Reversible Solar Heating and Radiative Cooling Devices via Mechanically Guided Assembly of 3D Macro/Microstructures.

Solar heating and radiative cooling are promising solutions for decreasing global energy consumption because these strategies use the Sun (≈5800 K) as a heating source and outer space (≈3 K) as a cooling source. Although high-performance thermal management can be achieved using these eco-friendly methods, they are limited by daily temperature fluctuations and seasonal changes because of single-mode actuation. Herein, reversible solar heating and radiative cooling devices formed via the mechanically guided assembly of 3D architectures are demonstrated. The fabricated devices exhibit the following properties: i) The devices reversibly change between solar heating and radiative cooling under uniaxial strain, called dual-mode actuation. ii) The 3D platforms in the devices can use rigid/soft materials for functional layers owing to the optimized designs. iii) The devices can be used for dual-mode thermal management on a macro/microscale. The devices use black paint-coated polyimide (PI) films as solar absorbers with multilayered films comprising thin layers of polydimethylsiloxane/silver/PI, achieving heating and cooling temperatures of 59.5 and -11.9 °C, respectively. Moreover, mode changes according to the angle of the 3D structures are demonstrated and the heating/cooling performance with skin, glass, steel, aluminum, copper, and PI substrates is investigated.

Advanced operation of heated fluidic resonators via mechanical and thermal loss reduction in vacuum.

For simultaneous and quantitative thermophysical measurements of ultrasmall liquid volumes, we have recently developed and reported heated fluidic resonators (HFRs). In this paper, we improve the precision of HFRs in a vacuum by significantly reducing the thermal loss around the sensing element. A vacuum chamber with optical, electrical, and microfluidic access is custom-built to decrease the convection loss by two orders of magnitude under 10-4 mbar conditions. As a result, the measurement sensitivities for thermal conductivity and specific heat capacity are increased by 4.1 and 1.6 times, respectively. When differentiating between deionized water (H2O) and heavy water (D2O) with similar thermophysical properties and ~10% different mass densities, the signal-to-noise ratio (property differences over standard error) for H2O and D2O is increased by 9 and 5 times for thermal conductivity and specific heat capacity, respectively.

Bidirectional thermo-regulating hydrogel composite for autonomic thermal homeostasis.

Thermal homeostasis is an essential physiological function for preserving the optimal state of complex organs within the human body. Inspired by this function, here, we introduce an autonomous thermal homeostatic hydrogel that includes infrared wave reflecting and absorbing materials for improved heat trapping at low temperatures, and a porous structure for enhanced evaporative cooling at high temperatures. Moreover, an optimized auxetic pattern was designed as a heat valve to further amplify heat release at high temperatures. This homeostatic hydrogel provides effective bidirectional thermoregulation with deviations of 5.04 °C ± 0.55 °C and 5.85 °C ± 0.46 °C from the normal body temperature of 36.5 °C, when the external temperatures are 5 °C and 50 °C, respectively. The autonomous thermoregulatory characteristics of our hydrogel may provide a simple solution to people suffering from autonomic nervous system disorders and soft robotics that are susceptible to sudden temperature fluctuations.

Boosting Thermal Conductivity by Surface Plasmon Polaritons Propagating along a Thin Ti Film.

We experimentally demonstrate boosted in-plane thermal conduction by surface plasmon polaritons (SPPs) propagating along a thin Ti film on a glass substrate. Due to the lossy nature of metal, SPPs can propagate over centimeter-scale distances even along a supported metal film, and the resulting ballistic heat conduction can be quantitatively validated. Further, for a 100-nm-thick Ti film on a glass substrate, a significant enhancement of in-plane thermal conductivity compared to bulk value (∼25%) is experimentally shown. This Letter will provide a new avenue to employ SPPs for heat dissipation along a supported thin film, which can be readily applied to mitigate hot-spot issues in microelectronics.

Modeling effective thermal conductivity enhanced by surface waves using the Boltzmann transport equation.

