Anton Paar Physica

Due to its hydroxyl terminal groups, Poloxamer^® 407 (P407), a commercially available poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer can be used as macrodiol for the synthesis of high molecular weight amphiphilic poly(ether urethane)s (PEUs). This work was aimed at studying the effect of P407 purification by removing PEO-PPO diblock copolymer by-products on the chemical properties of PEU polymer and the physical properties of PEU hydrogels. Removal of PEO-PPO diblock copolymers (P407_P) was found to preserve the thermo-responsiveness of resulting hydrogels, although slightly lower gelation onset temperature (T_onset) was found for P407_P (15.3°C) vs. P407 (16.7°C) hydrogels (25% w/V) as assessed through temperature ramp test. P407 and P407_P were then reacted with 1,6-diisocyanatohexane and 1,4-cyclohexanedimethanol to synthesize two different PEUs, coded as CHP407 and CHP407_P, respectively. Lower Number Average Molecular Weight () and higher polydispersity Index (D) was measured for CHP407 (: 34 kDa, D: 1.6) respect to CHP407_P (: 40 kDa, D: 1.4) as a consequence of macrodiol purification. CHP407_P hydrogels formed bigger micelles (43.9 ± 4.1 nm vs. 28.7 ± 4 nm) while showed similar critical micellar temperatures (22.1°C vs. 21.6°C) respect to CHP407 formulations. Sol-to-gel transition of CHP407 and CHP407_P hydrogels was similar while CHP407_P gelation time at 37°C was longer as assessed by tube inverting test. The rheological analysis showed slightly lower T_onset for CHP407_P hydrogels (15% w/V), probably due to larger micelle size, promoting micellar assembly. However, CHP407_P hydrogels showed a significantly lower critical strain than CHP407 hydrogels, as assessed by strain sweep test, suggesting their higher brittleness due to a lower density of intermicellar bridge chains. Nano-scale hydrogel characterization by Low-Field Nuclear Magnetic Resonance spectroscopy supported previous findings, showing lower spin-spin relaxation time (i.e., 1,259 ms) for CHP407_P than for CHP407 hydrogels (i.e., 1,560 ms) at 37°C, which suggested the formation of a more tightly packed network for CHP407_P than CHP407 hydrogel. Finally, lower swelling capability and resistance against dissolution were measured for CHP407_P hydrogels. Overall, the here‐reported results suggested that the heterogeneous structure in the CHP407 hydrogel network caused by the presence of diblock copolymer-based macrodiols improved PEU hydrogel properties in light of their applicability in the biomedical field.

Rossella Laurano, Michela Abrami, Mario Grassi, Gianluca Ciardelli, Monica Boffito, Valeria Chiono. Frontiers in Materials, 7, 2020.

In this article, a magnetorheological shear thickening fluid (MRSTF) was fabricated based on magnetorheological (MR) material and shear thickening fluid (STF). The STF was firstly fabricated as the liquid phase, and carbonyl iron particles were then mixed with the prefabricated STF to synthesise a series of MRSTFs with various iron concentrations. Then, a rheometer was used to measure their viscosities by varying the shear rate under various magnetic fields. Both static and dynamic tests were conducted to study the rheology of MRSTFs under different magnetic fields. The tested results revealed that the MRSTF showed shear thickening under zero magnetic field and MR effect with increasing applied magnetic field. It was also noted that the viscosity of the MRSTFs can be controlled by both shear rate and the applied magnetic field. The concentration of iron particles played an important role in the MRSTFs’ rheological properties. The MRSTFs with higher iron particle concentrations revealed lower shear thickening effects but higher MR effects, which means the MRSTF with higher iron concentration can be treated as an effective MR fluid. Meanwhile, the MRSTF with low iron concentration displays good shear thickening effect under weak magnetic field. To summarise the behavior of MRSTFs with various iron concentrations and under different magnetic fields, three regions were proposed to provide guidelines to design MRSTFs and assist in their applications.

Vladimir Sokolovski, Tongfei Tian, Jie Ding, Weihua Li. Frontiers in Materials, 7, 2020.

