Pediatric vehicular hyperthermia (PVH) has aroused wide public concern recently. High temperatures in closed vehicles with full sun exposure and no ventilation in summer seriously endanger children's lives. Aiming at this practical problem, this study first took the temperature of child's core body as a standard, and divided the hyperthermia into three stages: un-compensable heating (Tc > 37ºC), heat stroke (Tc > 40ºC) and critical thermal maximum (Tc > 42ºC). On this basis, two weeks of outdoor parking experiments during 10:00-18:00, using an equivalent size dummy were conducted to explore the influence of ambient temperature and solar irradiation on cabin temperature, humidity, and child's core body temperature. According to the experimental results, at an ambient temperature of 32.4ºC, the child in the cabin developed un-compensable heating within 72â¯min, suffered heat stroke within 129â¯min, and reached the critical thermal maximum within 151â¯min. Considering the limitations of the experiment, a numerical study was conducted to analyze the effects of ambient temperature, solar irradiation, and window radiation characteristics on cabin temperature and flow fields comprehensively. Simulation results were in good agreement with the experiments: even at low ambient temperature Ta = 23ºC or weak solar irradiation (ts = 18:00) condition, the temperature in a closed compartment could reach the "hazardous" level. This study can provide guidance for public to increase security and prevention awareness, and promote the development of relevant policies and technologies.
Temperature , Humans , Body Temperature , Child , Humidity , Hot Temperature , Hyperthermia , Heat Stroke , Automobiles , Sunlight
The active-cooling elastomer concept, originating from vascular thermoregulation for soft biological tissue, is expected to develop an effective heat dissipation method for human skin, flexible electronics, and soft robots due to the desired interface mechanical compliance. However, its low thermal conduction and poor adaptation limit its cooling effects. Inspired by the bone structure, this work reports a simple yet versatile method of fabricating arbitrary-geometry liquid metal skeleton-based elastomer with bicontinuous Gyroid-shaped phases, exhibiting high thermal conductivity (up to 27.1 W/mK) and stretchability (strain limit >600%). Enlightened by the vasodilation principle for blood flow regulation, we also establish a hydraulic-driven conformal morphing strategy for better thermoregulation by modulating the hydraulic pressure of channels to adapt the complicated shape with large surface roughness (even a concave body). The liquid metal active-cooling elastomer, integrated with the flexible thermoelectric device, is demonstrated with various applications in the soft gripper, thermal-energy harvesting, and head thermoregulation.
Cryopreservation can keep the bioactivity of biological specimens in long-term storage, but it is hard to retain the structural integrity due to serious thermomechanical stress during cooling and warming procedures, especially for complex living organisms. Few studies have reported on the thermomechanical stress of biological specimens in a pre-freezing supercooled state, which is a widespread phenomenon in slow-rate freezing cryopreservation. Here, we develop a thermomechanical coupling model to study transient thermal and mechanical fields of supercooled biological specimens experiencing freezing procedures. The results show that cryoprotectant accumulation in insects causes pronounced supercooled phenomena with severe deformation and thermomechanical stress in the initial state of phase transition. However, the loss of freezable water induced that final deformation and stress decrease, which is beneficial to organism survival after freezing. This numerical method is proved to be a guideline for optimizing slow-rate freezing cryopreservation protocols efficiently and economically. These results reveal survival mechanisms of insects with supercooled phenomena after freezing and assist researchers in exploring more valuable cryopreservation methods for biological specimens.
Cryopreservation , Insecta , Animals , Cold Temperature , Phase Transition , Water
The hazards caused by drug-resistant bacteria are rocketing along with the indiscriminate use of antibiotics. The development of new non-antibiotic antibacterial drugs is urgent. The excellent biocompatibility and diverse multifunctionalities of liquid metal have stimulated the studies of antibacterial application. Several gallium-based antimicrobial agents have been developed based on the mechanism that gallium (a type of liquid metal) ions disorder the normal metabolism of iron ions. Other emerging strategies, such as physical sterilization by directly using LM microparticles to destroy the biofilm of bacteria or thermal destruction via infrared laser irradiation, are gaining increasing attention. Different from traditional antibacterial agents of gallium compounds, the pronounced property of gallium-based liquid metal materials would bring innovation to the antibacterial field. Here, LM-based antimicrobial mechanisms, including iron metabolism disorder, production of reactive oxygen species, thermal injury, and mechanical destruction, are highlighted. Antimicrobial applications of LM-based materials are summarized and divided into five categories, including liquid metal motors, antibacterial fabrics, magnetic field-responsive microparticles, liquid metal films, and liquid metal polymer composites. In addition, future opportunities and challenges towards the development and application of LM-based antimicrobial materials are presented.
