Tunable pheromone interactions among microswimmers.

Indirect interactions via shared memory deposited on the field ("field memory") play an essential role in collective motions. Some motile species, such as ants and bacteria, use attractive pheromones to complete many tasks. Mimicking these kinds of collective behavior at the laboratory scale, we present a pheromone-based autonomous agent system with tunable interactions. In this system, colloidal particles leave phase-change trails reminiscent of the process of pheromone deposition by individual ants, and the trails attract other particles and themselves. To implement this, we combine two physical phenomena: the phase change of a Ge2Sb2Te5 (GST) substrate by self-propelled Janus particles (pheromone deposition) and the AC (alternating current) electroosmotic (ACEO) flow generated by this phase change (pheromone attraction). Laser irradiation causes the GST layer to crystalize locally beneath the Janus particles, owing to the lens heating effect. Under AC field application, the high conductivity of the crystalline trail causes a field concentration and generates ACEO flow, and we introduce this flow as an attractive interaction between the Janus particles and the crystalline trail. By changing the AC frequency and voltage, we can tune the attractive flow, i.e., the sensitivity of the Janus particles to the trail, and the isolated particles undergo diverse states of motion, from self-caging to directional motion. A swarm of Janus particles also shows different states of collective motion, including colony formation and line formation. This tunability enables a reconfigurable system driven by a pheromone-like memory field.

Hybrid Ghost Phonon Polaritons in Thin-Film Heterostructure.

Ghost phonon polaritons (g-PhPs), a unique class of phonon polaritons in the infrared, feature ultralong diffractionless propagation (>20 µm) across the surface and tilted wavefronts in the bulk. Here, we study hybrid g-PhPs in a heterostructure of calcite and an ultrathin film of the phase change material (PCM) In3SbTe2, where the optical field is bound in the PCM film with enhanced confinement compared with conventional g-PhPs. Near-field optical images for hybrid g-PhPs reveal a lemniscate pattern in the momentum distribution. We fabricated In3SbTe2 gratings and investigated how different orientations and periodicities of gratings impact the propagation of hybrid g-PhPs. As the grating period decreases to zero, the wavefront of hybrid g-PhPs can be dynamically steered by varying the grating orientation. Our results highlight the promise of hybrid g-PhPs with tunable functionalities for nanophotonic studies.

Dynamic and Polarization-Independent Wavefront Control Based on Hybrid Topological Metasurfaces.

Exceptional points (EPs), known as non-Hermitian singularities, have been observed and investigated in parity-time symmetric metasurfaces. However, the chirality and tunability in non-Hermitian metasurfaces still need to be explored. Here, we propose a dynamic topological metasurface with the meta-atom consisting of two orthogonally oriented nanorods, which are placed on the phase change material Ge2Sb2Te5 (GST) and SiO2 dielectric layer, respectively. When GST is converted from the amorphous state (a-GST) to the crystalline state (c-GST), an EP can be dynamically switched from the "ON" state to the "OFF" state in a parameter space. Moreover, based on the topologically protected phase and amplitude modulations of the cross-polarization component, the phase-only hologram and amplitude-only hologram are engineered in the a-GST case and concealed in the c-GST case. Finally, we explore the 2D-chiral symmetry of meta-atoms and further propose two spin-selective meta-deflectors and a hybrid meta-deflector operating with arbitrary polarizations. The GST-based hybrid metasurface offers richer possibilities to realize various wavefront controls.

Temperature Self-Limited Intelligent Thermo-chemotherapeutic Lipid Nanosystem for P-gp Reversal Time Window Matched Pulse Treatment of MDR Tumor.

Mild photothermal therapy (PTT) shows the potential for chemosensitization by tumor-localized P-glycoprotein (P-gp) modulation. However, conventional mild PTT struggles with real-time uniform temperature control, obscuring the temperature-performance relationship and resulting in thermal damage. Besides, the time-performance relationship and the underlying mechanism of mild PTT-mediated P-gp reversal remains elusive. Herein, we developed a temperature self-limiting lipid nanosystem (RFE@PD) that integrated a reversible organic heat generator (metal-phenolic complexes) and metal chelator (deferiprone, DFP) encapsulated phase change material. Upon NIR irradiation, RFE@PD released DFP for blocking ligand-metal charge transfer to self-limit temperature below 45 °C, and rapidly reduced P-gp within 3 h via Ubiquitin-proteasome degradation. Consequently, the DOX·HCl-loaded thermo-chemotherapeutic lipid nanosystem (RFE@PD-DOX) led to dramatically improved drug accumulation and 5-fold chemosensitization in MCF-7/ADR tumor models by synchronizing P-gp reversal and drug pulse liberation, achieving a tumor inhibition ratio of 82.42%. This lipid nanosystem integrated with "intrinsic temperature-control" and "temperature-responsive pulse release" casts new light on MDR tumor therapy.