The application of magneto-sensitive (MS) rubber in a vehicle vibration control area is likely to be expected. This conclusion is based on the following two reasons: the maturity of fabrication of MS rubber which meets the application requirement and the feasibility of the constitutive model of MS rubber that accurately reflects its mechanical performance. Compared with the traditional rubber, small ferromagnetic particles are embedded in the elastomer of MS rubber, leading to a change of mechanical properties when an external magnetic field is applied. Therefore, devices with MS rubber, can be viewed as a semi-active actuator. In this study, MS rubber with a relative high increase in the magneto-induced modulus is fabricated and characterized. Furthermore, a one-dimensional constitutive model to depict the magnetic field-, frequency-, and strain amplitude-dependent dynamic modulus of MS rubber is applied. Finally, simulations of a MS rubber semi-active suspension under a bump and a random ground excitation with different control strategies on a quarter vehicle model are conducted to illustrate the feasibility of the MS rubber in the vehicle vibration control application context.

Bochao Wang, Tao Hu, Longjiang Shen, Jun Li, Zhenbang Xu, Leif Kari, Xinglong Gong. Frontiers in Materials, 8, 2021.

The interface between the particles and the carrier fluids has an important influence on the performance of magnetorheological fluid (MRF). In this study, ionic liquids and silicone oils with the same viscosity and different surface tensions were used as carrier fluids to prepare two different carbonyl iron powder (CIP) magnetorheological fluids. The rheological properties of the two magnetorheological fluids were evaluated by the MCR301 rotating rheometer. The experimental results indicate that ionic liquid-based MRF showed higher shear yield strength and more significant MR effect than silicone oil-based ones in higher magnetic field strength. A possible explanation was proposed and proved through experimental data analysis.

Yu Tong, Xiaoguang Li, Penghui Zhao, Xufeng Dong, Zhanjun Wu, Min Qi. Frontiers in Materials, 8, 2021.

This article studies the creep and recovery behavior of magnetorheological grease (MRG) under constant stress shear. The experiment is done by using a parallel plate rheometer with magnetron attachment and temperature control unit. The effects of constant stress, CI particle concentration, magnetic flux density and temperature on creep and recovery behavior are systematically studied. Experimental results show that as the constant stress increases, the response strain will also increase. The creep strain tested under zero field is higher than the value tested under a magnetic field, indicating that the creep and recovery behavior of MRG is highly dependent on the magnetic field strength. In addition, the creep and recovery behavior of MRG is greatly affected by temperature. Under the action of a magnetic flux density, the creep strain will decrease with the increase of temperature. The result is opposite at zero magnetic field.

Xudan Ye, Jiong Wang. Frontiers in Materials, 8, 2021.

Not-from-concentrate (NFC) juice is popular with consumers due to its similarity to fresh fruit juice in taste, flavor, and beneficial nutrients. As a commonly used technology in fruit juice production, high-pressure homogenization (HPH) can enhance the commercial value of juice by improving the color, flavor, taste, and nutrient contents. In this study, the effects of HPH on the pectin structural properties and stability of NFC orange juice were investigated. The correlations between HPH-induced changes in the structure of pectin and the stability of orange juice were revealed. Compared with non-homogenized orange juice, HPH increased the galacturonic acid (GalA) content and the linearity of pectin, while decreasing the molecular weight (Mw), pectin branching, and rhamnogalacturonan (RG) contribution, and cracks and pores of different sizes formed on the surface of pectin, implying depolymerization. Meanwhile, with increasing pressure and number homogenization of passes, HPH effectively improved the stability of NFC orange juice. HPH can effectively prevent the stratification of orange juice, thereby promoting consumer acceptance and endowing a higher commercial value. The improvement of the stability of NFC orange juice by HPH was related to the structural properties of pectin. Turbidity was significantly (P < 0.01) positively correlated with GalA and pectin linearity, but was significantly (P < 0.01) negatively correlated with Mw, RG contribution, and pectin branching. Modification of pectin structure can improve the stability of NFC orange juice. In this work, the relationship between the pectin structure and stability of NFC orange juice is elucidated, providing a path toward improving consumer acceptance and enhancing the palatability and nutritional and functional qualities of orange juice. Manufacturers can use this relationship to modify pectin directionally and produce high-quality NFC orange juice beverages.

Wantong Yu, Jiefen Cui, Shaojie Zhao, Liping Feng, Yanqi Wang, Junmei Liu, Jinkai Zheng. Frontiers in Nutrition, 8, 2021.

