Low Transition Temperature Research Articles

Investigation of the structural and magnetic properties of the GdCoC compound featuring excellent cryogenic magnetocaloric performance

Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) has been recognized as an environmentally benign and energy-efficient cooling technology. Exploring suitable magnetocaloric materials is a crucial prerequisite for practical MR applications. We have herein provided a systematic investigation of the crystal structure, microstructure, electronic structure, magnetic phase transition, critical behavior, and MCE of the GdCoC compound featuring excellent cryogenic magnetocaloric performance by means of experimental determination and theoretical calculation. The GdCoC compound is crystallized in a simple layered tetragonal crystal structure with a P42/mmc space group and undergoes two successive ferromagnetic (FM) transitions along with a low-temperature weak antiferromagnetic (AFM) transition under low magnetic fields. Density functional theory calculations confirms the FM coupling of the Gd and Co intra-sublattice interactions, whereas AFM coupling for their inter-sublattice interaction. The magnetic transitions are merged in to one under high magnetic fields which has been confirmed to be second-order type and its critical behavior can be understood in the framework of tri-critical mean-field model, whereas the low-temperature weak AFM transition is belonging to the first-order type. The excellent magnetocaloric performance of the GdCoC compound was identified by the parameters of magnetic entropy change, adiabatic temperature change, temperature-averaged entropy change, relative cooling power, and refrigerant capacity, which are superior to most of the well-known magnetocaloric materials with similar working temperatures, making it attractive for practical cryogenic MR applications.

A light/thermal cascaded-driven equipment for machine recognition inspired by water lilies using as multifunctional soft actuator

Inspired by the natural stimulus–response of plants and animals, a range of soft equipment has been extensively developed and used in intelligent human–computer interaction, editable remote drives, and machine learning. Poly(N-isopropyl acrylamide) (PNIPAM) hydrogels have gained popularity thanks to their low phase transition temperature and excellent flexibility. However, the PNIPAM hydrogels suffer from poor mechanical properties, low electrical conductivity, and lack of self-responsiveness. Herein, a bilayer light/thermal cascaded-driven anisotropic poly acrylamide/poly(N-isopropylacrylamide-co-acrylamide)-polyvinyl alcohol-MXene (P/PP-M) actuator was prepared by a simple two-step polymerization method. The unique bionic light/thermal response mechanism enables rapid conversion of energy forms and the construction of remote editable actuators. Concretely, the mechanical properties of hydrogels (strain: 1014 %, stress: 94 KPa) have been greatly improved by copolymerizing MXene nanosheets and multiplex hydrogels through two-by-two interpenetrating molecular chains. MXene nanosheets formed dynamic networks conferring the hydrogel system with high conductivity and light/thermal conversion efficiency. The P/PP-M soft actuator features high sensitivity (Gauge factor = 3.62), fast response time (400 ms), and cycling durability (>500 cycles). Finally, the energy transfer mechanism from light to thermal energy to kinetic energy was corroborated by preparing a series of bionic equipment. Manual clips were prepared on this basis, which enables the transportation of objects and realizes the real-time reflection of the operating status of remotely driven soft manual clips through changes in electrical signals. Thus, the proposed efficient editable remote-driven machine recognition soft equipment provides new insights for developing intelligent flexible robots and wearable smart devices.

Magnetic properties of Dy[formula omitted](Co,Ni) compounds at ambient and high pressures