Dressing Paraffin Wax/Boron Nitride Phase Change Composite with a Polyethylene "Underwear" for the Reliable Battery Safety Management.

Phase change material (PCM) can provide a battery system with a buffer platform to respond to thermal failure problems. However, current PCMs through compositing inorganics still suffer from insufficient thermal-transport behavior and safety reliability against external force. Herein, a best-of-both-worlds method is reported to allow the PCM out of this predicament. It is conducted by combining a traditional PCM (i.e., paraffin wax/boron nitride) with a spirally weaved polyethylene fiber fabric, just like the traditional PCM is wearing functional underwear. On the one hand, the spirally continuous thermal pathways of polyethylene fibers in the fabric collaborate with the boron nitride network in the PCM, enhancing the through-plane and in-plane thermal conductivity to 10.05 and 7.92 W m-1 K, respectively. On the other, strong polyethylene fibers allow the PCM to withstand a high puncture strength of 47.13 N and tensile strength of 18.45 MPa although above the phase transition temperature. After this typical PCM packs a triple Li-ion battery system, the battery can be promised reliable safety management against both thermal and mechanical abuse. An obvious temperature drop of >10 °C is observed in the battery electrode during the cycling charging and discharging process.

Uncovering Temperature-Insensitive Feature of Phase Change Thermal Storage Electrolyte for Safe Lithium Battery.

Lithium-ion batteries (LIBs) have emerged as highly promising energy storage devices due to their high energy density and long cycle life. However, their safety concern, particularly under thermal shock, hinders their widespread applications. Herein, a temperature-insensitive electrolyte (TI-electrolyte) with exceptional resistance to thermal stimuli is presented to address the safety issues arising from the lack of thermal abuse tolerance in LIBs. The TI-electrolyte is composed of two phase-change polymers with differentiation melting points (60 and 35°C for polycaprolactone and polyethylene glycol respectively), delivering a wide temperature-resistant range. It is demonstrated that the TI-electrolyte possesses a heat capacity of 27.3 J g-1. The crystalline region in the TI-electrolyte shrinks when confronted with above-ambient temperature, absorbing heat to unlock molecular chains fixed in the crystal lattice, becoming amorphous. Notably, the Li||LFP pouch cell delays 3 valuable minutes to achieve the same temperature as conventional liquid electrolytes (LE) when subjected to thermal shocks, paralleling with the simulation results. Moreover, symmetrical Li||Li cell cycles stably for over 600 h at 0.1 mA cm-2, and Li||LFP full cell demonstrates excellent electrochemical performance, with a capacity of 142.7 mAh g-1 at 0.5 C, thus representing a critical approach to enhancing the safety of LIBs.

Highly Tunable Cellulosic Hydrogels with Dynamic Solar Modulation for Energy-Efficient Windows.

Smart windows that can passively regulate incident solar radiation by dynamically modulating optical transmittance have attracted increasing scientific interest due to their potential economic and environmental savings. However, challenges remain in the global adoption of such systems, given the extreme variability in climatic and economic conditions across different geographical locations. Aiming these issues, a methylcellulose (MC) salt system is synthesized with high tunability for intrinsic optical transmittance (89.3%), which can be applied globally to various locations. Specifically, the MC window exhibits superior heat shielding potential below transition temperatures, becoming opaque at temperatures above the Lower Critical Solution Temperature and reducing the solar heat gain by 55%. This optical tunability is attributable to the particle size change triggered by the temperature-induced reversible coil-to-globular transition. This leads to effective refractive index and scattering modulation, making them prospective solutions for light management systems, an application ahead of intelligent fenestration systems. During the field tests, MC-based windows demonstrated a 9 °C temperature decrease compared to double-pane windows on sunny days and a 5 °C increase during winters, with simulations predicting an 11% energy savings. The ubiquitous availability of materials, low cost, and ease-of-manufacturing will provide technological equity and foster the ambition toward net-zero buildings.