Phase change materials have attracted significant attention due to their promising applications in many fields like solar energy and chip cooling. However, they suffer leakage during the phase transition process and have relatively low thermal conductivity. Here, through introducing hard magnetic particles, we synthesize a kind of magnetically tightened form-stable phase change materials. They achieve multifunctions such as leakage-proof, dynamic assembly, and morphological reconfiguration, presenting superior high thermal (increasing of 1400-1600%) and electrical (>104 S/m) conductivity, and prominent compressive strength, respectively. Furthermore, free-standing temperature control and high-performance thermal and electric conversion systems based on these materials are developed. This work suggests an efficient way toward exploiting a smart phase change material for thermal management of electronics and low-grade waste heat utilization.
The excellent stretchability and biocompatibility of flexible sensors have inspired an emerging field of plant wearables, which enable intimate contact with the plants to continuously monitor the growth status and localized microclimate in real-time. Plant flexible wearables provide a promising platform for the development of plant phenotype and the construction of intelligent agriculture via monitoring and regulating the critical physiological parameters and microclimate of plants. Here, the emerging applications of plant flexible wearables together with their pros and cons from four aspects, including physiological indicators, surrounding environment, crop quality, and active control of growth, are highlighted. Self-powered energy supply systems and signal transmission mechanisms are also elucidated. Furthermore, the future opportunities and challenges of plant wearables are discussed in detail.
Wearable Electronic Devices , Agriculture , Monitoring, Physiologic , Plants
Shape transformable materials that can respond to external environments have attracted widespread interest over the fields of soft robotics, flexible electronics, and tissue engineering. Among stimuli-responsive materials, liquid metals exhibit rather unique characteristics of versatile morphological changes upon diverse stimuli, including chemicals, electrical field, and mechanical force, etc. Herein, a superfast (few milliseconds), large-scaled (13.8% deformation increase), and fierce (cracks formation) transformation of liquid metal microdroplets (LMMs) with strong impulse expanded force due to liquid-solid phase transition in a dual fluid system composed of LMMs and aqueous solution is reported. When subject to low-temperature stimulus, LMM would transform from ellipsoidal shape to amorphous shape induced by thermal stress, driving the shape morphing. Furthermore, the phase changes of LMMs as well as the formation of surrounding ice crystals are proven to be responsible for this phenomenal behavior. The densification of ice crystals is demonstrated to play a significant role in the transformable behavior. In particular, these nonconductive LMMs in aqueous solutions are discovered to turn into conducive materials with an impedance change of about 105 times. The present discovery is of fundamental and practical significance, and would open new venues in fields such as fluid mechanics, thermal science, flexible electronics, biomedicine, and so forth.
It is remarkably desirable and challenging to design a stretchable conductive material with tunable electromagnetic-interference (EMI) shielding and heat transfer for applications in flexible electronics. However, the existing materials sustained a severe attenuation of performances when largely stretched. Here, a super-stretchable (800% strain) liquid metal foamed elastomer composite (LMF-EC) is reported, achieving super-high electrical (≈104 S cm-1) and thermal (17.6 W mK-1) conductivities under a large strain of 400%, which also exhibits unexpected stretching-enhanced EMI shielding effectiveness of 85 dB due to the conductive network elongation and reorientation. By varying the liquid and solid states of LMF, the stretching can enable a multifunctional reversible switch that simultaneously regulates the thermal, electrical, and electromagnetic wave transport. Novel flexible temperature control and a thermoelectric system based on LMF-EC is furthermore developed. This work is a significant step toward the development of smart electromagnetic and thermal regulator for stretchable electronics.
