrate (FC). The PEC performance of the FC photoelectrode further improved by depositing the ZnO and rGO protection layers (FCZG). The fabricated photoelectrodes are systematically investigated for their morphological and crystal structure by AFM, FESEM, TEM, XPS, XRD, and RAMAN, UVDRS, and PL analysis. The FCZG hybrid photoelectrode exhibit a photocurrent density of 4.94 mA cm−2 at 0 V vs. reversible hydrogen electrode (RHE), which is 1.5 times higher than the unmodified photoelectrodes. The improved PEC performance of the FCZG hybrid photoelectrode is due to the high surface roughness, larger electrochemical active surface area, and less radiative recombination rate of the photogenerated charge carriers.

This study aims to analyze effect of needle position inside nozzle on the internal and external flow characteristics. To visualize cavitating flow inside nozzle, the transparent acrylic nozzle was used. We tested five needle positions that simulated the needle movement of injector. The cross-section of test nozzle is rectangular with a very narrow width instead of circular shaped for a better visualization of cavitating flow. The inside of the nozzle was visualized by the shadowgraphic visualization using a high-speed camera and a metal-halide lamp. From the experiments, development of the cavitating flow according to the needle positions depends on the flow velocity and the cavitation number. The cavitation length, cavitation width, and spray angle are relatively symmetrically shown when the needle was at the center. However, they were asymmetrical when the needle position was biased. When the needle positions were in the same on the vertical line, the minimum cavitation length, minimum cavitation width, and minimum spray angle were larger when the upper level. The needle position affects the development timing and cavitation growth. When the needle position was located at the upper level, the hydraulic flip occurred at a higher injection pressure than the lower level.

The vertically aligned one-dimensional (1D) core–shell structure can maximize the exposure and use of the functionally active surface while maintaining the geometric effects caused by the underlying structure. Herein, we have fabricated 1D vertically aligned ZnO/V2O5 core–shell hetero-nanostructure nanorod arrays (NRs) for photoelectrochemical (PEC) water splitting. ZnO/V2O5 NRs were prepared through the hydrothermal growing of ZnO NRs and then radio frequency (RF) magnetron sputtering deposition of V2O5 for 300, 600 and 900 s. The photocurrent density of ZnO/V2O5-based photoanodes was gradually increased with the sputtering time, reaching the maximum value of 1.21 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) for ZnO/V2O5-600, whereas for pure ZnO-based photoanode was 0.42 mA/cm2. The incident photon to electron conversion efficiency (IPCE) of ZnO/V2O5-600 evaluated to be 82.3% which was 2.3 times higher than that of ZnO (36.4%). The improved PEC performance of ZnO/V2O5-600 is because the core–shell structure with a moderate thickness of the V2O5 layer has the extremely high carrier density, largest electrochemically active surface area (ECSA), largest carrier density, lowest charge recombination rate, and the longest lifetime of e-h pairs due to the formation of the staggered gap junction. This study provides an effective way to design and fabrication of hetero-nanostructures for high-efficiency photoelectrodes.

MnCo2S4/CoS2 electrode with highly accessible electroactive sites is prepared using the hydrothermal method. The electrode exhibits an areal capacitance of 0.75 Fcm-2 at 6 mAcm-2 in 1 M KOH. The capacitance is further increased to 2.06 Fcm-2 by adding K3Fe(CN)6 and K4Fe(CN)6 (a redox couple) to KOH. This increment is associated with the redox-active properties of cobalt and manganese transition metals, as well as the ion pair of [Fe(CN)6]-3/[Fe(CN)6]-4. The capacitance retention of the MnCo2S4/CoS2 electrode is 87.5% for successive 4000 charge-discharge cycles at 10 mAcm-2 in a composite electrolyte system of KOH and ferri/ferrocyanide. The capacitance enhancement is supported by the lowest equivalent series resistance (0.62 Ωcm-2) of MnCo2S4/CoS2 in the presence of redox additive couple compared with the bare KOH electrolyte.