Phase Engineered Composite Phase Change Materials for Thermal Energy Manipulation.

Phase change materials (PCMs) present a dual thermal management functionality through intrinsic thermal energy storage (TES) capabilities while maintaining a constant temperature. However, the practical application of PCMs encounters challenges, primarily stemming from their low thermal conductivity and shape-stability issues. Despite significant progress in the development of solid-solid PCMs, which offer superior shape-stability compared to their solid-liquid counterparts, they compromise TES capacity. Herein, a universal phase engineering strategy is introduced to address these challenges. The approach involves compositing solid-liquid PCM with a particulate-based conductive matrix followed by surface reaction to form a solid-solid PCM shell, resulting in a core-shell composite with enhanced thermal conductivity, high thermal storage capacity, and optimal shape-stability. The core-shell structure designed in this manner not only encapsulates the energy-rich solid-liquid PCM core but also significantly enhances TES capacity by up to 52% compared to solid-solid PCM counterparts. The phase-engineered high-performance PCMs exhibit excellent thermal management capabilities by reducing battery cell temperature by 15 °C and demonstrating durable solar-thermal-electric power generation under cloudy or no sunshine conditions. This proposed strategy holds promise for extending to other functional PCMs, offering a compelling avenue for the development of high-performance PCMs for thermal energy applications.

An Innovative Azobenzene-Based Photothermal Fabric with Excellent Heat Release Performance for Wearable Thermal Management Device.

Azobenzene (azo)-based photothermal energy storage systems have garnered great interest for their potential in solar energy conversion and storage but suffer from limitations including rely on solvents and specific wavelengths for charging process, short storage lifetime, low heat release temperature during discharging, strong rigidity and poor wearability. To address these issues, an azo-based fabric composed of tetra-ortho-fluorinated photo-liquefiable azobenzene monomer and polyacrylonitrile fabric template is fabricated using electrospinning. This fabric excels in efficient photo-charging (green light) and discharging (blue light) under visible light range, solvent-free operation, long-term energy storage (706 days), and good capacity of releasing high-temperature heat (80-95 °C) at room temperature and cold environments. In addition, the fabric maintains high flexibility without evident loss of energy-storage performance upon 1500 bending cycles, 18-h washing or 6-h soaking. The generated heat from charged fabric is facilitated by the Z-to-E isomerization energy, phase transition latent heat, and the photothermal effect of 420 nm light irradiation. Meanwhile, the temperature of heat release can be personalized for thermal management by adjusting the light intensity. It is applicable for room-temperature thermal therapy and can provide heat to the body in cold environments, that presenting a promising candidate for wearable personal thermal management.

Plasmonic switches based on VO2as the phase change material.

In this paper, a comprehensive review of the recent advancements in the design and development of plasmonic switches based on vanadium dioxide (VO2) is presented. Plasmonic switches are employed in applications such as integrated photonics, plasmonic logic circuits and computing networks for light routing and switching, and are based on the switching of the plasmonic properties under the effect of an external stimulus. In the last few decades, plasmonic switches have seen a significant growth because of their ultra-fast switching speed, wide spectral tunability, ultra-compact size, and low losses. In this review, first, the mechanism of the semiconductor to metal phase transition in VO2is discussed and the reasons for employing VO2over other phase change materials for plasmonic switching are described. Subsequently, an exhaustive review and comparison of the current state-of-the-art plasmonic switches based on VO2proposed in the last decade is carried out. As the phase transition in VO2can be activated by application of temperature, voltage or optical light pulses, this review paper has been categorized into thermally-activated, electrically-activated, and optically-activated plasmonic switches based on VO2operating in the visible, near-infrared, infrared and terahertz frequency regions.

Reversible Thermally Driven Phase Change of Layered In2Se3 for Integrated Photonics.

Two-dimensional In2Se3, an unconventional phase-change material, has drawn considerable attention for polymorphic phase transitions and electronic device applications. However, its reversible thermally driven phase transitions and potential use in photonic devices have yet to be explored. In this study, we observe the thermally driven reversible phase transitions between α and ß' phases with the assistance of local strain from surface wrinkles and ripples, as well as reversible phase changes within the ß phase family. These transitions lead to changes in the refractive index and other optoelectronic properties with minimal optical loss at telecommunication bands, which are crucial in integrated photonic applications such as postfabrication phase trimming. Additionally, multilayer ß'-In2Se3 working as a transparent microheater proves to be a viable option for efficient thermo-optic modulation. This prototype design for layered In2Se3 offers immense potential for integrated photonics and paves the way for multilevel, nonvolatile optical memory applications.