It is remarkably desirable and challenging to design reconfigurable ferromagnetic materials with high electrical conductivity. This has attracted great attention due to promising applications in many fields such as emerging flexible electronics and soft robotics. However, the shape and magnetic polarity of existing ferromagnetic materials with low conductivity are both hard to be reconfigured, and the magnetization of insulative ferrofluids is easily lost once the external magnetic field is removed. A novel reconfigurable ferromagnetic liquid metal (LM) putty-like material (FM-LMP) with high electrical conductivity and transformed shape, which is prepared through homogenously mixing neodymium-iron-boron microparticles into the gallium-based LM matrix, and turning this liquid-like suspension into the solid-like putty-like material by magnetization, is reported to achieve this. The induction magnetic field of FM-LMP is mainly attributed to the magnetic alignment of the dispersed ferromagnetic microparticles, which can be conveniently demagnetized by mechanical disordering and reversibly reconfigured through microparticle realignment by applying a weak magnetic field. FM-LMP with a low fraction of microparticles can be used as printable conductive ink for paper electronics, which are further exploited for applications including magnetic switching, flexible erasable magnetic recording paper, and self-sensing paper-based soft robotics using magnetic actuation.
Most of the existing robots would find it difficult to stretch and transform all parts of their body together due to rigid components and complex actuation mechanisms inside. Here, we presented a highly transformable liquid-metal composite (LMC) that is easy to change shape in large magnitude and resume its original state again according to need. When subject to heating, part of the ethanol droplets embedded in the composite would change phase and then actuate. We demonstrate the flexible transformation of LMC-made octopus from a two-dimensional shape into several predictable three-dimensional shapes freely on a large scale (even up to 11 times its initial height) through remote wireless heating, which needs no sophisticated operating system at all. Further, several designed behaviors, such as movement of octopus and entangling objects of soft robots, are also realized. Theoretical analysis of the heating-induced liquid-vapor transition of the embedded ethanol droplet interprets the mechanisms involved. The present findings open a new way to fabricate functional transformable composites that would find significant applications in developing future generation soft robots.
Materials with a temperature-controlled reversible electrical transition between insulator and conductor are attracting huge attention due to their promising applications in many fields. However, most of them are intrinsically rigid and require complicated fabrication processes. Here, a highly stretchable (680% strain) liquid metal polymer composite as a reversible transitional insulator and conductor (TIC), which is accompanied with huge resistivity changes (more than 4 × 109 times) reversibly through a tuning temperature in a few seconds is introduced. When frozen, the insulated TIC becomes conductive and recovers after warming. Both the phase change of the liquid metal droplets and the rigidity change of the polymer contribute directly to transition between insulator and conductor. A simplified model is established to predict the expansion and connection of liquid metal droplets. Along with high stretchability, straightforward fabrication methods, rapid triggering time, large switching ratio, good repeatability, the TIC offers tremendous possibilities for numerous applications, like stretchable switches, semiconductors, temperature sensors, and resistive random-access memory. Accordingly, a system that can display numbers and letters via converting alternative TIC temperature to a binary signal on a computer is conceived and demonstrated. The present discovery suggests a general strategy for fabricating and stimulating a stretchable transitional insulator and conductor based on liquid metal and allied polymers.
The treatment of hypothermia suffered by naval fighters owing to seawater immersion has been a focus of research in recent years. Currently, the treatment of hypothermia in China is limited to external rewarming, which is of low efficiency and is not effective for patients suffering moderate to severe hypothermia. We thus proposed a vascular interventional heating method which directly heats the blood flow via a minimally invasive heating needle for rewarming. And a numerical simulation using a compartment model based on finite difference method was conducted. A set of whole body heating treatment simulation was also developed. Appropriate treatment parameters and procedures can be set and adjusted based on patient physical parameters. Here temperature response curves of different heating modes were obtained and analyzed. It was demonstrated that the desired thermal response can be achieved by adjusting the heating power and heating time, ensuring controllable accuracy in the treatment of patients with severe hypothermia. The proposed treatment for hypothermia is a new and effective alternative, and further progress is expected in clinical trials.
