Soft Thermoplastic Polyurethane Research Articles

Porous flexible molecular-based piezoelectric composite achieves milliwatt output power density

Molecular ferroelectrics have made breakthrough progress in intrinsic piezoelectric response that can be on par with advanced inorganic piezoelectric ceramics. However, their successful applications in high-density energy harvesting and self-powered flexible devices have been great challenge, owing to the low elastic moduli, intrinsically brittle, and fracture proneness of such material systems under mechanical loading. Here, we have developed a flexible porous composite piezoelectric material by using soft thermoplastic polyurethane (TPU) and molecular ferroelectric materials. Benefiting from the porous structure of TPU, the flexible piezoelectric composites enable effectively large doping ratio (50%) of [Me3NCH2Cl]CdCl3 (TMCM-CdCl3) and highly efficient stress absorption, coupled with the excellent piezoelectric properties of TMCM-CdCl3, to realize a superior power density (636.9 µW cm−2 or 1273.9 µW cm−3). This output is 2000 times higher than that of flexible piezoelectric materials represented by poly(vinylidene fluoride) (PVDF). We believe that the outstanding performance of the porous composite piezoelectric material would pave a feasible way for real industrial applications of molecular ferroelectrics.

Decorative 3D printing on textiles using elastomer TPU filament under different printing conditions

PurposeNew sustainable approaches to fashion products are needed due to the demand for customization, better quality and cost reduction. Therefore, the decoration of fashion products using 3D printing technology can create a new direction for manufacturing science.Design/methodology/approachThis study aims to optimize the 3D printing of soft TPU material on textiles. In the past decade, trials of using 3D printing in tailored fashion products have been done due to the 3D printing simplicity, low cost of materials and time reduction. Therefore, soft polymers can be multi-layer stepped-deposited smoothly with the fused filament fabrication process.FindingsEven though there have been many attempts in the literature to 3D print multilayer polymer filaments directly onto textile fabrics by special-purpose 3D printers, only a few reports of decorative or personalized artefact 3D printing using open-platform filament material extrusion 3D printers. Printing speed, nozzle Z distance, textile fabric thickness and deposited strand height significantly affect 3D printing on textile fabric.Originality/valueThis study investigates the potential of 3D printing on textiles by changing the printing speed, nozzle hot end, Z distance and layer thickness. It presents two critical case studies of 3D printing soft thermoplastic polyurethane material on a cotton T-shirt and on a tulle textile to reveal the 3D printing on textile fabrics manufacturing challenges.

Silk-inspired architectured filament with enhanced stiffness and toughness for Fused deposition modelling (FDM)

Architectured materials, those capable of manipulating the spatial configurations of two or more material phases, have recently gained substantial attention, primarily due to their unprecedented material properties (e.g., exceptional strength-to-weight ratio and intriguing negative Poisson's ratio). Most architectured materials draw inspiration from the microstructure of natural solutions. One of fascinating examples are spider silk and cocoon silk. Their multimaterial core-shell fibrous structure exhibits remarkable mechanical properties—high stiffness, strength, and toughness. In this study, silk-inspired dual-phase Core-Shell Architectured Filament (CSAF), which combines a rigid Polylactic Acid (PLA) core with a soft Thermoplastic Polyurethane (TPU) shell, was developed as feedstock for additive manufacturing. The mechanical testing of dual-phase CASF printed samples reveal intriguing results. Notably, the optimized CASF in this study, whose volume fraction of rigid core was set as 52 %, was observed a substantial improvement of the printed specimens in initial stiffness and energy absorption capacity—up to a remarkable 14-fold increase in initial stiffness and a ∼9 % enhancement in energy absorption when compared to the pure TPU filament. To gain a deeper understanding of the synergistic effects arising from geometrical and material configurations on the structure's damage mechanism, a theoretical model of this core-shell structure was developed. Computational models have been built to validate theoretical model, and the results from finite element analysis are in excellent agreement with experimental results. These discoveries offer valuable insights to enhance mechanical performance of the feedstock for additive manufacturing.

