Bioinspired Materials:From Distinct Dimensional Architecture to Thermal Regulation Properties

The structural evolutions of the organisms during the development of billions of years endow them with remarkable thermal-regulation properties,which have significance to their survival against the outer versatile environment.Inspired by the nature,there have been extensive researches to develop thermoregulating materials by mimicking and utilizing the advantages from the natural organisms.In this review,the latest advances in thermal regulation of bioinspired microstructures are summarized,classifying the researches from dimension.The representative materials are described with emphasis on the relationship between the structural features and the corresponding thermal-regulation functions.For one-dimensional materials,wild silkworm cocoon fibers have been involved,and the reasons for unique optical phenomena have been discussed.Pyramid cone structure,grating and multilayer film structure are chosen as typical examples of two-dimensional bionics.The excellent thermal performance of the three-dimensional network frame structures is the focus.Finally,a summary and outlook are given.

Modeling Thermal Regulation in Thin Vascular Systems:A Mathematical Analysis

Mimicking vascular systems in living beings,designers have realized microvascular composites to achieve thermal regulation and other functionalities,such as electromagnetic modulation,sensing,and healing.Such material systems avail circulating fluids through embedded vasculatures to accomplish the mentioned functionalities that benefit various aerospace,military,and civilian applications.Although heat transfer is a mature field,control of thermal characteristics in synthetic microvascular systems via circulating fluids is new,and a theoretical underpinning is lacking.What will benefit designers are predictive mathematical models and an in-depth qualitative understanding of vascular-based active cooling/heating.So,the central focus of this paper is to address the remarked knowledge gap.First,we present a reduced-order model with broad applicability,allowing the inlet temperature to differ from the ambient temperature.Second,we apply mathematical analysis tools to this reduced-order model and reveal many heat transfer properties of fluid-sequestered vascular systems.We derive point-wise properties(minimum,maximum,and comparison principles)and global properties(e.g.,bounds on performance metrics such as the mean surface temperature and thermal efficiency).These newfound results deepen our understanding of active cooling/heating and propel the perfecting of thermal regulation systems.

Thermally Conductive and UV-EMI Shielding Electronic Textiles for Unrestricted and Multifaceted Health Monitoring

Skin-attachable electronics have garnered considerable research attention in health monitoring and artificial intelligence domains,whereas susceptibility to elec-tromagnetic interference(EMI),heat accumulation issues,and ultraviolet(UV)-induced aging problems pose significant constraints on their potential applications.Here,an ultra-elas-tic,highly breathable,and thermal-comfortable epidermal sensor with exceptional UV-EMI shielding performance and remarkable thermal conductivity is developed for high-fidelity monitoring of multiple human electrophysiological signals.Via filling the elastomeric microfibers with thermally conductive boron nitride nanoparticles and bridging the insulating fiber interfaces by plating Ag nanoparticles(NPs),an interwoven thermal con-ducting fiber network(0.72 W m^(-1) K^(-1))is constructed benefiting from the seamless thermal interfaces,facilitating unimpeded heat dissipation for comfort skin wearing.More excitingly,the elastomeric fiber substrates simultaneously achieve outstanding UV protection(UPF=143.1)and EMI shielding(SET>65,X-band)capabilities owing to the high electrical conductivity and surface plasmon resonance of Ag NPs.Furthermore,an electronic textile prepared by printing liquid metal on the UV-EMI shielding and thermally conductive nonwoven textile is finally utilized as an advanced epidermal sensor,which succeeds in monitoring different electrophysiological signals under vigorous electromagnetic interference.This research paves the way for developing protective and environmentally adaptive epidermal electronics for next-generation health regulation.

Tuning the phase evolution pathway of LiNi_(0.5)Mn_(1.5)O_(4) synthesis from binary intermediates to ternary intermediates with thermal regulating agent

Transition metal cation ordering is essential for controlling the electrochemical performance of cubic spinel LiNi_(0.5)Mn_(1.5)O_(4)(LNMO),which is conventionally adjusted by optimizing the high temperature sintering and annealing procedures.In this present work,multiple characterization techniques,including 6,7Li NMR,XRD and HRTEM,have been combined to trace the phase transformation and morphology evolution during synthesis.It has been illustrated that simultaneous formation of LiMn_(2)O_(4)(LMO)and LiNiO_(2)(LNO)binary oxides and their conversion into highly reactive LixNi^(3+)_(y)Mn_(3.5+)_(z)O ternary intermediate is a thermal dynamically difficult but crucial step in the synthesis of LNMO ternary oxide.A new strategy of modifying the intermediates formation pathway from binary mode to ternary mode using thermal regulating agent has been adopted.LNMO synthesized with thermal regulating agent exhibits supreme rate capability,long-cycling performance(even at elevated temperature)and excellent capacity efficiency.At a high rate of 100 C,the assembled battery delivers a discharge capacity of 99 mAh g^(-1).This study provides a way to control the formation pathway of complex oxides using thermal regulating agent.

Charging-free thermally regenerative electrochemical cycle for electricity generation from daytime solar heat and nighttime darkness

The extensive exploration of energy conversion harvested from the environment into electricity is recently driven by the significant demand to power off-grid electronics,particularly Internet-of-Things(IoT)sensors.This highlight previews the latest advance of a charging-free thermally regenerative electrochemical cycle(TREC)for continuous electricity generation from solar heat and darkness with the aid of dual-mode thermal regulations.Such a spontaneous all-day electricity generation with high power and efficiency shows great potential for powering a wide range of distributed electronics for IoT and other applications.