Dy3Co, in addition to two antiferromagnetic (AFM) transitions (35 K and TN∼ 44 K), exhibits a Griffiths-like phase around 65 K and it persists up to ∼1 GPa pressure. External pressure alters the magnetic state significantly and results in increase (decrease) of TN (TAF) by 6.5% (∼13%) with dTN/dP ∼ 3 K/GPa (dTAF/dP ∼ −4.5 K/GPa). Increase in metamagnetic critical field and other changes with pressure indicate the strengthening of AFM interactions in Dy3Co. On the other hand, Dy3Ni shows three magnetic transitions at To∼ 55 K, T1∼ 39 K (AFM) and T2∼ 24 K (AFM). Experimental evidence points to the magnetic ordering temperature to be at To∼55 K instead of 39 K as claimed by certain reports. External pressure reduces (increases) the transition temperature To (T1) by ∼7.9% (7.6%) at a rate of −3.5 K/GPa (2.5 K/GPa). Pressure has only marginal effect on the other low temperature transition at T2. Additionally, ac-susceptibility data exhibit spin-glass like features, which seem to arise from domain wall movements and probably random freezing of small components of spins, coexisting with dominant long-ranged non-collinear AFM structure in these compounds.

Probing the Band Splitting near the Γ Point in the van der Waals Magnetic Semiconductor CrSBr.

This study investigates the electronic band structure of chromium sulfur bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis on the PL data robustly unveils energy splittings, band gaps, and excitonic transitions across different thicknesses of CrSBr, from monolayer to bulk. Temperature-dependent PL measurements elucidate the stability of the band splitting below the Néel temperature, suggesting that magnons coupled with excitons are responsible for the symmetry breaking and brightening of the transitions from the secondary conduction band minimum (CBM2) to the global valence band maximum (VBM1). Collectively, these results not only reveal splitting in both the conduction and valence bands but also highlight a significant advance in our understanding of the interplay between the optical, electronic, and magnetic properties of antiferromagnetic two-dimensional van der Waals crystals.

Antimony doping towards fast digital encryption and decryption and high-efficiency WLED in zero-dimensional hybrid indium chlorides

Lead-free metal halides with thermally induced reversible fluorescence transitions are promising smart optoelectronic materials. However, it is challenging to obtain such materials with reversible and fast fluorescent thermochromism at relatively low temperatures. Herein, two series of new zero-dimensional (0-D) hybrid perovskite indium chlorides doped with Sb3+ are synthesized and characterized, namely (TAEA)InCl6·Cl·4H2O: xSb3+ (1: xSb3+) and (TETA)InCl6·Cl·H2O: xSb3+ (2: xSb3+) (TAEA = quadruply protonated tris(aminoethyl)amine; TETA = quadruply protonated triethylenetetramine; x = 0 − 15 %). Compound 1: 0.5 %Sb3+ displays green broadband emission with photoluminescence quantum yield (PLQY) of 44.4 %, while compound 2: 1 %Sb3+ produces yellow emission with PLQY of 73.46 %. A reversible transition between green and orange light emission for 1: 0.5 %Sb3+ can be triggered by thermal stimulation; such photoluminescence (PL) color switching happens with a fast response time of 20 s and a low transition temperature of 333 K. In addition, the materials combining compounds 2: 1 %Sb3+ and 1: 0.5 %Sb3+ can achieve complex digital encryption and decryption upon heating. Furthermore, due to its excellent luminous efficiency, the 2: 1 %Sb3+ is employed as yellow phosphor for white light-emitting diode (WLED). The WLED shows a CRI of 90.5 and a CCT of 5415 K, superior to most WLEDs based on hybrid metal halides. Finally, the impact of forming the self-trapped excitons state and complex PL mechanism of compound 1: 0.5 %Sb3+ are investigated through DFT calculations and femtosecond transient absorption techniques. This work provides new insights into the design of hybrid metal halides with multiple optical properties, paving the way to obtaining materials for multiple optical applications.

Enhanced visible transmittance with low phase transition temperature of VO2 enabled by W-Mg co-doping

Vanadium dioxide (VO2) is a promising thermochromic material for smart windows. However, the relatively high phase transition temperature (Tt) and low visible transmittance (Tlum) constrain its practical application. Cationic co-doping offers an effective strategy to optimize the optical switching properties near room temperature. In this line, herein, the W-Mg co-doped VO2 films were synthesized by a solution and annealing method from W-Mg co-doped ammonium citrato-oxovanadate (IV). The synergistic effect of W-Mg co-doping improves the performance of VO2 films with Tt of 42.6 °C, Tlum of 59.0 % and solar energy modulation of 12.8 %. By changing the amounts of Mg, the W-Mg co-doped VO2 film maintains the low Tt of W-VO2 film and meanwhile possesses higher Tlum, which is attributed to the band gap structure change induced by the W-Mg co-doping. The excellent optical, thermochromic and thermal insulation performances confirm that our research could provide guidance for advancing the application of VO2 in smart window fields.