Application of Multilayered Blend Films as Soft, Stretchable, Self‐Adhesive, and Self‐Healing Absorption‐Dominant EMI Shielding and Microwave Absorber

AbstractSolution‐processable organic conductor–supramolecular elastomer blends are emerging materials for intrinsically stretchable and autonomously self‐healing organic electronics. Herein, the feasibility of a heterogenous multiphase polymer blend is demonstrated for soft, ultraflexible, self‐adhesive, and self‐healing multilayered film structures for electromagnetic interference (EMI) shielding and microwave absorber (MWA) purposes. The developed soft multilayered films achieve a 5–40 fold improvement in the thickness of the MWA compared to the current state‐of‐the‐art. The thickness normalized reflection loss (RL) is up to 65.26 dB mm−1 with 8.5 GHz bandwidth at 18–26.5 GHz. The maximum thickness normalized EMI shielding effectiveness peaks at up to 175 dB mm−1. The EMI shielding and MWA properties are maintainable up to 150% tensile strain with only a small decrease in the overall attenuation and RL. Furthermore, the developed films are capable of fully autonomously self‐healing and achieve a tough adhesion in temperatures of −30–145 °C, and underwater with maximum single‐lap shear adhesion strength of ≈481.5 kPa to soft thermoplastic polyurethane films. Thus, the developed multilayered films can be utilized for absorption‐dominant EMI shielding or MWA purposes as stretchable coatings. The developed materials also show considerable potential for emerging damage and puncture‐resistant organic soft electronics with autonomous material‐level self‐healing.

Isolated and combined effects of EVA and TPU custom foot orthoses on constant speed, treadmill running kinematics

Introduction: We investigated the isolated and combined (HYB) effects of ethylene-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) custom foot orthoses (CFOs), compared to a control condition (CON; shoes only), on constant speed, treadmill running kinematics.Methods: Twenty (10 male and 10 female subjects) well-trained runners performed four 6-min bouts at the same individualized speed for each bout on a treadmill under four footwear conditions (EVA, TPU, HYB, and CON). Twenty markers and four clusters (four markers each) were placed on lower limbs and the pelvis. Lower limb and pelvis movements were tracked using a three-dimensional motion capture system with 11 cameras (Vicon MX System, Oxford, United Kingdom). Lower limb joint angles and angular velocity were normalized to 100% of the stance phase.Results: Peak ankle eversion (p < 0.001, η2 = 0.72), peak ankle eversion angular velocity (AV) (p < 0.001, η2 = 0.64), peak ankle inversion AV (p < 0.001, η2 = 0.60), and peak ankle internal rotation AV (p < 0.001, η2 = 0.49) demonstrated the largest differences between conditions. Statistical non-parametric mapping analysis revealed that HYB exhibited the largest proportions of change during the total stance phase compared to the CON.Discussion: All CFO materials caused significant reductions in peak angles and peak AVs at the ankle in the frontal plane, with more pronounced effects for harder (EVA) than softer (TPU) materials. These significant reductions occurred during large portions of the total stance phase for the angles and for the AVs. Although some effects could be found in more proximal joints such as the knee and hip, most significant effects were found at the ankle joint. Overall, combining hard EVA material in the heel and soft TPU in the forefoot (HYB) resulted in significant, more favorable changes compared to the CON that lasted for the largest proportion of stance phase when compared to wearing shoes only.

Whole Model Path Planning-Guided Multi-Axis and Multi-Material Printing of High-Performance Intestinal Implantable Stent.

The problems of step effects, supporting material waste, and conflict between flexibility and toughness for 3D printed intestinal fistula stents are not yet resolved. Herein, the fabrication of a support-free segmental stent with two types of thermoplastic polyurethane (TPU) using a homemade multi-axis and multi-material conformal printer guided with advanced whole model path planning is demonstrated. One type of TPU segment is soft to increase elasticity, and the other is used to achieve toughness. Owing to advancements in stent design and printing, the obtained stents present three unprecedented properties compared to previous three-axis printed stents: i) Overcoming step effects; ii) Presenting comparable axial flexibility to a stent made of a single soft TPU 87A material, thus increasing the feasibility of implantation; and iii) Showing equivalent radial toughness to a stent made of a single hard TPU 95A material. Hence, the stent can resist the intestinal contractive force and maintain intestinal continuity and patency. Through implanting such stents to the rabbit intestinal fistula models, therapeutic mechanisms of reducing fistula output and improving nutritional states and intestinal flora abundance are revealed. Overall, this study develops a creative and versatile method to improve the poor quality and mechanical properties of medical stents.