Cobalt particles have been introduced as a filler due to the advantages of embedding their magnetic and electrical properties in magnetorheological elastomer (MRE). In the present research, the rheology and resistance of MRE are experimentally evaluated. Isotropic and anisotropic MRE samples containing silicone rubber and cobalt particles were fabricated. The magnetic properties of MRE are conducted using a vibrating sample magnetometer (VSM). The morphological aspects of MRE are observed by using field emission scanning electron microscopy (FESEM) and characterized by energy-dispersive X-ray spectroscopy (EDX). Rheological properties under various magnetic field strengths were measured for the magnetic field, strain amplitude, and frequency sweep test by using a parallel-plate rheometer. Subsequently, the resistance of MRE is tested under different applied forces and magnetic fields. The MRE storage modulus depicted an enhancement in field-dependent modulus across all the applied magnetic fields. The electrical resistance generated from the sample can be manipulated by external magnetic fields and mechanical loads. The conductivity of MRE is due to the existence of cobalt arrangements observed by FESEM. By introducing cobalt as filler and obtaining satisfactory results, the study might open new avenues for cobalt to be used as filler in MRE fabrication for future sensing applications.

Afiq Azri Zainudin, Nurul Azhani Yunus, Saiful Amri Mazlan, Muhammad Kashfi Shabdin, Siti Aishah Abdul Aziz, Nur Azmah Nordin, Nurhazimah Nazmi, Mohd Azizi Abdul Rahman. Applied Sciences, 10 (5), 1638, 2020.

The study described in this paper focused on the possible use of waste products coming from the production of styrene–butadiene rubber (SBR) and polybutadiene rubber (PBR), as bitumen modifiers. Modified binders containing these products were prepared in the laboratory with different polymer dosages and were thereafter subjected to the evaluation of empirical and rheological properties. For comparative purposes, the study also considered SBR and PBR products of premium quality. Ageing effects were also taken into account by means of proper laboratory simulations. Obtained results indicated that the two types of polymer (SBR and PBR) have completely different effects on the rheology and expected performance of the resulting modified binders. In particular, while the two polymers showed similar effects in terms of resistance to permanent deformation, the SBR products proved to be superior from the viewpoint of fatigue resistance. However, only minor differences were found when comparing the effects produced by premium quality and waste polymers. As a result of the experimental findings, it was concluded that the use of waste SBR polymers can be an attractive solution for the production of affordable modified binders.

Sadegh Yeganeh, Mahmoud Ameri, Davide Dalmazzo, Ezio Santagata. Applied Sciences, 10 (8), 2671, 2020.

This study presents measured density and viscosity of N-methyldiethanolamine (MDEA) + H2O, Dimethylethanolamine (DMEA) + H2O, and Diethylethanolamine (DEEA) + H2O mixtures. The density was measured at amine mass fraction w1 from 0.3 to 1 for the temperature range 293.15–353.15 K. The excess molar volumes VE were determined from density data. Redlich–Kister type polynomials were proposed to fit VE and density deviation ln(ργ) to represent measured densities. The viscosity was measured at amine mass fraction w1 from 0.3 to 1 for the temperature range 293.15–363.15 K. The viscosity deviation ηE and excess free energy of activation for viscous flow ΔGE* were determined from measured viscosities and examined for intermolecular interactions among mixture molecules. Correlations were proposed to fit viscosity data with acceptable accuracies. The McAllister’s three-body model was adopted to fit kinematic viscosities determined from density and dynamic viscosity data. The results showed the importance of examining intermolecular interactions that are discussed in McAllister’s four-body model to improve the accuracies of data fits.

Sumudu S. Karunarathne, Dag A. Eimer, Lars E. Øi. Applied Sciences, 10 (9), 3196, 2020.

Bone tissue engineering provides advanced solutions to overcome the limitations of currently used therapies for bone reconstruction. Dynamic culturing of cell-biomaterial constructs positively affects the cell proliferation and differentiation. In this study, we present a precisely flow-controlled microfluidic system employed for the investigation of bone-forming cell responses cultured on fibrous collagen matrices by applying two flow rates, 30 and 50 μL/min. We characterized the collagen substrates morphologically by means of scanning electron microscopy, investigated their viscoelastic properties, and evaluated the orientation, proliferation and osteogenic differentiation capacity of pre-osteoblastic cells cultured on them. The cells are oriented along the direction of the flow at both rates, in contrast to a random orientation observed under static culture conditions. The proliferation of cells after 7 days in culture was increased at both flow rates, with the flow rate of 50 μL/min indicating a significant increase compared to the static culture. The alkaline phosphatase activity after 7 days increased at both flow rates, with the rate of 30 μL/min indicating a significant enhancement compared to static conditions. Our results demonstrate that precisely flow-controlled microfluidic cell culture provides tunable control of the cell microenvironment that directs cellular activities involved in bone regeneration.