The thermal management of semiconductors at the device level has become a crucial issue owing to the high integration density and miniaturization of microelectronic systems. Because surface phonon polaritons (SPhPs) exhibit long propagation lengths, they are expected to contribute significantly to the heat dissipation in microelectronic systems. This study aims to numerically estimate the heat transfer due to SPhPs in a thin SiO2 film. The one-dimensional Boltzmann transport equation (BTE) is solved using the estimated propagation length based on the SPhP dispersion curves. The temperature profiles and heat fluxes are predicted and demonstrate the size effect of the film on the effective in-plane thermal conductivity of the SiO2 film. The results indicate that the temperature distribution was constant regardless of the film length and thickness because the propagation length was much longer than the film length. In addition, the heat flux increased with decreasing film thickness owing to the depth-averaged energy transfer. The effective thermal conductivities predicted using the BTE differed by ~ 16.5% from the values obtained from the analytical expression. The numerical results of this study can provide valuable data when studying the thermal behavior of SPhPs.

Nanomechanical Sensing Using Heater-Integrated Fluidic Resonators.

Micro/nanochannel resonators have been used to measure cells, suspended nanoparticles, or liquids, primarily at or near room temperature while their high temperature operation can offer promising applications such as calorimetric measurements and thermogravimetric analysis. To date, global electrothermal or local photothermal heating mechanisms have been attempted for channel resonators, but both approaches are intrinsically limited by a narrow temperature modulation range, slow heating/cooling, less quantitative heating, or time-consuming optical alignment. Here, we introduce heater-integrated fluidic resonators (HFRs) that enable fast, quantitative, alignment-free, and wide-range temperature modulation and simultaneously offer resistive thermometry and resonant densitometry. HFRs with or without a dispensing nozzle are fabricated, thoroughly characterized, and used for high throughput thermophysical properties measurements, microchannel boiling studies, and atomized spray dispensing. The HFR, without a doubt, opens a new avenue for nanoscale thermal analysis and processing and further encourages the integration of additional functions into channel resonators.

PCA-based sub-surface structure and defect analysis for germanium-on-nothing using nanoscale surface topography.

Empty space in germanium (ESG) or germanium-on-nothing (GON) are unique self-assembled germanium structures with multiscale cavities of various morphologies. Due to their simple fabrication process and high-quality crystallinity after self-assembly, they can be applied in various fields including micro-/nanoelectronics, optoelectronics, and precision sensors, to name a few. In contrast to their simple fabrication, inspection is intrinsically difficult due to buried structures. Today, ultrasonic atomic force microscopy and interferometry are some prevalent non-destructive 3-D imaging methods that are used to inspect the underlying ESG structures. However, these non-destructive characterization methods suffer from low throughput due to slow measurement speed and limited measurable thickness. To overcome these limitations, this work proposes a new methodology to construct a principal-component-analysis based database that correlates surface images with empirically determined sub-surface structures. Then, from this database, the morphology of buried sub-surface structure is determined only using surface topography. Since the acquisition rate of a single nanoscale surface micrograph is up to a few orders faster than a thorough 3-D sub-surface analysis, the proposed methodology benefits from improved throughput compared to current inspection methods. Also, an empirical destructive test essentially resolves the measurable thickness limitation. We also demonstrate the practicality of the proposed methodology by applying it to GON devices to selectively detect and quantitatively analyze surface defects. Compared to state-of-the-art deep learning-based defect detection schemes, our method is much effortlessly finetunable for specific applications. In terms of sub-surface analysis, this work proposes a fast, robust, and high-resolution methodology which could potentially replace the conventional exhaustive sub-surface inspection schemes.

Effect of Deep versus Moderate Neuromuscular Blockade on Quantitatively Assessed Postoperative Atelectasis Using Computed Tomography in Thoracic Surgery; a Randomized Double-Blind Controlled Trial.