Cardiovascular Physiological Phenomena , Hypothermia/therapy , Models, Biological , Rewarming/instrumentation , Rewarming/methods , Body Temperature , Humans
BACKGROUND: Thermally significant blood flows into locally cooled diseased tissues and warm them during cryosurgery so that the iceball is often hard to cover the whole diseased volume. This paper is aimed at investigating the effects of large arterial bifurcation on the temperature distribution during cryosurgery through simulation method. METHODS: A parametric geometry model is introduced to construct a close-to-real arterial bifurcation. The three-dimensional transient conjugate heat transfer between bifurcated artery and solid tissues with phase change during cryosurgery is performed by finite volume method. RESULTS: The discussion was then made on the effects of the relative position between cryoprobe and artery bifurcation, the inlet velocity of root artery and the layout of multiple cryoprobes on the temperature distribution and iceball evolution. The results show that the thermal interaction between blood flow and iceball growth near bifurcation is considerable complex. The thermal effects of bifurcation could modulate the iceball morphology, severely weaken its freezing volume and prevent the blood vessel from being frozen. CONCLUSION: The present work is expected to be valuable in optimizing cryosurgery scheme of the situation that the bifurcated artery is embedded into the disease tissue.
Arteries/anatomy & histology , Computer Simulation , Cryosurgery , Temperature , Arteries/physiology , Hemodynamics , Ice , Models, Biological
BACKGROUND: Radio-frequency ablation has been an important physical method for tumor hyperthermia therapy. The conventional rigid electrode boards are often uncomfortable and inconvenient for performing surgery on irregular tumors, especially for those tumors near the joints, such as ankles, knee-joints or other facets like finger joints. MATERIAL AND METHODS: We proposed and demonstrated a highly conformable tumor ablation strategy through introducing liquid metal bath as conformable soft electrodes. Different heights of liquid metal bath electrodes were adopted to perform radio-frequency ablation on targeted tissues. Temperature and ablation area were measured to compare the ablation effect with plate metal electrodes. RESULTS: The recorded temperature around the ablation electrode was almost twice as high as that with the plate electrode and the effective ablated area was 2-3 fold larger in all the mimicking situations of bone tumors, span-shaped or round-shaped tumors. Another unique feature of the liquid metal electrode therapy is that the incidence of heat injury was reduced, which is a severe accident that can occur during the treatment of irregular tumors with plate metal boards. CONCLUSIONS: The present method suggests a new way of using soft liquid metal bath electrodes for targeted minimally invasive tumor ablation in future clinical practice.
Catheter Ablation/instrumentation , Catheter Ablation/methods , Electrodes , Neoplasms/surgery , Alloys , Equipment Design , Humans
The first ever oscillation phenomenon of a copper wire embraced inside a self-powered liquid metal machine is discovered. When contacting a copper wire to liquid metal machine, it would be swallowed inside and then reciprocally moves back and forth, just like a violin bow. Such oscillation could be easily regulated by touching a steel needle on the liquid metal surface.
BACKGROUND: L-proline is a natural, nontoxic cryoprotectant that helps cells and tissues to tolerate freezing in a variety of plants and animals. The use of L-proline in mammalian oocyte cryopreservation is rare. In this study, we explored the cryobiological characteristics of L-proline and evaluated its protective effect in mouse oocyte cryopreservation. METHODS: The freezing property of L-proline was detected by Raman spectroscopy and osmometer. Mature oocytes obtained from 8-week-old B6D2F1 mice were vitrified in a solution consisting various concentration of L-proline with a reduced proportion of dimethyl sulfoxide (DMSO) and ethylene glycol (EG), comparing with the control group (15% DMSO and 15% EG without L-proline). The survival rate, 5-methylcytosine (5-mC) expression, fertilization rate, two-cell rate, and blastocyst rate in vitro were assessed by immunofluorescence and in vitro fertilization. Data were analyzed by Chi-square test. RESULTS: L-proline can penetrate the oocyte membrane within 1 min. The osmotic pressure of 2.00 mol/L L-proline mixture is similar to that of the control group. The survival rate of the postthawed oocyte in 2.00 mol/L L-proline combining 7.5% DMSO and 10% EG is significantly higher than that of the control group. There is no difference of 5-mC expression between the L-proline combination groups and control. The fertilization rate, two-cell rate, and blastocyst rate in vitro from oocyte vitrified in 2.00 mol/L L-proline combining 7.5% DMSO and 10% EG solution are similar to that of control. CONCLUSIONS: It indicated that an appropriate concentration of L-proline can improve the cryopreservation efficiency of mouse oocytes with low concentrations of DMSO and EG, which may be applicable to human oocyte vitrification.