Enhancing physiological recovery and subsequent exercise performance in the heat using a phase-change material cooling blanket.

This study aimed to assess the effect of a phase-change material (PCM) cooling blanket for cooling between exercise bouts on recovery of physiological parameters and subsequent exercise performance in the heat. Eighteen male volunteers were recruited to participate in human trials involving two exhaustive treadmill running bouts (Bout1 for 3 km and Bout2 for 1.5 km) in a climate chamber (temperature = 33 °C; relative humidity = 40%). Participants were randomly subjected to one of two cooling conditions for a 10-min period between exercise bouts: CON: natural cooling; 10-min PCM: with a PCM cooling blanket for 10 min. Several physiological parameters including mean skin temperature (Tskin), oral temperature (Toral), core temperature (Tcore), heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peripheral capillary oxygen saturation (SpO2), average running speed and rating of perceived exertion (RPE) scale score were analyzed. The results showed that compared to the CON group, participants in the 10-min PCM group had a significant lower Tskin, Tcore, HR and RR at post-cooling, as well as greater reductions in mean skin temperature (ΔTskin) and core temperature (ΔTcore) from post-Bout1 to post-cooling. Additionally, the 10-min PCM group exhibited significantly lower peak Tcore, peak HR and RPE scale score during Bout2, while the average running speed during Bout2 was significantly higher. The present study suggests that cooling with a PCM cooling blanket can enhance physiological recovery and subsequent exercise performance in the heat.

A Eulerian Numerical Model to Predict the Enhancement Effect of the Gravity-Driven Motion Melting Process for Latent Thermal Energy Storage.

Latent thermal energy storage (LTES) devices can efficiently store renewable energy in thermal form and guarantee a stable-temperature thermal energy supply. The gravity-driven motion melting (GDMM) process improves the overall melting rate for packaged phase-change material (PCM) by constructing an enhanced flow field in the liquid phase. However, due to the complex mechanisms involved in fluid-solid coupling and liquid-solid phase transition, numerical simulation studies that demonstrate physical details are necessary. In this study, a simplified numerical model based on the Eulerian method is proposed. We aimed to introduce a fluid deformation yield stress equation to the "solid phase" based on the Bingham fluid assumption. As a result, fluid-solid coupling and liquid-solid phase transition processes become continuously solvable. The proposed model is validated by the referenced experimental measurements. The enhanced performance of liquid-phase convection and the macroscopic settling of the "solid phase" are numerically analyzed. The results indicate that the enhanced liquid-phase fluidity allows for a stronger heat transfer process than natural convection for the pure liquid phase. The gravity-driven pressure difference is directly proportional to the vertical melting rate, which indicates the feasibility of controlling the pressure difference to improve the melting rate.

Polyethylene glycol with dual three-dimensional porous carbon nanotube/diamond: a high thermal conductivity of composite PCM.

Polyethylene glycol (PEG) is widely used as a phase change material (PCM) in thermal energy storage systems due to its high latent heat and chemical stability. However, practical application has been hindered by its low thermal conductivity and leakage issues. Therefore, developing shape-stable high thermal conductivity PCM is of great importance. In this study, new shape-stable composite PCM with high thermal conductivity and leak-prevention capabilities were designed. The porous carbon skeleton of diamond foam (DF) and dual-3D carbon nanotube-diamond foam (CDF) were prepared using the microwave plasma chemical vapor deposition method. The composite materials (DF/PEG and CDF/PEG) were produced by vacuum impregnation with PEG and skeletons. The results showed that CDF/PEG had the highest thermal conductivity, measuring 2.30 W·m-1·K-1, which is 707% higher than that of pure PEG. The employing of 3D networks of CNTs, which can improve the phonon mean free path in DF/PEG (1.79 W·m-1·K-1) while reducing phonon dispersion.The phonon vibration of dual-3D CDF plays an important role in heat transfer. PEG was physically absorbed and well-distributed in CDF, alleviating leakage of liquid PEG. The weight loss of CDF/PEG was only 25% at 70 °C for 120 s. Using CDF is an attractive and efficient strategy to increase the heat transfer of PEG and improve heat storage efficiency, alleviate the problem of poor shape-stability.