Vanadium sulfide (VS2) nanomaterials have been deposited on surface-modified stainless steel mesh (SMSSM) by facial hydrothermal method and subsequent effects of acidic etching on surface morphology and supercapacitive performance of the electrode were studied. The acid etching process improves the coupling interaction between the stainless steel mesh and active materials. The optimized 1% etched SMSSM with VS2 (1%/VS2) loaded electrode reveals the porous fine nanoparticles composed surface nanostructure. The prepared 1%/VS2 electrode exhibited an excellent areal capacitance of 45.83 mF/cm2, which is two times higher than that of a non-etched VS2 loaded electrode. These results showed that the acidic etching process significantly improved the surface nanostructure of the VS2 material that improved the capacitance of the SMSSM substrate.

Manganese sulfide usually exists as MnS2 (cubic), β-MnS (zinc blende), γ-MnS (wurtzite), and α-MnS (rock salt) polymorphs. In this study, polymorphic thin films of MnS2, γ-MnS, and α-MnS were prepared from manganese carbonate through anion exchange and controlled reaction kinetics via a hydrothermal method. At the same mass ratio (1 : 1) of manganese carbonate to the S precursor, the hydrothermal anion-exchange kinetics were used to determine the phases (MnS2, γ-MnS, and α-MnS) of manganese sulfide. The α-MnS phase was obtained at a high S precursor content, specifically at a mass ratio of 1 : 5, even at 363 K. The different prepared phases (MnS2, γ-MnS, and α-MnS) exhibited superior O2 evolution reaction activities (overpotential: 301, 342, and 292 mV, respectively) compared with pristine manganese carbonate (overpotential: 480 mV) in a 1 M KOH electrolyte to drive a current density of 10 mA cm−2. Among all the polymorphs, α-MnS exhibited the lowest overpotential because it had the lowest charge-transfer resistance (8.9 Ω cm−2), edge sharing MnS6 octahedra with more active sites and highest electrochemical active surface area (360 cm−2). This study provides a new approach to control the phase of transition-metal chalcogenides for improved electrochemical reactions.

In this paper, we propose a flexible wire-type hybrid supercapacitor (FWHSC) endowed with superior electrochemical properties of transition metal sulfide nano-flakes. The electrodeposition method was conducted for coating of electroactive transition metal sulfide (CoS, NiCo2S4, CoS/NiCo2S4 and ZnCo2S4) nanomaterials on the current collector (Cu-wire), which makes it possible to store the electrochemical energy. The electrochemical study of NiCo2S4 and ZnCo2S4 electrodes revealed excellent charge storage features with areal capacitance of 245.5 and 104.6 mF cm−2, respectively, at a scan rate of 2 mV s−1. The FWHSC assembled from Cu@CoS/NiCo2S4 and Cu@ZnCo2S4 electrodes and KOH/PVA gel electrolyte operates in a voltage range of 1.5 V and delivers a specific energy of 6 W h kg−1 at the specific power of 4500 W kg−1 and a cycling stability of over 2000 cycles.

Studies related to low temperature and their effect on cardiomyocytes are essential as hypothermia—like situations have been known to induce arrhythmia or ventricular fibrillation. Till date, several studies have been carried out on animals and their electrophysiological responses have been studied in the form of action potential. However, for a complete assessment of the effect of low temperature, mechanophysiological changes along with electrophysiological changes need to be investigated, at the tissue level. In this study, the effect of culture temperature on cell growth has been studied by measuring the field potential and contractility of human induced pluripotent stem cell-derived cardiomyocytes. This study has the potential to further improve the understanding of low temperature on human cells.