Stress concentration-relocating interposer in electronic textile packaging using thermoplastic elastic polyurethane film with via holes for bearing textile stretch

Electronic textile (e-textile) devices require mechanically reliable packaging that can bear up to 30% stretch induced by textile crimp stretch, because the boundary between the rigid electronic components and the soft fabric circuit in the e-textile is prone to rupture due to mismatch of their mechanical properties. Here, we describe a thin stress-concentration-relocating interposer that can sustain a textile stretch of up to 36%, which is greater than the 16% stretch of conventional packaging. The stress-concentration-relocating interposer consists of thin soft thermoplastic polyurethane film with soft via holes and is inserted between the electronic components and fabric circuit in order to move the area of stress concentration from the wiring area of the fabric circuit to the film. A finite element method (FEM) simulation showed that when the fabric is stretched by 30%, the boundary between the electrical components and the insulation layer is subjected to 90% strain and 2.5 MPa stress, whereas, at 30% strain, the boundary between the devices and the wiring is subjected to only 1.5 MPa stress, indicating that the concentration of stress in the wiring is reduced. Furthermore, it is shown that an optimal interposer structure that can bear a 30% stretch needs insulating polyurethane film in excess of 100 μm thick. Our thin soft interposer structure will enable LEDs and MEMS sensors to withstand stretching in several types of fabric.

Soft 3D printing of thermoplastic polyurethane: Preliminary study

Thermoplastic polyurethane (TPU) is a highly elastic linear polymer composed of soft segments, usually flexible polyester, or polyether. It is widely used in 3D printing technologies, being FFF the most common technique. However, stiffness and hardness values of 3D printed TPU in filament form are higher than would be desirable for some applications, which require softer parts. Therefore, it was seen necessary to find a new methodology for 3D printing soft TPU. In this way, the present study seeks to be the first research study that focuses on the possibility of 3D printing TPU using DIW (Direct Ink Writing) technology with UV light. Firstly, the optimal 3D printing and curing parameters to print soft TPU are determined and then two different TPU formulations are 3D printed. Then, both bulk and 3D printed TPU samples were characterized in terms of shear strength using the Warner-Bratzler shear test and hardness using the Shore hardness test. It was seen that the 3D printed samples showed higher softness than bulk samples compared to TPU filament. Finally, it was concluded that the 3D printing of TPU is challenging due to several points: (1) the viscosity of the TPU; (2) their main issue is their sticky behavior; and (3) the shrinkage which takes place after the thermal treatment and for some applications, it might be a problem. Despite that, TPU appears to be a promising material to be used in different industrial applications.

Design and fabrication of architected multi-material lattices with tunable stiffness, strength, and energy absorption

Modern engineering applications require advanced materials that are stronger, tougher, and lighter. Nature offers various structural architectures to achieve superior mechanical properties. Inspired by bone with a spongy soft-core and a compact hard-shell, this study introduces architected multi-material lattices with tunable mechanical properties such as stiffness, strength, and energy absorption. The architected lattices are fabricated via multi-material fused filament fabrication. The hard polylactic acid (PLA) shell of the lattice struts maintains the stiffness, while the soft thermoplastic polyurethane (TPU) core enhances toughness and energy absorption capacity. The microstructural and mixed-mode fracture characteristics of the PLA-TPU interfaces were examined since the interfacial microstructure and adhesion are crucial to stress transfer in multi-phase composite materials. This study explores the flexural behavior of the multi-material struts and reveals two distinct failure modes depending on the volume fraction of the soft-core through 3-point bend tests. This study demonstrates the bio-inspired design on a hexagonal planar lattice with a strut thickness-to-length ratio of 0.3. Tunable stiffness, strength, and energy absorption are achieved by varying the core-to-strut thickness ratio. Compression test results show that the architected lattices exhibit an energy absorption capacity that is about 2–3 times greater than that of the constituent single-phase lattices.