Spin flop transitions and complex magnetic behaviour in CoMoO4 powders and [formula omitted]-CoMoO4 thin films

Magnetic measurements were made on α-CoMoO4 powder and β-CoMoO4 thin film samples. α-CoMoO4 powder showed antiferromagnetic ordering below 13 K and two sharp spin flop transitions with complete magnetic saturation after the second transition (>5 T). A magnetic phase diagram for α-CoMoO4 was constructed, revealing three low-temperature magnetic phases: an antiferromagnetic phase at low field, an intermediate spin-flop phase, and a paramagnetic phase at high field. Two well-defined magnetisation plateaus were observed either side of the spin-flop phase: the first occurred with a moment per Co ion of 1/3 of spin saturation (where Co moments are completely aligned to the applied magnetic field), whereas the second occurred at a moment per Co ion matching calculations for spin saturation (3 μB per Co). No geometric origin for this factor of 1/3 could be found. Hysteresis was observed around the first spin-flop transition, indicating the presence of spin canting or magnetic domains under an applied field. The first successful fabrication of CoMoO4 thin films was achieved via RF magnetron sputtering, yielding β phase films which remain in the β phase upon cooling. The β-CoMoO4 thin films demonstrated antiferromagnetic ordering below 10 K. While two spin-flop transitions are seen in the β phase films (with a hysteresis around the first), spin saturation is not reached in fields up to 6 T, suggesting the existence of a third spin reorientation at higher field. A magnetic phase diagram was also constructed for the β-CoMoO4 film, which demonstrated the same three low-temperature magnetic phases, though with lower critical fields and transition temperatures. Comparisons with isostructural Ni and Mn molybdates showed that the key differences in the α and β phases arise from the different coordination of the Mo tetramers, indicating differences in magnetic properties in both phases arise from variations in the inter-tetramer exchange coupling.

Effects of Composition and Polymerization Conditions on the Electro-Optic Performance of Liquid Crystal-Polymer Composites Doped with Ferroelectric Nanoparticles.

The presence of a polymer network and/or the addition of ferroelectric nanoparticles to a nematic liquid crystal are found to lower transition temperatures and birefringence, which indicates reduced orientational order. In addition, the electro-optic switching voltage is considerably increased when a polymer network is formed by in situ polymerization in the nematic state. However, the resulting polymer network liquid crystal switches at similar voltages as the neat liquid crystal when polymerization is performed at an elevated temperature in the isotropic state. When nanoparticle dispersions are polymerized at an applied DC voltage, the transition temperatures and switching voltages are reduced, yet they are larger than those observed for polymer network liquid crystals without nanoparticles polymerized in the isotropic phase.

Experimental assessment of the heat shielding performance by the integration of phase change material and liquid cooling plate

This research focuses on innovative stealth equipment by integrating a liquid cooling plate and phase change material (PCM), and the temperature rise on the cold surface and PCM melting rate is reported to illustrate the PCM thermal behavior in lifting the heat shielding performance. Results show that the integrated PCM system is effective in delaying the temperature rise within a certain time. A slower temperature rise on the cold surface is found at the first 1200 s, and a significant acceleration in the temperature rise is given within 1200 s ∼ 2000 s as the heat flood breaks through the PCM layer. The PCM melting rate increases rapidly and then rises slowly, and the complete melting time is shortened as increasing heat power. The heat shielding performance is significantly reduced with increasing the liquid flow rate, and the influence of the coolant temperature on the temperature rise becomes more and more prominent as the completion of the PCM melting process. A slower temperature rise is observed at the lower PCM phase transition temperature, and a further increase in the PCM covering layer has little influence on the temperature rise at the initial stage.

