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Lee SE, Seo J, Kim S, Park JH, Jin HJ, Ko J, Kim JH, Kang H, Kim JT, Lee H, Lee BJ, Kim BH. Reversible Solar Heating and Radiative Cooling Devices via Mechanically Guided Assembly of 3D Macro/Microstructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2400930. [PMID: 38940323 DOI: 10.1002/adma.202400930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 06/09/2024] [Indexed: 06/29/2024]
Abstract
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.
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Yu J, Park JY, Kim CS, Lee BJ, Seo H, Park JB, Seo YJ, Kim YK. Geriatric Nutritional Risk Index and 30-Day Postoperative Mortality in Geriatric Burn Patients. J Surg Res 2024; 301:610-617. [PMID: 39094519 DOI: 10.1016/j.jss.2024.07.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 06/19/2024] [Accepted: 07/07/2024] [Indexed: 08/04/2024]
Abstract
INTRODUCTION The geriatric nutritional risk index (GNRI) can easily identify malnutrition-associated morbidity and mortality. We investigated the association between preoperative GNRI and 30-d mortality in geriatric burn patients who underwent surgery. METHODS The study involved geriatric burn patients (aged ≥ 65 y) who underwent burn surgery between 2012 and 2022. The GNRI was computed using the following formula: 1.489 × serum albumin concentration (mg/L) + 41.7 × patient body weight/ideal body weight. Patients were dichotomized into the high GNRI (≥ 82) and low GNRI (< 82) groups. GNRI was evaluated as an independent predictor of 30-d postoperative mortality. The study also evaluated the association between GNRI and sepsis, the need for continuous renal replacement therapy (CRRT), major adverse cardiac events (MACE), and pneumonia. RESULTS Out of 270 patients, 128 (47.4%) had low GNRI (< 82). Multivariate Cox regression analysis revealed that low GNRI was significantly associated with 30-d postoperative mortality (hazard ratio: 1.874, 95% confidence interval [CI]: 1.146-3.066, P = 0.001). Kaplan-Meier analysis revealed that the 30-day mortality rate differed significantly between the low and high GNRI groups (log-rank test, P < 0.001). The 30-d postoperative mortality (hazard ratio: 2.677, 95% CI: 1.536-4.667, P < 0.001) and the incidence of sepsis (odds ratio [OR]: 2.137, 95% CI: 1.307-3.494, P = 0.004), need for CRRT (OR: 1.919, 95% CI: 1.101-3.344, P = 0.025), MACE (OR: 1.680, 95% CI: 1.018-2.773, P = 0.043), and pneumonia (OR: 1.678, 95% CI: 1.019-2.764, P = 0.044), were significantly higher in the low GNRI group than in the high GNRI group. CONCLUSIONS Preoperative low GNRI was associated with increased 30-d postoperative mortality, sepsis, need for CRRT, MACE, and pneumonia in geriatric burn patients.
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Chen Q, Choi M, Chen H, Kim J, Qin C, Ham Y, Choi M, Zeng H, Shin J, Lee BJ, Jeon S. Tree-Inspired Aerogel Comprising Nonoxidized Graphene Flakes and Cellulose as Solar Absorber for Efficient Water Generation. NANO LETTERS 2024; 24:10583-10591. [PMID: 39137020 DOI: 10.1021/acs.nanolett.4c02742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/29/2024]
Abstract
As global freshwater shortages worsen, solar steam generation (SSG) emerges as a promising, eco-friendly, and cost-effective solution for water purification. However, widespread SSG implementation requires efficient photothermal materials and solar evaporators that integrate enhanced light-to-heat conversion, rapid water transportation, and optimal thermal management. This study investigates using nonoxidized graphene flakes (NOGF) with negligible defects as photothermal materials capable of absorbing over 98% of sunlight. By combining NOGF with cellulose nanofibers (CNF) through bidirectional freeze casting, we created a vertically and radially aligned solar evaporator. The hybrid aerogel exhibited exceptional solar absorption, efficient solar-to-thermal conversion, and improved surface wettability. Inspired by tree structures, our design ensures rapid water supply while minimizing heat loss. With low NOGF content (∼10.0%), the NOGF/CNF aerogel achieves a solar steam generation rate of 2.39 kg m-2 h-1 with an energy conversion efficiency of 93.7% under 1-sun illumination, promising applications in seawater desalination and wastewater purification.