BACKGROUND: postoperative atelectasis is a significant clinical problem during thoracic surgery with one-lung ventilation. Intraoperative deep neuromuscular blockade can improve surgical conditions, but an increased risk of residual paralysis may aggravate postoperative atelectasis. Every patient was verified to have full reversal before extubation. We compared the effect of deep versus moderate neuromuscular blockade on postoperative atelectasis quantitatively using chest computed tomography. METHODS: patients undergoing thoracic surgery were randomly allocated to two groups: moderate neuromuscular blockade during surgery (group M) and deep neuromuscular blockade during surgery (group D). The primary outcome was the proportion and the volume of postoperative atelectasis measured by chest computed tomography on postoperative day 2. The mean values of the repeatedly measured intraoperative dynamic lung compliance during surgery were also compared. RESULT: the proportion of postoperative atelectasis did not differ between the groups (1.32 [0.47-3.20]% in group M and 1.41 [0.24-3.07]% in group D, p = 0.690). The actual atelectasis volume was 38.2 (12.8-61.4) mL in group M and 31.9 (7.84-75.0) mL in group D (p = 0.954). Some factors described in the lung protective ventilation were not taken into account and might explain the atelectasis in both groups. The mean lung compliance during one-lung ventilation was higher in group D (26.6% in group D vs. 24.1% in group M, p = 0.026). CONCLUSIONS: intraoperative deep neuromuscular blockade did not affect postoperative atelectasis when compared with moderate neuromuscular blockade if full reversal was verified.

Lung sonography can improve the specificity of determination of left-sided double-lumen tracheal tube position in both novices and experts: a randomised prospective study.

OBJECTIVE: Lung sonography can be helpful to determine the position of a left-sided double-lumen tube (DLT). However, clinical experience is required for correct assessment. We investigated whether lung sonography can improve the diagnostic efficacy of determining the DLT position in novices and experts. METHODS: In this randomised prospective clinical study, 88 patients were allocated to two groups using auscultation or lung sonography for initial assessment of the DLT position. In each group, two repeated assessments were performed; the first was performed by a novice, and the second was performed by an expert. The final DLT position was confirmed by fibre-optic bronchoscopy. The primary outcome was the diagnostic efficacy (including overall accuracy, sensitivity, and specificity) in confirming the DLT position. RESULTS: In both the novices and experts, the specificity of determining the DLT position was significantly higher with lung sonography than auscultation (60.0% vs. 21.7% and 66.7% vs. 37.5%, respectively). Additionally, the predictability of an incorrect position was similar between the novices and experts using lung sonography (area under the curve of 0.665 and 0.690, respectively). CONCLUSIONS: Lung sonography can improve the diagnostic efficacy of detecting an incorrect DLT position in both novices and experts.

A Janus emitter for passive heat release from enclosures.

Passive radiative cooling functions by reflecting the solar spectrum and emitting infrared waves in broadband or selectively. However, cooling enclosed spaces that trap heat by greenhouse effect remains a challenge. We present a Janus emitter (JET) consisting of an Ag-polydimethylsiloxane layer on micropatterned quartz substrate. The induced spoof surface plasmon polariton helps overcome inherent emissivity loss of the polymer and creates near-ideal selective and broadband emission on the separate sides. This design results in not only remarkable surface cooling when the JET is attached with either side facing outwards but also space cooling when used as an enclosure wall. Thus, the JET can passively mitigate the greenhouse effect in enclosures while offering surface cooling performance comparable to conventional radiative coolers.

Dexmedetomidine Improves Locomotor Function and Alleviates Thermal Hyperalgesia Following Sciatic Nerve Crush Injury in Rats.