Stabilizing a low temperature phase change material based on Glaubers salt

The aim of this research is to enhance the performance of Glauber's salt (sodium sulfate decahydrate, SSD) as a phase change material (PCM) for thermal energy storage applications, as well as for shipping of temperature-sensitive materials. The study investigates the effects of modifying SSD with potassium chloride (KCl) and ammonium chloride (NH4Cl) to achieve lower phase transition temperatures of between +6 °C and + 13 °C. Sodium polyacrylate (PAAS) is employed as a thickening agent to prevent phase separation, and borax is used as a nucleating agent to suppress supercooling. Various ratios of KCl:NH4Cl are tested, and the impact of PAAS concentration on phase segregation is explored. The results show that a 2 wt% concentration of PAAS effectively prevents phase separation. Samples with a KCl:NH4Cl ratio of 1:1.83 exhibit stable phase transition behavior and maintain latent heat values within the range of 130–140 J/g after 30 thermal cycles. Maintaining a total KCl and NH4Cl proportion of 10 wt% is crucial to achieve the desired lower melting temperature. The study highlights the significance of thermal cycling in improving the stability of the PCM. The optimized SSD-based eutectic PCM formulations hold promise for applications in the cold chain industry.

A Thermally Reconfigurable Photonic Switch Utilizing Drop Cast Vanadium Oxide Nanoparticles on Silicon Waveguides

Photonic switches play a vital role in optical communications and computer networks for establishing and releasing connections of optical signals. With the growing demand for ultra‐compact switches in high‐speed optical computing and communications, thermally reconfigurable optical switches have gained significant attention. These switches offer simplicity, ease of fabrication, and leverage a wide range of thermo‐optic materials. Silicon remains an ideal platform for making photonic devices including the switches due to its compatibility with complementary metal‐oxide‐semiconductor (CMOS) technology and cost‐effectiveness. The article presents a drop cast sub‐stoichiometric vanadium oxide (VO2−x) nanoparticles combined with a silicon ridge waveguide to make a compact thermally reconfigurable optical switch with low transition temperature and accelerated phase transition. Furthermore, the design achieves high modulation depth in addition to its scalability and simplicity. This study demonstrates the potential of solution‐based VO2−x nanoparticles in combination with silicon waveguides for efficient optical switch design for various applications.

Microstructure evolution and mechanical properties of β/γ-TiAl alloy during high-rate near-isothermal multidirectional forging

The microstructure of β/γ-TiAl alloy was characterized and analyzed in various deformation regions during a high-rate near-isothermal multidirectional forging (HR-NIMDF) process in this study. The results indicate that the localized precipitation of the B2 phase occurs within the large lamella microstructure through DRX and heterogeneous exsolution decomposition mechanism in the stagnant zone. The majority of mixed fine-grained microstructures (α2/γ/B2), with a grain diameter smaller than 1 μm, were formed under an appropriate stress-temperature coupling field. In the central region of the large deformation zone, a small twisted lamellar microstructure with low B2 phase content is observed, suggesting that HR-NIMDF can efficiently decompose the (α2/γ) lamellar structure and achieve refined grain microstructures. After undergoing HR-NIMDF, the β/γ-TiAl alloy exhibits a low tough-brittle transition temperature and an elongation of 7 % at 650 °C, with an ultimate tensile strength of 862.6 MPa. At 700 °C, the elongation increases to 55.4 %, while the ultimate tensile strength decreases to 653.8 MPa. Moreover, this study demonstrates that when the plastic deformation degree is insufficient and the adiabatic warming effect is relatively pronounced, significant precipitation of the B2 phase leads to a reduction in DRX extent within the material, ultimately resulting in the formation of large residual (α2/γ) lamellar microstructure. The unsynchronized thermal-force coupling relationship between the precipitation of the B2 phase and DRX holds significant implications for advancing and refining the thermoplastic deformation process of β/γ-TiAl alloy.