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Davey SL, Lee BJ, Robbins T, Thake CD. Prevalence of occupational heat stress across the seasons and its management amongst healthcare professionals in the UK. APPLIED ERGONOMICS 2024; 118:104281. [PMID: 38581844 DOI: 10.1016/j.apergo.2024.104281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 03/20/2024] [Accepted: 03/29/2024] [Indexed: 04/08/2024]
Abstract
Occupational heat stress (OHS) is an issue in healthcare facilities (HCFs) in the United Kingdom (UK). The aims of this study were to evaluate perceived levels of OHS during two seasons and its perceived consequences on healthcare professionals (HCPs) and to assess the efficacy of heat stress management (HSM) policies. An anonymous online survey was distributed to HCPs working in HCFs in the UK. The survey returned 1014 responses (87% women). Descriptive statistics and content analysis of survey data identified that OHS in HCFs is frequently experienced throughout the year and concerned most HCPs. Over 90% perceived OHS impairs their performance and 20% reported heat-related absenteeism. Awareness of HSM policies was poor and 73% deemed them not adequate. To help reduce the financial loss and impact on staff performance, health and well-being and patient safety, it is recommended that revisions and widespread dissemination of HSM policies are made.
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Corbett J, Young JS, Tipton MJ, Costello JT, Williams TB, Walker EF, Lee BJ, Stevens CE. Molecular biomarkers for assessing the heat-adapted phenotype: a narrative scoping review. J Physiol Sci 2023; 73:26. [PMID: 37848829 DOI: 10.1186/s12576-023-00882-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 10/03/2023] [Indexed: 10/19/2023]
Abstract
Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for individuals operating in hot environments. The efficacy of HA is typically quantified by assessing the thermo-physiological responses to a standard heat acclimation state test (i.e. physiological biomarkers), but this can be logistically challenging, time consuming, and expensive. A valid molecular biomarker of HA would enable evaluation of the heat-adapted state through the sampling and assessment of a biological medium. This narrative review examines candidate molecular biomarkers of HA, highlighting the poor sensitivity and specificity of these candidates and identifying the current lack of a single 'standout' biomarker. It concludes by considering the potential of multivariable approaches that provide information about a range of physiological systems, identifying a number of challenges that must be overcome to develop a valid molecular biomarker of the heat-adapted state, and highlighting future research opportunities.
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Ko J, Lee BJ, Lee J. Advanced operation of heated fluidic resonators via mechanical and thermal loss reduction in vacuum. MICROSYSTEMS & NANOENGINEERING 2023; 9:127. [PMID: 37829159 PMCID: PMC10564801 DOI: 10.1038/s41378-023-00575-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 06/06/2023] [Accepted: 07/04/2023] [Indexed: 10/14/2023]
Abstract
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.
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Park G, Park H, Seo J, Yang JC, Kim M, Lee BJ, Park S. Bidirectional thermo-regulating hydrogel composite for autonomic thermal homeostasis. Nat Commun 2023; 14:3049. [PMID: 37236988 DOI: 10.1038/s41467-023-38779-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 05/15/2023] [Indexed: 05/28/2023] Open
Abstract
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.
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Kim DM, Choi S, Cho J, Lim M, Lee BJ. Boosting Thermal Conductivity by Surface Plasmon Polaritons Propagating along a Thin Ti Film. PHYSICAL REVIEW LETTERS 2023; 130:176302. [PMID: 37172259 DOI: 10.1103/physrevlett.130.176302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 03/01/2023] [Indexed: 05/14/2023]
Abstract
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.