PURPOSE: The effects of dexmedetomidine on locomotor function and thermal hyperalgesia in sciatic nerve crush injury (SNCI) were investigated using rats. METHODS: After exposing the right sciatic nerve, the sciatic nerve was crushed for 1 minute by a surgical clip. One day after nerve injury, dexmedetomidine (5, 25, and 50 µg/kg) was directly applied to the injured sciatic nerve once a day for 14 days. Walking track analysis was used to assess locomotor function and plantar test was conducted to assess thermal pain sensitivity. Immunohistochemistry was performed to determine the expression of c-Fos in the ventrolateral periaqueductal gray (vlPAG) and paraventricular nucleus (PVN). Western blot was used to evaluate the expression level of nerve growth factor (NGF) and myelin basic protein (MBP) in the sciatic nerve. RESULTS: SNCI resulted in deterioration of locomotor function and increased thermal pain sensitivity. The level of c-Fos expression in the PVN and vlPAG was increased and the level of NGF and MBP expression in the sciatic nerve was enhanced by SNCI. Dexmedetomidine treatment improved locomotor function and upregulated expression of NGF and MBP in the sciatic nerve of SNCI. Dexmedetomidine treatment alleviated thermal hyperalgesia and downregulated expression of c-Fos in the vlPAG and PVN after SNCI. CONCLUSION: Dexmedetomidine may be used as a potential new treatment drug for recovery of locomotion and control of pain in peripheral nerve injury.

Tailoring the Spectral Absorption Coefficient of aBlended Plasmonic Nanofluid Using a CustomizedGenetic Algorithm.

Recently, plasmonic nanofluids (i.e., a suspension of plasmonic nanoparticles in a base fluid) have been widely employed in direct-absorption solar collectors because the localized surface plasmon supported by plasmonic nanoparticles can greatly improve the direct solar thermal conversion performance. Considering that the surface plasmon resonance frequency of metallic nanoparticles, such as gold, silver, and aluminum, is usually located in the ultraviolet to visible range, the absorption coefficient of a plasmonic nanofluid must be spectrally tuned for full utilization of the solar radiation in a broad spectrum. In the present study, a modern design process in the form of a genetic algorithm (GA) is applied to the tailoring of the spectral absorption coefficient of a plasmonic nanofluid. To do this, the major components of a conventional GA, such as the gene description, fitness function for the evaluation, crossover, and mutation function, are modified to be suitable for the inverse problem of tailoring the spectral absorption coefficient of a plasmonic nanofluid. By applying the customized GA, we obtained an optimal combination for a blended nanofluid with the desired spectral distribution of the absorption coefficient, specifically a uniform distribution, solar-spectrum-like distribution, and a step-function-like distribution. The resulting absorption coefficient of the designed plasmonic nanofluid is in good agreement with the prescribed spectral distribution within about 10% to 20% of error when six types of nanoparticles are blended. Finally, we also investigate how the inhomogeneous broadening effect caused by the fabrication uncertainty of the nanoparticles changes their optimal combination.

Absorption characteristics of a metal-insulator-metal nanodisk for solar thermal applications.

Due to their ability to confine light in a sub-wavelength scale and achieve coherent absorption, plasmonic nanostructures have been intensively studied for solar energy harvesting. Although nanoparticles generating localized surface plasmon resonance (LSPR) have been thoroughly studied for application in a direct absorption solar collector (DASC), nanoparticles exciting magnetic polaritons (MP) for use in a DASC have not drawn much attention. In this work, we report a metal-insulator-metal (MIM) nanodisk that can excite MP peaks apart from the LSPR in the solar spectrum. It was found that the MIM nanodisk generates a broader and relatively more uniform absorption band compared to a pure metallic nanodisk. The MP peaks were also found to cause less significant scattering compared to those associated with the LSPR. We finally showed that the peaks induced by the MIM nanodisk are highly tunable by varying the particle dimensions, making the proposed MIM nanodisk a potential candidate for solar thermal applications.

Spectrally Selective Inorganic-Based Multilayer Emitter for Daytime Radiative Cooling.

Daytime radiative coolers are used to pump excess heat from a target object into a cold exterior space without energy consumption. Radiative coolers have become attractive cooling options. In this study, a daytime radiative cooler was designed to have a selective emissive property of electromagnetic waves in the atmospheric transparency window of 8-13 µm and preserve low solar absorption for enhancing radiative cooling performance. The proposed daytime radiative cooler has a simple multilayer structure of inorganic materials, namely, Al2O3, Si3N4, and SiO2, and exhibits high emission in the 8-13 µm region. Through a particle swarm optimization method, which is based on an evolutionary algorithm, the stacking sequence and thickness of each layer were optimized to maximize emissions in the 8-13 µm region and minimize the cooling temperature. The average value of emissivity of the fabricated inorganic radiative cooler in the 8-13 µm range was 87%, and its average absorptivity in the solar spectral region (0.3-2.5 µm) was 5.2%. The fabricated inorganic radiative cooler was experimentally applied for daytime radiative cooling. The inorganic radiative cooler can reduce the temperature by up to 8.2 °C compared to the inner ambient temperature during the daytime under direct sunlight.