A multi-functional ammonia gas and strain sensor with 3D-printed thermoplastic polyurethane-polypyrrole composites

Fabrication methods for 3D soft and flexible gas/strain sensing materials are of great interest in various sensing fields. This study investigated electrically modifying 3D-printed soft thermoplastic polyurethane (TPU) as an ammonia gas/strain sensing material due to its tunable mechanical and stretchable properties and ease of fabrication. 3D-printed soft TPU were electrically modified with polypyrrole (PPy) using a sequential procedure of vapor phase polymerization (VPP). VPP can make two-phase composites with a high degree of homogeneity. PPy polymerized via VPP was distributed into a TPU matrix. Tunable mechanical properties were realized by changing the infill density (porosity) of 3D printed TPU. Moreover, TPU-PPy composites showed excellent electrical strain sensing behavior, stability, and durability during 5000 bending/releasing cycle loading. TPU-PPy composites were further evaluated for selectivity and sensitivity to investigate gas sensing behavior towards other reducing gases such as ammonia, triethylamine, ethanol, and methanol. 3D-printed and electrically modified soft TPU showed great potential as an ammonia gas sensor and as a strain sensing material with high performance.

Effect of the Segmental Structure of Thermoplastic Polyurethane (Hardness) on the Interfacial Adhesion of Textile-Grade Carbon Fiber Composites

In polymer composites, the fiber–matrix interface is primarily influenced by the surface treatment of the fibers and polymer morphology. Previous studies have investigated the effect of surface treatment of carbon fiber on the mechanical properties of the resulting composites. However, very few studies have explored the chemical structural modification of polymer effect on the fiber–matrix adhesion. In this work, the interfaces of soft thermoplastic polyurethane (S-TPU) and hard-segmented TPU (H-TPU) were investigated through surface, thermal, and mechanical characterization. A textile-grade carbon fiber (TCF) with 1% concentration of epoxy sizing (an emerging material for nonaerospace applications with 450 K filament tows) was used as a reinforcement to investigate the structure–property relationship at the interface. Atomic force microscopy results showed 39% higher surface roughness for S-TPU than for H-TPU. X-ray photoelectron spectroscopy results revealed a 550% increase in C═O content, which can provide multiple hydrogen bonding networks in H-TPU, and these C═O bonds can produce a strong chemical bond at the fiber–matrix interface. Dynamic mechanical analysis and differential scanning calorimetry results confirmed the presence of hydrogen bonding that enhances the cross-linked density by 232% in H-TPU compared to S-TPU. The improved mechanical properties of H-TPU composites, such as flexural, impact and tensile by 30, 50, and 130% compared to S-TPU composites, prove that the crystallinity and hydrogen bonding significantly increase the load bearing capacity due to the strong interface. The mechanical properties of TCF–TPU composites validate the formation of chemical bonds through a nucleophilic addition reaction at the interface and improve the bond strength of the composites. Thus, tailoring the polyurethane structure broadens the performance of segmented TPU in conjunction with TCF reinforcement, which has implications for cost-effective, high-strength composites.

Preparation of Microcellular Foams by Supercritical Carbon Dioxide: A Case Study of Thermoplastic Polyurethane 70A

In this study, a case study to produce microcellular foam of a commercial thermoplastic polyurethane (TPU) through the supercritical carbon dioxide (CO2) foaming process is presented. To explore the feasibility of TPU in medical device and biomedical application, a soft TPU with Shore hardness value of 70A was selected as the model compound. The effects of saturation temperature and saturation pressure ranging from 90 to 140 °C and 90 to 110 bar on the expansion ratio, cell size and cell density of the TPU foam were compared and discussed. Regarding the expansion ratio, the effect of saturation temperature was considerable and an intermediate saturation temperature of 100 °C was favorable to produce TPU microcellular foam with a high expansion ratio. On the other hand, the mean pore size and cell density of TPU foam can be efficiently manipulated by adjusting the saturation pressure. A high saturation pressure was beneficial to obtain TPU foam with small mean pore size and high cell density. This case study shows that the expansion ratio of TPU microcellular foam could be designed as high as 4.4. The cell size and cell density could be controlled within 12–40 μm and 5.0 × 107–1.3 × 109 cells/cm3, respectively.