Low-Temperature Nanosecond Laser Process of HZO-IGZO FeFETs toward Monolithic 3D System on Chip Integration.

Ferroelectric field-effect transistors (FeFETs) are increasingly important for in-memory computing and monolithic 3D (M3D) integration in system-on-chip (SoC) applications. However, the high-temperature processing required by most ferroelectric memories can lead to thermal damage to the underlying device layers, which poses significant physical limitations for 3D integration processes. To solve this problem, the study proposes using a nanosecond pulsed laser for selective annealing of hafnia-based FeFETs, enabling precise control of heat penetration depth within thin films. Sufficient thermal energy is delivered to the IGZO oxide channel and HZO ferroelectric gate oxide without causing thermal damage to the bottom layer, which has a low transition temperature (<250 °C). Using optimized laser conditions, a fast response time (<1 µs) and excellent stability (cycle >106, retention >106 s) are achieved in the ferroelectric HZO film. The resulting FeFET exhibited a wide memory window (>1.7V) with a high on/off ratio (>105). In addition, moderate ferroelectric properties (2·Pr of 14.7 µCcm-2) and pattern recognition rate-based linearity (potentiation: 1.13, depression: 1.6) are obtained. These results demonstrate compatibility in HZO FeFETs by specific laser annealing control and thin-film layer design for various structures (3D integrated, flexible) with neuromorphic applications.

Room-temperature superelasticity in Mg–Sc shape memory alloys revealed by first-principles calculations

The discovery of the Mg–Sc shape memory alloy system has become a milestone in the development of lightweight shape memory alloys. However, for the application scenarios with the highest demand at room temperature, the Mg–Sc alloy faces problems such as excessively low phase transition temperatures and poor room-temperature superelasticity, directly hindering the practical application of this new type of lightweight memory alloy. In this work, Mg–Sc based shape memory alloys with exceptional room temperature superelasticity have been screened for the first time utilizing Tm, phase transformation strain, and stress-strain curves. Co and Ge are selected as the most promising elements for improving Mg–Sc based alloys at room temperature. Furthermore, the mechanism behind the superelasticity of Mg–Sc alloy has been systematically unveiled and the average rate of energy change per unit time of the alloys was calculated for the first time. Co doped Mg–Sc based alloys exhibited the lowest variations in the average rate of energy change per unit time, Helmholtz free energy, and M1, along with a higher charge density between Co and Sc atoms. Additionally, a coupling effect between the d orbital of Co and Sc electrons and a lowered Fermi level was observed. These findings demonstrate that Co doping in Mg–Sc based alloys significantly reduces the superelastic hysteresis area and transformation driving force, and increases Tm and strain, thereby enhancing superelasticity. This research guides further studies and the design of new Mg–Sc based lightweight SMAs with outstanding superelasticity at room temperature.

Synthesis and characterization of absorption-enhanced alumina solid particle materials for direct irradiation solar-thermal conversion

Based on solar-thermal application more than 1000 °C, a novel combination of sol-gel synthesis and stepwise calcination to prepare metal-ion doped alumina composite particles as heat transfer media were proposed, enhancing solar energy absorption and lowering preparation temperature. Investigations focused on the elemental distribution, phase composition, oxidation states, optical properties and thermal stability of the composites, which were doped with Cr, Co, Cu, Fe, and Mn metal ions in a 100:5 M ratio. The first-principles calculations elucidate the mechanism behind the impact of transition metal ions on alumina’s optical properties. Results show that introducing a small quantity of metal atoms results in new impurity energy levels and electron states around EF = 0. Specifically, the band gap energy of Cu- and Mn–Al2O3 decreases from 6.017 eV to 4.464 eV and 2.170 eV, respectively. Correspondingly, the absorptivity of these composite particles increases from around 20 %–76.6 %. And Tauc analysis indicates a decrease in the optical band gap of the particle materials from 5.37 eV to a range of 2.88–4.90 eV. Additionally, doping with Mn, Fe, and Cu accelerates the in-situ formation of α-Al2O3 crystals, with a phase transition temperature below 1000 °C and a crystallinity exceeding 93 %. Thermal stability tests show that the particles are highly stable, exhibiting a mere 0.49 % mass change between 30 °C and 1200 °C. The stepwise inert annealing strategy and metal-iron doping positively influence the optical performance of alumina, synthesizing long-term high-temperature stable alumina ceramic particles with absorptance enhancement and a low α-Al2O3 phase transition temperature. These attributes make a favorable choice for solar-thermal applications in direct irradiation.