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Rue CA, D Myers S, L Coakley S, M Ashdown K, J Lee B, J Hale B, G Siddall A, C Needham-Beck S, L Hinde K, I Osofa J, S Walker F, Fieldhouse A, A J Vine C, Doherty J, R Flood T, F Walker E, Wardle S, P Greeves J, D Blacker S. Changes in physical performance during British Army Junior Entry, British Army Standard Entry and Royal Air Force Basic Training. BMJ Mil Health 2023:e002285. [PMID: 36725103 DOI: 10.1136/military-2022-002285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 12/27/2022] [Indexed: 02/03/2023]
Abstract
INTRODUCTION The purpose was to quantify physical performance in men and women during British Army Junior Entry (Army-JE), British Army Standard Entry (Army-SE) and Royal Air Force (RAF) basic training (BT). DESIGN Prospective longitudinal study. METHODS 381 participants ((339 men and 42 women) n=141 Army-JE, n=132 Army-SE, n=108 RAF) completed a 2 km run, medicine ball throw (MBT) and isometric mid-thigh pull (MTP), pre-BT and post-BT. To examine changes in pre-BT to post-BT physical test performance, for each course, paired Student t-test and Wilcoxon test were applied to normally and non-normally distributed data, respectively, with effect sizes reported as Cohen's D and with rank biserial correlations, respectively. A one-way between-subjects analysis of variance (ANOVA) (or Welch ANOVA for non-normally distributed data) compared performance between quartiles based on test performance pre-BT. Where the main tests statistic, p value and effect sizes identified likely effect of quartile, post hoc comparisons were made using Games-Howell tests with Tukey's p value. Data are presented as mean±SD, with statistical significance set at p<0.05. RESULTS During BT, 2 km run time improved by 13±46 s (-2.1%±8.1%), 30±64 s (-4.8%±12.3%) and 24±27 s (-4.5%±5.1%) for Army-JE, Army-SE and RAF, respectively (all p<0.005). MBT distance increased by 0.27±0.28 m (6.8%±7.0%) for Army-JE (p<0.001) and 0.07±0.46 m (2.3%±10.9%) for Army-SE (p=0.040), but decreased by 0.08±0.27 m (-1.4%±6.0%) for RAF (p=0.002). MTP force increased by 80±281 n (10.8%±27.6%) for Army-JE (p<0.001) and did not change for Army-SE (-36±295 n, -0.7%±20.6%, p=0.144) or RAF (-9±208 n, 1.0±17.0, p=0.603). For all tests and cohorts, participants in the lowest quartile of pre-BT performance scores demonstrated greater improvements, compared with participants in the highest quartile (except Army-JE MBT, ∆% change similar between all quartiles). CONCLUSIONS Changes in physical performance were observed for the three fitness tests following the different BT courses, and recruits with the lowest strength and aerobic fitness experienced greatest improvements.
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Ko J, Khan F, Nam Y, Lee BJ, Lee J. Nanomechanical Sensing Using Heater-Integrated Fluidic Resonators. NANO LETTERS 2022; 22:7768-7775. [PMID: 35980246 DOI: 10.1021/acs.nanolett.2c01572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
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.
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Jeong MG, Kim T, Lee BJ, Lee J. Surrogate model for optimizing annealing duration of self-assembled membrane-cavity structures. MICRO AND NANO SYSTEMS LETTERS 2022. [DOI: 10.1186/s40486-022-00148-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
AbstractWe propose a scheme to establish a surrogate model for optimizing the annealing duration of the self-assembled membrane-cavity structures from hole patterned silicon wafers. Although it has been reported that the design space of post-annealing shape can be extended by increasing the dimensions of hole arrays, the annealing duration for large hole arrays has not been well examined. A two-dimensional axisymmetric phase-field model in commercial FEM software is employed to establish the surrogate model with respect to three variables (i.e., radius, aspect ratio (AR), and normalized spacing). The established surrogate model based on the neural network indicates that the hole radius dominantly affects annealing duration and the temperature elevation (i.e., acceleration of diffusion speed) is necessary to achieve the practical annealing duration when the hole radius is larger than 1 μm.
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Jeong J, Kim T, Lee BJ, Lee J. PCA-based sub-surface structure and defect analysis for germanium-on-nothing using nanoscale surface topography. Sci Rep 2022; 12:7205. [PMID: 35504973 PMCID: PMC9065006 DOI: 10.1038/s41598-022-11185-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 04/19/2022] [Indexed: 11/09/2022] Open
Abstract
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.