Cryopreservation/methods , Cryoprotective Agents/pharmacology , Oocytes/drug effects , Proline/pharmacology , Animals , Female , Fertilization in Vitro , Hydrogen-Ion Concentration , Male , Mice , Osmotic Pressure , Spectrum Analysis, Raman , Vitrification
Recent studies have shown that L-proline is a natural osmoprotectant and an antioxidant to protect cells from injuries such as that caused by freezing and thawing in many species including plant, ram sperm and human endothelial cells. Nevertheless, this nontoxic cryoprotectant has not yet been applied to mammalian oocyte vitrification. In this study we evaluated the efficiency and safety of the new cryoprotectant in oocyte vitrification. The results indicated that L-proline improves the survival rate of vitrified oocytes, protects mitochondrial functions and could be applied as a new cryoprotectant in mouse oocyte vitrification.
Cryoprotective Agents/pharmacology , Oocytes/drug effects , Proline/pharmacology , Vitrification/drug effects , Animals , Cell Survival/drug effects , Cryopreservation/methods , Cryoprotective Agents/administration & dosage , Dimethyl Sulfoxide/administration & dosage , Embryo Culture Techniques , Embryo Transfer , Embryonic Development/drug effects , Ethylene Glycol/administration & dosage , Female , Male , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Mice, Inbred ICR , Mitochondria/drug effects , Mitochondria/metabolism , Oocytes/cytology , Oocytes/metabolism , Pregnancy , Proline/administration & dosage , Sperm Injections, Intracytoplasmic , Spindle Apparatus/drug effects , Spindle Apparatus/ultrastructure
Driven by the Marangoni effect, a poly(vinyl chloride) (PVC) particle runs in its orbit (a) with high velocity due to the release of surfactant and heat. The PVC particles are also able to efficiently drive an aluminum bulk and to induce spinning and quick runs on a water surface (b).
Cryoablation has been demonstrated powerful in treating of a variety of diseases, especially for the tumor ablation, which destroys the target tissue through the controlled freezing of cryoprobe. The prediction of temperature evolution during cryoablation is of great importance for developing and improving clinical procedure. This paper presented an efficient thermal model to characterize the freezing effect of cryoprobe with arbitrary layout including its size, orientation and number. The key step of the presented model is to establish a boundary heat source method to implicitly characterize the heat transfer from cryoprobe with fixed temperature or convective heat transfer boundary condition, which is furthermore incorporated to a fast parallel alternating direction explicit (PADE) finite difference method for computation acceleration. A novel dynamical and conformal computational region is designed through the shortest distance definition to balance the thermal effect of tissue and computational efficiency. The detailed test cases including a real head tissue demonstrated that the current model can accurately predict the temperature field evolution induced by arbitrary multi-cryoprobe configuration, and achieve significant computational ability due to allowable large time step (100-fold compared with the explicit finite difference method), compact computational region (at least reducing 40% number of voxels) and high parallel efficiency (speedup ratio about 8 for 12 threads) for complex tissue structure.
Cryosurgery/methods , Heating/methods , Models, Theoretical , Freezing , Hot Temperature , Humans , Neoplasms/surgery , Temperature
Internally triggered motion of an object owns important potential in diverse application areas ranging from micromachines, actuator or sensor, to self-assembly of superstructures. A new conceptual liquid metal machine style has been presented here: the transient state machine that can work as either a large size robot, partial running elements, or just divide spontaneously running swarm of tiny motors. According to need, the discrete droplet machines as quickly generated through injecting the stream of a large liquid metal machine can combine back again to the original one. Over the process, each tiny machine just keeps its running, colliding, bouncing, or adhesion states until finally assembling into a single machine. Unlike the commonly encountered rigid machines, such transient state system can be reversible in working shapes. Depending on their surface tension, the autonomously traveling droplet motors can experience bouncing and colliding before undergoing total coalescence, arrested coalescence, or total bounce. This finding would help mold unconventional robot in the sense of transient state machine that could automatically transform among different geometries such as a single or swarm, small or large size, assembling and interaction, etc. It refreshes people's basic understandings on machines, liquid metal materials, fluid mechanics, and micromotors.