Removal of Hydrogen Sulfide in Septic Tanks for Treating Black Water via an Immobilized Media of Sulfur-Oxidizing Bacteria.

In South Korea, the installation of septic tanks for treating black water (STBW) is regulated even in sewage treatment areas to prevent the black water deposition in combined sewers. STBWs in which black water is anaerobically decomposed generate high concentrations of hydrogen sulfide (H2S). In this study, an immobilized media of sulfur-oxidizing bacteria (SOB) was used to remove the H2S. SOB media was prepared by using activated sludge collected from a wastewater treatment plant. Prior to field application, an appropriate cultivation period and aeration rate for SOB activation were estimated through a laboratory-scale test. The SOB was activated after a 23-day cultivation period and an aeration rate of 0.25 L-water/L-air/min. Moreover, the maximum H2S removal efficiency was observed at a cultivation period of 43 days and an aeration rate of 0.38 L-water/L-air/min. Then, the SOB media was installed on STBWs of various capacities. The H2S removal efficiency was compared between with and without SOB media. The maximum H2S elimination capacity with SOB media was 12.3 g/m3/h, which was approximately three times higher than without SOB media. Furthermore, the energy efficiency and oxidation rate were also three times higher with SOB, demonstrating the applicability of SOB for H2S removal in STBW.

Programmable Fabrication of Submicrometer Bent Pillar Structures Enabled by a Photoreconfigurable Azopolymer.

Anisotropic small structures found throughout living nature have unique functionalities as seen by Gecko lizards. Here, we present a simple yet programmable method for fabricating anisotropic, submicrometer-sized bent pillar structures using photoreconfiguration of an azopolymer. A slant irradiation of a p-polarized light on the pillar structure of an azopolymer simply results in a bent pillar structure. By combining the field-gradient effect and directionality of photofluidization, control of the bending shape and the curvature is achieved. With the bent pillar patterned surface, anisotropic wetting and directional adhesion are demonstrated. Moreover, the bent pillar structures can be transferred to other polymers, highlighting the practical importance of this method. We believe that this pragmatic method to fabricate bent pillars can be used in a reliable manner for many applications requiring the systematic variation of a bent pillar structure.

Stroke Volume Variation and Stroke Volume Index Can Predict Fluid Responsiveness after Mini-Volume Challenge Test in Patients Undergoing Laparoscopic Cholecystectomy.

Background and Objectives: For using appropriate goal-directed fluid therapy during the surgical conditions of pneumoperitoneum in the reverse Trendelenburg position, we investigated the predictability of various hemodynamic parameters for fluid responsiveness by using a mini-volume challenge test. Materials and Methods: 42 adult patients scheduled for laparoscopic cholecystectomy were enrolled. After general anesthesia was induced, CO2 pneumoperitoneum was applied and the patient was placed in the reverse Trendelenburg position. The mini-volume challenge test was carried out with crystalloid 4 mL/kg over 10 min. Hemodynamic parameters, including stroke volume variation (SVV), cardiac index (CI), stroke volume index (SVI), mean arterial pressure (MAP), and heart rate (HR), were measured before and after the mini-volume challenge test. The positive fluid responsiveness was defined as an increase in stroke volume index ≥10% after the mini-volume challenge. For statistical analysis, a Shapiro-Wilk test was used to test the normality of the data. Continuous variables were compared using an unpaired t-test or the Mann-Whitney rank-sum test. Categorical data were compared using the chi-square test. A receiver operating characteristic curve analysis was used to assess the predictability of fluid responsiveness after the mini-volume challenge. Results: 31 patients were fluid responders. Compared with the MAP and HR, the SVV, CI, and SVI showed good predictability for fluid responsiveness after the mini-volume challenge test (area under the curve was 0.900, 0.833, and 0.909, respectively; all p-values were <0.0001). Conclusions: SVV and SVI effectively predicted fluid responsiveness after the mini-volume challenge test in patients placed under pneumoperitoneum and in the reverse Trendelenburg position.