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Park BM, Lee J, Jung BG, Lee BJ. Validation of the Anti-Inflammatory Effect of Tenebrio Molitor Larva Oil in a Colitis Mouse Model. Folia Biol (Praha) 2022; 68:50-58. [PMID: 36384262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Ulcerative colitis is caused by various external factors and is an inflammatory disease that causes decreased intestinal function. Tenebrio molitor larvae contain more than 30 % fat, and the fat component consists of 45 % oleic acid, 20 % linoleic acid and 20 % polyunsaturated fatty acids. In this study, after administering Tenebrio molitor larva oil (TMLO) in a dextran sodium sulphate (DSS)-induced ulcerative colitis mouse model, the pathological findings and inflammatory markers of colitis were analysed to assess whether a colitis mitigation effect was achieved. In the TMLO-administered group, the colon length increased, the spleen weight decreased, and the body weight increased compared with that in the DSS group. In addition, the disease activity index level decreased, the mRNA expression level of inflammatory cytokines in the colon decreased, and the myeloperoxidase activity level significantly decreased. Also, the activity of the NF-κB pathway involved in the regulation of the inflammatory response was lower in the TMLO group than in the DSS group. Taken together, these results suggest that TMLO suppresses occurrence of acute ulcerative colitis in the DSS mouse model. Therefore, TMLO has the potential to be developed as a health food for the prevention and treatment of ulcerative colitis.
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Lee J, Khan F, Thundat T, Lee BJ. Correction to: Microfluidic resonators with two parallel channels for independent sample loading and effective density tuning. MICRO AND NANO SYSTEMS LETTERS 2020. [DOI: 10.1186/s40486-020-00125-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
An amendment to this paper has been published and can be accessed via the original article.
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Lee J, Khan F, Thundat T, Lee BJ. Microfluidic resonators with two parallel channels for independent sample loading and effective density tuning. MICRO AND NANO SYSTEMS LETTERS 2020. [DOI: 10.1186/s40486-020-00119-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
ABSTRACTThis paper reports doubly clamped microchannel embedded resonators with two independent and parallel channels integrated for effective sample density tuning for the first time. With the aid of such a unique design, each fluidic channel can be independently accessed thus different liquid samples can be loaded simultaneously. The proposed fluidic resonators are batch fabricated by depositing silicon nitride, polysilicon, and silicon nitride sequentially on top of a set of 4-inch silicon wafers and sacrificing the middle polysilicon layer with potassium hydroxide (KOH). The sacrificial process defines two parallel channels and releases doubly clamped beam resonators simultaneously. In addition, an off-chip vacuum clamp with optical and fluidic access is custom-made to operate each resonator with enhanced quality factor. The microfluidic resonators mounted on the custom vacuum clamp are thoroughly characterized with a laser Doppler vibrometer and used to measure the effective sample density ranging from 395 to 998 kg/m3.
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Heo SY, Lee GJ, Kim DH, Kim YJ, Ishii S, Kim MS, Seok TJ, Lee BJ, Lee H, Song YM. A Janus emitter for passive heat release from enclosures. SCIENCE ADVANCES 2020; 6:6/36/eabb1906. [PMID: 32917610 PMCID: PMC7473666 DOI: 10.1126/sciadv.abb1906] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 07/24/2020] [Indexed: 05/20/2023]
Abstract
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.
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Qin C, Guo Y, Seo J, Shuai Y, Lee J, Lee BJ. Absorption characteristics of a metal-insulator-metal nanodisk for solar thermal applications. OPTICS EXPRESS 2020; 28:15731-15743. [PMID: 32403594 DOI: 10.1364/oe.393351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 05/02/2020] [Indexed: 06/11/2023]
Abstract
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.
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Chae D, Kim M, Jung PH, Son S, Seo J, Liu Y, Lee BJ, Lee H. Spectrally Selective Inorganic-Based Multilayer Emitter for Daytime Radiative Cooling. ACS APPLIED MATERIALS & INTERFACES 2020; 12:8073-8081. [PMID: 31990166 DOI: 10.1021/acsami.9b16742] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
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.