In this study, we developed a multi-layered functional cantilever for real-time force measurement of cardiomyocytes in cell culture media. The functional cantilever with a full-bridge circuit configuration was composed of one polydimethylsiloxane (PDMS) and two polyimide (PI) layers, forming two resistive sensors on each upper side of the two PI layers. The PI layers were chemically bonded using an oxygen plasma treatment, with a thin composite layer consisting of Cr/SiO2/PDMS. These greatly improved the force sensitivity and the long-term reliability of the integrated strain sensor operating in liquids. The nanogrooved PDMS top layer bonded on the upper PI layer was employed to further improve the growth of cardiomyocytes on the functional cantilever. The difference in resistance changes and response characteristics was confirmed by evaluating the characteristics of the multi-layered polymer cantilevers with half-bridge and full-bridge circuit configurations. We also employed the cantilever devices to measure the contraction force of cardiomyocytes for 16 days and side effects in real time in human-induced pluripotent stem cells treated with the cardiovascular drug verapamil. The sensor-integrated cantilever devices are expected to be utilized as a novel biomedical sensor for evaluating the mechanobiology of cardiomyocytes, as well as in drug screening tests.

Herein, we propose an array of gold (Au)-coated SU-8 cantilevers with microgrooves for improved maturation of cardiomyocytes and describe its applications to drug-induced cardiac toxicity tests. Firstly, we evaluated the effect of cell culture substrates such as polydimethylsiloxane (PDMS), polyimide (PI), and SU-8 on the cardiomyocyte's maturation. Among these, the SU-8 with microgroove structures exhibits improved cardiomyocyte maturation. Further, thin layers of graphene and Au are coated on SU-8 substrates and the effects of these materials on cardiomyocyte maturation are evaluated by analyzing the expression of proteins such as alpha-actinin, Connexin 43 (Cx43), and Vinculin. While both conductive materials enhanced protein expression when compared to bare SU-8, the Au-coated SU-8 substrates demonstrated superior cardiomyocyte maturation. The cantilever structure is constructed using microgroove patterned SU-8 with and without an Au coating. The Au-coated SU-8 cantilever showed maximum displacement of 17.6 ± 0.3 μm on day 21 compared to bare SU-8 (14.2 ± 0.4 μm) owing to improved cardiomyocytes maturation. Verapamil and quinidine are used to characterize drug-induced changes in the contraction characteristics of cardiomyocytes on bare and Au-coated SU-8 cantilevers. The relative contraction forces and beat rates changed according to the calcium and sodium channel related drugs. Matured cardiomyocytes are less influenced by the drugs compared to immature cardiomyocytes and showed reliable IC50 values. These results indicate that the proposed Au-coated SU-8 cantilever array could help improve the accuracy of toxicity screening results by allowing for the use of cardiomyocytes that have been matured on the drug screening platform.

Background: We have designed a reinforced drug-loaded vascular graft composed of polycaprolactone (PCL) and polydioxanone (PDO) via a combination of electrospinning/3D printing approaches. To evaluate its potential for clinical application, we compared the in vivo blood compatibility and performance of PCL/PDO + 10%DY grafts doped with an antithrombotic drug (dipyridamole) with a commercial expanded polytetrafluoroethylene (e-PTFE) graft in a porcine model. Methods: A total of 10 pigs (weight: 25–35 kg) were used in this study. We made a new 5-mm graft with PCL/PDO composite nanofiber via the electrospinning technique. We simultaneously implanted a commercially available e-PTFE graft (n = 5) and our PCL/PDO + 10%DY graft (n = 5) into the carotid arteries of the pigs. No anticoagulant/antiplatelet agent was administered during the follow-up period, and ultrasonography was performed weekly to confirm the patency of the two grafts in vivo. Four weeks later, we explanted and compared the performance of the two grafts by histological analysis and scanning electron microscopy (SEM). Results: No complications, such as sweating on the graft or significant bleeding from the needle hole site, were seen in the PCL/PDO + 10%DY graft immediately after implantation. Serial ultrasonographic examination and immunohistochemical analysis demonstrated that PCL/PDO + 10%DY grafts showed normal physiological blood flow and minimal lumen reduction, and pulsed synchronously with the native artery at 4 weeks after implantation. However, all e-PTFE grafts occluded within the study period. The luminal surface of the PCL/PDO + 10%DY graft in the transitional zone was fully covered with endothelial cells as observed by SEM. Conclusion: The PCL/PDO + 10%DY graft was well tolerated, and no adverse tissue reaction was observed in porcine carotid models during the short-term follow-up. Colonization of the graft by host endothelial and smooth muscle cells coupled with substantial extracellular matrix production marked the regenerative capability. Thus, this material may be an ideal substitute for vascular reconstruction and bypass surgeries. Long-term observations will be necessary to determine the anti-thrombotic and remodeling potential of this device.