Visible-Band Chiroptical Meta-devices with Phase-Change Adjusted Optical Chirality.

Low-cost large-area chirality meta-devices (CMDs) with adjustable optical chirality are of great interest for polarization-sensitive imaging, stereoscopic display, enantioselectivity analysis, and catalysis. Currently, CMDs with adjusted chiroptical responses in the mid-infrared to terahertz band have been demonstrated by exploiting photocarriers of silicon, pressure, and phase-change of GSTs but are still absent in the visible band, which in turn limits the development of chiral nanophotonic devices. Herein, by employing a phase-change material (Sb2S3), we present a protocol for the fabrication of wafer-scale visible-band enantiomeric CMDs with handedness, spectral, and polarization adjustability. As measured by circular dichroism, the chirality signs of CMDs enantiomers can be adjusted with Sb2S3 from amorphous to crystalline, and the chirality resonance wavelength can also be adjusted. Our results suggest a new type of meta-devices with adjustable chiroptical responses that may potentially enable a wide range of chirality nanophotonic applications including highly sensitive sensing and surface-enhanced nanospectroscopy.

Thermo-kinetic behaviour of green synthesized nanomaterial enhanced organic phase change material: Model fitting approach.

Metal, carbon and conducting polymer nanoparticles are blended with organic phase change materials (PCMs) to enhance the thermal conductivity, heat storage ability, thermal stability and optical property. However, the existing nanoparticle are expensive and need to be handle with high caution during operation as well during disposal owing to its toxicity. Subsequently handling of solid waste and the disposal of organic PCM after longevity usage are of utmost concern and are less exposed. Henceforth, the current research presents a new dimension of exploration by green synthesized nanoparticles from a thorny shrub of an invasive weed named Prosopis Juliflora (PJ) which is a agro based solid waste. Subsequently, the research is indented to decide the concentration of green synthesized nanoparticle for effective heat transfer rate of organic PCM (Tm = 35-40 °C & Hm = 145 J/g). Furthermore, an in-depth understanding on the kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM after usage via Coats and Redfern technique is exhibited. Engaging a two-step method, we fuse the green synthesized nanomaterial with PCM to obtain nanocomposite PCM. On experimental evaluation, thermal conductivity of the developed nanocomposite (PCM + PJ) increases by 63.8% (0.282 W/m⋅K to 0.462 W/m⋅K) with 0.8 wt% green synthesized nanomaterial owing to the uniform distribution of nanoparticle within PCM matrix thereby contributing to bridging thermal networks. Subsequently, PCM and PCM + PJ nanocomposites are tested using thermogravimetric analyzer at different heating rates (05 °C/min; 10 °C/min; 15 °C/min & 20 °C/min) to analyze the decomposition kinetic reaction. The kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM and its nanocomposite of PCM + PJ provides insight on thermal parameters to be considered on large scale operation and to understand the complex nature of the chemical reactions. Adopting thirteen different chemical mechanism model under Coats and Redfern method we determine the reaction mechanism; kinetic parameter like activation energy (Ea) & pre-exponential factor (A) and thermodynamic parameter like change in enthalpy (ΔH), change in Gibbs free energy (ΔG) and change in entropy (ΔS). Dispersion of PJ nanomaterial with PCM reduces Ea from 370.82 kJ/mol-1 to 342.54 kJ/mol-1 (7.7% reduction), as the developed nanomaterial is enriched in carbon element and exhibits a catalytic effect for breakdown reaction. Corresponding, value of ΔG for PCM and PCM + PJ sample within heating rates of 05-20 °C/min varies between 168.95 and 41.611 kJ/mol-1. The current research will unbolt new works with focus on exploring the pyrolysis behaviour of phase change materials and its nanocomposite used for energy storage applications. This work also provides insights on the disposal of PCM which is an organic solid waste. The thermo-kinetic profile will help to investigate and predict the optimum heating rate and temperature range for conversion of micro-scale pyrolysis to commercial scale process.

Modified Technogenic Asphaltenes as Enhancers of the Thermal Conductivity of Paraffin.