Eleftheria Babaliari, George Petekidis, Maria Chatzinikolaidou. Bioengineering, 5 (3), 66, 2018.

Fibrosis of burn-related wounds remains an unresolved clinical issue that leads to patient disability. The aim of this study was to assess the efficacy of the transplantation of adipose-derived stromal cells seeded onto a collagen-based matrix in the reconstruction of burn-related scars. Here, we characterized an in vitro interaction between adipose-derived stromal cells and a collagen-based matrix, Integra®DRT. Our results show that transcription of pro-angiogenic, remodeling, and immunomodulatory factors was more significant in adipose-derived stromal cells than in fibroblasts. Transcription of metalloproteinases 2 and 9 is positively correlated with the collagenolytic activity of the adipose-derived stromal cells seeded onto Integra®DRT. The increase in the enzymatic activity corresponds to the decrease in the elasticity of the whole construct. Finally, we validated the treatment of a post-excision wound using adipose-derived stromal cells and an Integra®DRT construct in a 25-year-old woman suffering from burn-related scars. Scarless healing was observed in the area treated by adipose-derived stromal cells and the Integra®DRT construct but not in the reference area where Integra®DRT was applied without cells. This clinical observation may be explained by in vitro findings: Enhanced transcription of the vascular endothelial growth factor as well as remodeling of the collagen-based matrix decreased mechanical stress. Our experimental treatment demonstrated that the adipose-derived stromal cells seeded onto Integra®DRT exhibit valuable properties that may improve post-excision wound healing and facilitate skin regeneration without scars.

Marcin Piejko, Karolina Radziun, Sylwia Bobis-Wozowicz, Agnieszka Waligórska, Eliza Zimoląg, Michał Nessler, Anna Chrapusta, Zbigniew Madeja, Justyna Drukała. Bioengineering, 7 (3), 67, 2020.

Layer-by-layer additive manufacturing process has evolved into three-dimensional (3D) “bio-printing” as a means of constructing cell-laden functional tissue equivalents. The process typically involves the mixing of cells of interest with an appropriate hydrogel, termed as “bioink”, followed by printing and tissue maturation. An ideal bioink should have adequate mechanical, rheological, and biological features of the target tissues. However, native extracellular matrix (ECM) is made of an intricate milieu of soluble and non-soluble extracellular factors, and mimicking such a composition is challenging. To this end, here we report the formulation of a multi-component bioink composed of gelatin and alginate -based scaffolding material, as well as a platelet-rich plasma (PRP) suspension, which mimics the insoluble and soluble factors of native ECM respectively. Briefly, sodium alginate was subjected to controlled oxidation to yield alginate dialdehyde (ADA), and was mixed with gelatin and PRP in various volume ratios in the presence of borax. The formulation was systematically characterized for its gelation time, swelling, and water uptake, as well as its morphological, chemical, and rheological properties; furthermore, blood- and cytocompatibility were assessed as per ISO 10993 (International Organization for Standardization). Printability, shape fidelity, and cell-laden printing was evaluated using the RegenHU 3D Discovery bioprinter. The results indicated the successful development of ADA–gelatin–PRP based bioink for 3D bioprinting and biofabrication applications.

Lakshmi T. Somasekharan, Naresh Kasoju, Riya Raju, Anugya Bhatt. Bioengineering, 7 (3), 108, 2020.

The rheopectic behavior of sacran aqueous solutions, a natural giant molecular polysaccharide with a molecular weight of 1.6 × 107 g/mol, was investigated. When a low shear was applied to 1.0 wt.% sacran solution, the shear viscosity increased from 7.2 to 34 Pa·s. The increment in the viscosity was enhanced as the shear rate decreased. The shear viscosity was independent of the time at a shear rate of 0.8 s−1; simultaneously, thixotropic behavior was observed at shear rates higher than 1.0 s−1. A crossover was observed at 0.15 wt.% for the concentration dependence of both the viscosity increase and zeta potential, which was the vicinity of the helix transition concentration or gelation concentration. It was clear that the molecular mechanism for the rheopexy was different at lower and higher regions of the crossover concentration.

Fitri Amat Yusof, Miho Yamaki, Mika Kawai, Maiko Okajima, Tatsuo Kaneko, Tetsu Mitsumata. Biomolecules, 10 (1), 155, 2020.