Preparation of CMC-poly(N-isopropylacrylamide) semi-interpenetrating hydrogel with temperature-sensitivity for water retention

The CMC-PNIPAM hydrogel with semi-interpenetrating structure and temperature-sensitivity was prepared by in-situ polymerization of N-isopropylacrylamide (NIPAM) in sodium carboxymethylcellulose (CMC) solution at room temperature. The mass ratio of CMC to NIPAM was a key factor influencing the network structure and property of CMC-PNIPAM hydrogel. The low critical phase transition temperature (LCST) of CMC-PNIPAM hydrogels increased from 34.4 °C to 35.8 °C with the mass ratio of CMC to NIPAM rising from 0 to 1.2. The maximum compressive stress of CMC-PNIPAM hydrogel reached to 26.7 kPa and the relaxation elasticity was 52 % at strain of 60 %. The viscoelasticity of CMC-PNIPAM hydrogel was consistent with the generalized Maxwell model. The maximum swelling ratio in deionized water was 170.25 g·g−1 (dried hydrogel) with swelling rate of 2.57 g·g−1·min−1 at 25 °C. CMC-PNIPAM hydrogel hardly absorbed water above LCST, but the swollen hydrogel could release water at the rate of 0.36 g·g−1·min−1 once exceeding LCST. The test of water retention showed that soil mixed with 2 wt% dried CMC-PNIPAM hydrogel could retain 13.08 wt% water after 30 days at 25 °C that was 4.4 times than that of controlled soil without CMC-PNIPAM hydrogel. The semi-interpenetrating CMC-PNIPAM hydrogel showed a potential to conserve water responding to temperature.

Effects of Particle Size Distribution on the Physicochemical, Functional, and Structural Properties of Alfalfa Leaf Powder

To explore the effects of particle size distribution on its physicochemical, functional, and structural properties, alfalfa leaf powders with mean particle sizes (D50) of 506.1, 246.3, 209.8, 92.01, and 20.68 μm were prepared by sieving. The physicochemical, functional, and structural properties of alfalfa were compared, and correlation and principal component analyses were conducted. As the D50 of alfalfa leaf decreased, the bulk density, tap density, and the swelling capacity increased first and then decreased, but the compressibility, transition temperature, and melting temperature exhibited an opposite trend. The solubility, lightness, and inhibition of angiotensin-converting enzymes and tyrosinase were enhanced. Specifically, the alfalfa leaf with a D50 of 209.8 μm exhibited a higher bulk density and swelling capacity and a lower compressibility, transition temperature, and melting temperature. The alfalfa leaf with a D50 of 20.68 μm presented better solubility, lightness, and inhibition of angiotensin-converting enzymes and tyrosinase. Additionally, the surface roughness and the number of surface hydroxyls improved and the crystallinity index decreased, but the type of surface functional groups was unchanged. These changes in microstructure can provide an explanation for the trend of the physicochemical and functional properties. Moreover, based on the results of the correlation analysis and principal component analysis, it can be concluded that there are strong correlations among the particle size, physicochemical properties, and functional properties of alfalfa leaf. Overall, this conclusion can help determine the appropriate grinding particle size range for alfalfa leaf in different functional food products.