The low thermal conductivity of paraffin and other organic phase change materials limits their use in thermal energy storage devices. The introduction of components with a high thermal conductivity such as graphene into these materials leads to an increase in their thermal conductivity. In this work, we studied the use of inexpensive carbon fillers containing a polycyclic aromatic core, due to them having a structural similarity with graphene, to increase the thermal conductivity of paraffin. As such fillers, technogenic asphaltenes isolated from ethylene tar and their modified derivatives were used. It is shown that the optimal concentration of carbon fillers in the paraffin composite, which contributes to the formation of a structural framework and resistance to sedimentation, is 5 and 30 wt. %, while intermediate concentrations are ineffective, apparently due to the formation of large aggregates, the concentration of which is insufficient to form a strong framework. It has been found that the addition of asphaltenes modified with ammonium persulfate in acetic acid significantly increases the thermal conductivity of paraffin by up to 72%.

Modified Supporting Materials to Fabricate Form Stable Phase Change Material with High Thermal Energy Storage.

Thermal energy storage (TES) is vital to the absorption and release of plenty of external heat for various applications. For such storage, phase change material (PCM) has been considered as a sustainable energy material that can be integrated into a power generator. However, pure PCM has a leakage problem during the phase transition process, and we should fabricate a form stable PCM composite using some supporting materials. To prevent the leakage problem during the phase transition process, two different methods, microencapsulation and 3D porous infiltration, were used to fabricate PCM composites in this work. It was found that both microsphere and 3D porous aerogel supported PCM composites maintained their initial solid state without any leakage during the melting process. Compared with the microencapsulated PCM composite, the 3D porous aerogel supported PCM exhibited a relatively high weight fraction of working material due to its high porosity. In addition, the cross-linked graphene aerogel (GCA) could reduce volume shrinkage effectively during the infiltration process, and the GCA supported PCM composite kept a high latent heat (∆H) and form stability.

Kinetic Monte Carlo simulations of Ge-Sb-Te thin film crystallization.

Simulation of atomic redistribution in Ge-Sb-Te (GST)-based memory cells during SET/RESET cycling is needed in order to understand GST memory cell failure and to design improved non-volatile memories. However, this type of atomic scale simulations is extremely challenging. In this work, we propose to use a simplified GST system in order to catch the basics of atomic redistribution in Ge-rich GST (GrGST) films using atomistic kinetic Monte Carlo simulations. Comparison between experiments and simulations shows good agreements regarding the influence of Ge excess on GrGST crystallization, as well as concerning the GST growth kinetic in GrGST films, suggesting the crystallized GST ternary compound to be off-stoichiometric. According to the simulation of atomic redistribution in GrGST films during SET/RESET cycling, the film microstructure stabilized during cycling is significantly dependent of the GST ternary phase stoichiometry. The use of amorphous layers exhibiting the GST ternary phase stoichiometry placed at the bottom or at the top of the GrGST layer is shown to be a way of controlling the microstructure evolution of the film during cycling. The significant evolution of the local composition in the amorphous solution during cycling suggests a non-negligible variation of the crystallization temperature with operation time.

Cold for centuries: a brief history of cryotherapies to improve health, injury and post-exercise recovery.

For centuries, cold temperatures have been used by humans for therapeutic, health and sporting recovery purposes. This application of cold for therapeutic purposes is regularly referred to as cryotherapy. Cryotherapies including ice, cold-water and cold air have been popularised by an ability to remove heat, reduce core and tissue temperatures, and alter blood flow in humans. The resulting downstream effects upon human physiologies providing benefits that include a reduced perception of pain, or analgesia, and an improved sensation of well-being. Ultimately, such benefits have been translated into therapies that may assist in improving post-exercise recovery, with further investigations assessing the role that cryotherapies can play in attenuating the ensuing post-exercise inflammatory response. Whilst considerable progress has been made in our understanding of the mechanistic changes associated with adopting cryotherapies, research focus tends to look towards the future rather than to the past. It has been suggested that this might be due to the notion of progress being defined as change over time from lower to higher states of knowledge. However, a historical perspective, studying a subject in light of its earliest phase and subsequent evolution, could help sharpen one's vision of the present; helping to generate new research questions as well as look at old questions in new ways. Therefore, the aim of this brief historical perspective is to highlight the origins of the many arms of this popular recovery and treatment technique, whilst further assessing the changing face of cryotherapy. We conclude by discussing what lies ahead in the future for cold-application techniques.