Ultralight and hyperelastic SiC nanofiber aerogel spring for personal thermal energy regulation

Multifunctionalization is the development direction of personal thermal energy regulation equipment in the future.However,it is still a huge challenge to effectively integrate multiple functionalities into one material.In this study,a simple thermochemical process was used to prepare a multifunctional SiC nanofiber aerogel spring(SiC NFAS),which exhibited ultralow density(9 mg/cm3),ultralow thermal conductivity(0.029 W/(m·K)at 20℃),excellent ablation and oxidation resistance,and a stable three-dimensional(3D)structure that composed of a large number of interlacing 3C-SiC nanofibers with diameters of 300–500 nm and lengths in tens to hundreds of microns.Furthermore,the as-prepared SiC NFAS displayed excellent mechanical properties,with a permanent deformation of only 1.3%at 20℃after 1000 cycles.Remarkably,the SiC NFAS exhibited robust hyperelasticity and cyclic fatigue resistance at both low(~-196℃)and high(~700℃)temperatures.Due to its exceptional thermal insulation performance,the SiC NFAS can be used for personal thermal energy regulation.The results of the study conclusively show that the SiC NFAS is a multifunctional material and has potential insulation applications in both low-and high-temperature environments.

Flexible and elastic thermal regulator for multimode intelligent temperature control

As nonlinear thermal devices,thermal regulators can intelligently respond to temperature and control heat flow through changes in heat transfer capacities,which allows them to reduce energy consumption without external intervention.However,current thermal regulators generally based on high-quality crystallinestructure transitions are intrinsically rigid,which may cause structural damage and functional failure under mechanical strain;moreover,they are difficult to integrate into emerging soft electronic platforms.In this study,we develop a flexible,elastic thermal regulator based on the reversible thermally induced deformation of a liquid crystal elastomer/liquid metal(LCE/LM)composite foam.By adjusting the crosslinking densities,the LCE foam exhibits a high actuation strain of 121%with flexibility below the nematic–isotropic phase transition temperature(TNI)and hyperelasticity above TNI.The incorporation of LMresults in a high thermal resistance switching ratio of 3.8 over a wide working temperature window of 60◦C with good cycling stability.This feature originates from the synergistic effect of fragmentation and recombination of the internal LM network and lengthening and shortening of the bond line thickness.Furthermore,we fabricate a“grid window”utilizing photic-thermal integrated thermal control,achieving a superior heat supply of 13.7℃ at a light intensity of 180mW/cm^(2)and a thermal protection of 43.4℃at 1200 mW/cm^(2).The proposed method meets the mechanical softness requirements of thermal regulatormaterials with multimode intelligent temperature control.

Environment-adaptive phase-separation-porous fluorofilm for highperformance passive radiation cooling

Passive radiative cooling is widely recognized as an environmentally sustainable method for achieving significant cooling effects.However,the mechanical properties and environmental adaptability of current radiative cooling materials are not sufficient to maintain high cooling performance in external environments.Here we reported an environment-adaptive phase-separation-porous fluorofilm for high-performance passive radiation cooling.Compared to the homogenous fluoro-porous network with limited scattering efficiencies,we modulated the porous structure of the fluorofilm to achieve a strong emissivity of 95.2%(8-13μm)and a high reflectivity of 97.1%(0.3-2.5μm).The fluorofilm demonstrates a temperature drop of 10.5°C and an average cooling power of 81 W·m^(−2)under a sunlight power of 770 W·m^(−2).The high mechanical performance and environmental adaptability of fluorofilms are also exhibited.Considering its significant radiative cooling capability and robust environmental adaptability,the fluorofilm is expected to have a promising future in radiative temperature regulation.

Evaluation of phase change materials for a light-weight building in Morocco:Effect of building’s volume,window orientation&infiltration

In this study,we will model a light-weight building made of phase change materials(PCMs)to analyze the impact of the building volume,window orientation,and air infiltration on the PCM performance.This is done by calculating the energy savings attained by the use of PCM across all of Morocco.We’ll use the commercial Rubitherm panels with RT28HC as a phase change material in this work.Typically,the EnergyPlus simulation engine is chosen to perform the modeling.The impact of building volumes is also evaluated on the PCM activation for light-weight square buildings with different side lengths of 10 m,9 m,8 m,and 7 m.Also,we looked at how well the PCM performed in terms of energy savings and thermal regulation at different window orientation placements(south,north,west,and east)and various air infiltration rates(0.5,1,1.5,and 3 ACH).This paper’s primary objective is to determine the energy savings for the PCM-enhanced building in Morocco,as well as the effect of building volume,window orientation,and infiltration on the PCM capabilities for stabilizing the indoor room temperature.The results show good indoor temperature stabilization during the summer,for the light-weight square building with a south-facing window and no air infiltration.This configuration was able to achieve a total fluctuation reduction of 1303.3℃for the 10 m building in a semi-arid environment.Besides,a high energy savings percentage of 69.56%was achieved for the PCM-enhanced building with the south-oriented window and air infiltration of 0.5 air change per hour.