Shape Programmable and Multifunctional Soft Textile Muscles for Wearable and Soft Robotics

Textiles are promising candidates for use in soft robots and wearable devices due to their inherent compliance, high versatility, and skin comfort. Planar fluidic textile‐based actuators exhibit low profile and high conformability, and can seamlessly integrate additional components (e.g., soft sensors or variable stiffness structures [VSSs]) to create advanced, multifunctional smart textile actuators. In this article, a new class of programmable, fluidic soft textile muscles (STMs) that incorporate multilayered silicone sheets with embedded fluidic channels is introduced. The STMs are scalable and fabricated by apparel engineering techniques, offering a fabrication approach able to create large‐scaled multilayered structures that can be challenging for current microfluidic bonding methods. They are also highly automation compatible due to no manual insertion of elastic tubes/bladders into textile structures. Liquid metal is employed for creating fluidic channels. It is not only used for actuation but also used as channels for additional features such as soft piezoresistive sensors with enhanced sensitivity to STMs’ pressure‐induced elongation, or VSSs of either low‐melting‐point alloys or a new thermo‐responsive epoxy with low viscosity and transition temperature. The STMs hold promising prospects for soft robotic and wearable applications, which is demonstrated by an example of a textile‐based wearable 3D skin‐stretch haptic interface.

Two‐Photon Direct Laser Writing of pNIPAM Actuators in Microchannels for Dynamic Microfluidics

Microfluidic tools enable to investigate and manipulate various chemical and biological processes at small scales. As a result, it finds widespread applications in lab‐on‐chip devices, drug delivery systems, or miniaturized cell cultures. However, microfluidic devices are still limited in their flexibility and are often designed to fulfill a single functionality. Moreover, technologies to introduce dynamic functionalities with high precision and at high resolution after the development of a continuous phase microfluidic chip remain scarce. Herein, two‐photon polymerization direct laser writing is introduced as a suitable approach to equip continuous phase microfluidic chips with structurally defined thermoresponsive poly(N‐isopropyl‐acrylamide) (pNIPAM) microactuators. Harnessing the lower critical phase transition temperature of pNIPAM, and upon controlling specific design parameters, the efficient catch and release of polystyrene beads of different sizes using a pNIPAM micropillar brush array is demonstrated. Moreover, a biocompatible pNIPAM microgripper array is designed to subsequently capture and release differently sized (single) cell populations. Overall, the method offers great flexibility and a high degree of freedom toward the fabrication of dynamic microfluidic devices with great adaptability to experimental conditions in real time.

A Low Transition Temperature Mixture-based viscosupplementation complemented with celecoxib for osteoarthritis treatment

Viscosupplementation consists of hyaluronic acid (HA) intra-articular injections, commonly applied for osteoarthritis treatment while non-steroidal anti-inflammatory drugs (NSAIDs) are widely administered for pain relief. Here, HA and a NSAID (celecoxib) were combined in a formulation based on a low transition temperature mixture (LTTM) of glycerol:sorbitol, reported to increase celecoxib’s solubility, thus rendering a potential alternative viscosupplement envisioning enhanced therapeutic efficiency. The inclusion of glucosamine, a cartilage precursor, was also studied. The developed formulations were assessed in terms of rheological properties, crucial for viscosupplementation: the parameters of crossover frequency, storage (G’) and loss (G’’) moduli, zero-shear-rate viscosity, stable viscosity across temperatures, and shear thinning behaviour, support viscoelastic properties suitable for viscosupplementation. Additionally, the gels biocompatibility was confirmed in chondrogenic cells (ATDC5). Regarding drug release studies, high and low clearance scenarios demonstrated an increased celecoxib (CEX) release from the gel (6 to 73-fold), compared to dissolution in PBS. The low clearance setup presented the highest and most sustained CEX release, highlighting the importance of the gel structure in CEX delivery. NMR stability studies over time demonstrated the LTTM+HA+CEX (GHA+CEX) gel as viable candidate for further in vivo evaluation. In sum, the features of GHA+CEX support its potential use as alternative viscosupplement.