Effect of Polydeoxyribonucleotide on Lipopolysaccharide and Sevoflurane-Induced Postoperative Cognitive dysfunction in Human Neuronal SH-SY5Y Cells.

PURPOSE: Postoperative cognitive dysfunction (POCD) is a complication of surgery characterized by acute cognitive dysfunction, memory impairment, and loss of attention. The effect of polydeoxyribonucleotide (PDRN) on the POCD environment induced by lipopolysaccharide (LPS) and sevoflurane exposure were investigated in human neuronal SH-SY5Y cells. METHODS: The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and WST-8 assays were performed to determine cell viability. Cyclic adenosine-3,5'-monophosphate (cAMP), tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-6 concentrations were measured using enzyme-linked immunoassay (ELISA). Immunocytochemistry was performed for vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF), and western blotting for TNF-α, IL-1ß, IL-6, and cAMP response element-binding protein (CREB). RESULTS: Induction of the POCD environment reduced cell viability in the MTT and WST-8 assays. PDRN treatment reduced TNF-α, IL-1ß, and IL-6 expression in POCD conditions, and significantly increased cAMP concentrations and the p-CREB/CREB ratio. PDRN treatment activated adenosine A2A receptors and then increased the expression of VEGF and BDNF, which had been reduced by LPS and sevoflurane exposure. CONCLUSION: PDRN treatment showed a therapeutic effect on the LPS and sevoflurane-induced POCD environment. PDRN was shown to have an excellent therapeutic effect on POCD, not only by promoting rapid anti-inflammatory effects in damaged cells, but also by enhancing the expression of BDNF and VEGF.

Micropipette Resonator Enabling Targeted Aspiration and Mass Measurement of Single Particles and Cells.

This paper reports micropipette resonators, mechanical resonator-integrated micropipettes, which enable selective aspiration and mass measurement of particles or cells suspended in liquids with two orthogonal vibration modes. A custom pipette pulling system is built to provide power-modulated linear heating on a rotating glass capillary to make an asymmetric cross section with extended uniformity.A glass capillary is stretched with the custom puller, cut within the pulled region, polished, mounted on a machined metallic jig, and then coated with a metal. As a result, a doubly clamped tube resonator-integrated micropipette is made. For simultaneous frequency readouts of two orthogonal modes, an optical pickup, originally developed for optical data storage, is configured closely above and properly aligned to the micropipette resonator and two digital phase-locked loops are employed. For mass responsivity calibration, frequency shifts of the micropipette resonator are measured with various liquids and glass microparticles. Buoyant masses of unicellular organisms, Paramecium aurelia, freely swimming in a culture dish are successfully measured with two orthogonal modes.

Design of a Broadband Solar Thermal Absorber Using a Deep Neural Network and Experimental Demonstration of Its Performance.

In using nanostructures to design solar thermal absorbers, computational methods, such as rigorous coupled-wave analysis and the finite-difference time-domain method, are often employed to simulate light-structure interactions in the solar spectrum. However, those methods require heavy computational resources and CPU time. In this study, using a state-of-the-art modeling technique, i.e., deep learning, we demonstrate significant reduction of computational costs during the optimization processes. To minimize the number of samples obtained by actual simulation, only regulated amounts are prepared and used as a data set to train the deep neural network (DNN) model. Convergence of the constructed DNN model is carefully examined. Moreover, several analyses utilizing an evolutionary algorithm, which require a remarkable number of performance calculations, are performed using the trained DNN model. We show that deep learning effectively reduces the actual simulation counts compared to the case of a design process without a neural network model. Finally, the proposed solar thermal absorber is fabricated and its absorption performance is characterized.