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Jo W, Choi J, Kang HS, Kim M, Baik S, Lee BJ, Pang C, Kim HT. Programmable Fabrication of Submicrometer Bent Pillar Structures Enabled by a Photoreconfigurable Azopolymer. ACS APPLIED MATERIALS & INTERFACES 2020; 12:5058-5064. [PMID: 31809014 DOI: 10.1021/acsami.9b19420] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
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.
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Ko J, Lee D, Lee BJ, Kauh SK, Lee J. Micropipette Resonator Enabling Targeted Aspiration and Mass Measurement of Single Particles and Cells. ACS Sens 2019; 4:3275-3282. [PMID: 31762257 DOI: 10.1021/acssensors.9b01843] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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.
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Seo J, Jung PH, Kim M, Yang S, Lee I, Lee J, Lee H, Lee BJ. Design of a Broadband Solar Thermal Absorber Using a Deep Neural Network and Experimental Demonstration of Its Performance. Sci Rep 2019; 9:15028. [PMID: 31636300 PMCID: PMC6803693 DOI: 10.1038/s41598-019-51407-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 09/24/2019] [Indexed: 11/29/2022] Open
Abstract
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.
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Kim T, Kim DM, Lee BJ, Lee J. Soft and Deformable Sensors Based on Liquid Metals. SENSORS 2019; 19:s19194250. [PMID: 31574955 PMCID: PMC6806167 DOI: 10.3390/s19194250] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 09/24/2019] [Accepted: 09/27/2019] [Indexed: 12/14/2022]
Abstract
Liquid metals are one of the most interesting and promising materials due to their electrical, fluidic, and thermophysical properties. With the aid of their exceptional deformable natures, liquid metals are now considered to be electrically conductive materials for sensors and actuators, major constituent transducers in soft robotics, that can experience and withstand significant levels of mechanical deformation. For the upcoming era of wearable electronics and soft robotics, we would like to offer an up-to-date overview of liquid metal-based soft (thus significantly deformable) sensors mainly but not limited to researchers in relevant fields. This paper will thoroughly highlight and critically review recent literature on design, fabrication, characterization, and application of liquid metal devices and suggest scientific and engineering routes towards liquid metal sensing devices of tomorrow.
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Lee BJ, Lee J. Beyond mass measurement for single microparticles via bimodal operation of microchannel resonators. MICRO AND NANO SYSTEMS LETTERS 2019. [DOI: 10.1186/s40486-019-0088-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Choi WR, Lee BJ, Kim JH. Long-term outcome following resection of sinonasal inverted papillomas: A single surgeon's experience in 127 patients. Clin Otolaryngol 2019; 44:652-655. [PMID: 30854775 DOI: 10.1111/coa.13325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Revised: 02/02/2019] [Accepted: 02/15/2019] [Indexed: 11/29/2022]
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Jo YH, Choi WM, Kim DG, Zargaran A, Sohn SS, Kim HS, Lee BJ, Kim NJ, Lee S. FCC to BCC transformation-induced plasticity based on thermodynamic phase stability in novel V 10Cr 10Fe 45Co xNi 35-x medium-entropy alloys. Sci Rep 2019; 9:2948. [PMID: 30814569 PMCID: PMC6393512 DOI: 10.1038/s41598-019-39570-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Accepted: 01/21/2019] [Indexed: 11/09/2022] Open
Abstract
We introduce a novel transformation-induced plasticity mechanism, i.e., a martensitic transformation from fcc phase to bcc phase, in medium-entropy alloys (MEAs). A VCrFeCoNi MEA system is designed by thermodynamic calculations in consideration of phase stability between bcc and fcc phases. The resultantly formed bcc martensite favorably contributes to the transformation-induced plasticity, thereby leading to a significant enhancement in both strength and ductility as well as strain hardening. We reveal the microstructural evolutions according to the Co-Ni balance and their contributions to a mechanical response. The Co-Ni balance plays a leading role in phase stability and consequently tunes the cryogenic-temperature strength-ductility balance. The main difference from recently-reported metastable high-entropy dual-phase alloys is the formation of bcc martensite as a daughter phase, which shows significant effects on strain hardening. The hcp phase in the present MEA mostly acts as a nucleation site for the bcc martensite. Our findings demonstrate that the fcc to bcc transformation can be an attractive route to a new MEA design strategy for improving cryogenic strength-ductility.
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