Drug-induced cardiotoxicity is a potentially severe side effect that can alter the contractility and electrophysiology of the cardiomyocytes. Cardiotoxicity is generally assessed through animal models using conventional drug screening platforms. Despite significant developments in drug screening platforms, the difficulty in measuring electrophysiology and contractile profile together affects the investigation of cardiotoxicity in potential drugs. Some drugs can prove to be more toxic to contractility than electrophysiology, which demands the need for a reliable, dual, and simultaneous drug screening platform. Herein, we propose the microelectrode array integrated SU-8 cantilever for dual and simultaneous measurement of electrophysiology and contractility of cardiomyocytes. The SU-8 cantilever is integrated with microelectrode array (C-MEA) using conventional photolithographic techniques. Drug tests are conducted to verify the feasibility of the C-MEA platform using three cardiovascular drugs. Clinically recognized drugs, quinidine and verapamil, are used to activate both the hERG channel and the contractile characteristics of cardiomyocytes. The effect of ion channel blockers on the field potential duration (FPD) of the cardiomyocytes is compared with several contractility-based parameters. The contraction-relaxation duration (CRD) profile is relatively close to that of FPD in tested drugs (half-maximal (IC

Herein, we proposed a SU-8 based wireless pressure sensor integrated with a polycaprolactone (PCL) based bioresorbable scaffold (BRS) for the detection of biological cues. The PCL-based BRS and pressure sensor are fabricated using a custom-designed additive manufacturing method and a modified photolithography technique. Firstly, we optimized the additive manufacturing fabrication parameters to realize the highly reliable scaffold with uniform strut width and thickness. Then, utilizing the optimized additive manufacturing conditions, we fabricated three distinct types of scaffolds, namely scaffold A, scaffold B, and scaffold C, each with a unique architecture. The preliminary characteristics of the fabricated scaffolds demonstrated that the scaffold A architecture exhibited superior properties, including 0.048 N mm−1 radial force, 1.64% foreshortening, and 14.1% recoil compared to the scaffolds B and C. The Inductor-Capacitor (LC)-pressure sensor is integrated into the PCL-based BRS using a water-soluble polyvinyl alcohol adhesive layer. The reliability of the fabricated LC-pressure sensor is confirmed by measuring its change capacitance and resonance frequency at different applied pressures. The proposed LC-pressure sensor integrated PCL-based BRS is evaluated in a pressure range of 0–280 mmHg. The resonant frequency of the fabricated smart scaffold changed linearly according to the pressure change indicating the high reliability of the proposed smart scaffold. We anticipate that the proposed pressure sensor integrated with the biodegradable PCL-based BRS would be used for biomedical applications owing to their facile fabrication process and excellent sensitivity.

Surface topography of devices is crucial for cardiac tissue engineering. In this study, we fabricated a unique cantilever-based device, whose surface was structured with stress-assisted micro-wrinkles. The Au micro-wrinkle patterns on the cantilever surface helped the cardiomyocytes to grow similarly to those in the native cardiac tissues by aligning them and providing them a conductive surface, thereby enhancing the contractile properties of the cells. The patterned Au surface also enhanced the electrical conductivity during cell-to-cell interactions. Additionally, the expression levels of proteins related to intracellular adhesion and contraction significantly increased in the polymer cantilevers with metallic wrinkle patterns. The roles of the polymer cantilever in improving the electrical conductivity and force-sensing properties were confirmed. Thereafter, the cantilever's response to cardiotoxicity was evaluated by introducing drugs known to induce toxicity to cardiomyocytes. The proposed cantilever is a versatile device that may be used to screen drug-induced cardiotoxicity during drug development.