Antishrinking Strategy of Microcellular Thermoplastic Polyurethane by Comprehensive Modeling Analysis

A comprehensive model for shrinkage behavior of soft thermoplastic polyurethane (TPU) elastomer foams has been built, which involves in situ tensile testing of TPU under different carbon dioxide (CO₂) plasticization pressures and antishrinking abilities of different cell shapes of circular, square, and hexagonal evaluated by a three-order Ogden hyperelastic equation. Combined with the nitrogen (N₂)-assisted supercritical carbon dioxide CO₂ foaming and aging experimental results, it was found that the hexagonal cells can match the actual shrinkage process well, and no less than 50% N₂ content remaining in cells can effectively improve the antishrinking ability of TPU foams. According to the principle that there is no pressure difference between inside and outside foam, a feasible method of aging TPU foam under a variable ambient vacuum to reduce the shrinkage ratio was proposed, simulated, and proved.

Thermoplastic Blend Exhibiting Shape Memory-Assisted Self-Healing Functionality

Here, we report on a polymer blend consisting of a soft thermoplastic polyurethane (TPU) elastomer and a low melting temperature thermoplastic healing agent (polycaprolactone, PCL). In this study, polymer blends containing up to 60 wt % PCL were prepared and the resulting mechanical, thermal, shape memory, and self-healing properties were studied. These immiscible polymers exhibit two well-separated transitions attributable to the melting of PCL and TPU hard segments. This viscoelastic behavior engendered shape memory capability at moderate processing temperatures (∼90 °C) and melt processability at elevated temperatures (>160 °C). The reversible plasticity shape memory (RPSM) effect was also characterized: when subjected to 125% strain at room temperature and subsequently heated to 90 °C, the samples nearly fully recovered to their original length. Moreover, upon heating to above PCL's melting temperature, the flow of PCL into an undeformed crack was shown to fill the crack void, thus promoting self-repair. Through the action of mild heating (90 °C/30 min), fracture surfaces are brought into intimate contact through the action of the RPSM effect and subsequently healed through the redistribution of molten PCL. The shape memory-assisted self-healing efficiency was evaluated by comparing the tensile force restoration after healing of a highly deformed, notched sample to its behavior prior to notching. It was observed that blends containing up to 30 wt % PCL showed nearly complete restoration of properties. In contrast, pure TPU showed only about 5% healing efficiency because of the absence of the PCL healing agent. Blends containing 50 and 60 wt % PCL likewise did not exhibit appreciable restoration of properties, and this was attributed to their propensity to neck during crack opening and poor mechanical properties at elevated temperatures. Blends may serve as a self-healing replacement for pure TPU in existing applications (e.g., automotive and sporting goods) or as a self-healing shape memory polymer in advanced products in soft robotic, biomedical, and microelectronic applications.

Additive Manufacturing With Soft TPU – Adhesion Strength in Multimaterial Flexible Joints

The adhesion in 3D-printed composites between dissimilar layers was investigated in response to demand for multimaterial prints. Previously, we reported on the thermal properties for printability of thermoplastic polyurethane (TPU) blends~\cite{harris001}. Here, we report the qualitative and quantitative adhesion properties between commonly-printed materials, acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA), and flexible TPU. ASTM D1002/D3164 lap shear adhesion tests were performed to measure the adhesion strength between the acrylonitrile plastics and TPU, finding values of $4.7~\mathrm{MPa}$ between ABS and TPU and $6.4~\mathrm{MPa}$ between ASA and TPU. These values are on the same order of magnitude of reported commercial adhesives, suggesting that multimaterial 3D printing can provide an automated, industrially-relevant alternative to handmade fabrication. SEM images are reported to show the quality of adhesion between materials in the composites. These images expose qualitative differences in the interlayer adhesion between materials in the composites that depend on the \textit{order of printing}. Thermal (DSC and TGA) and rheological characterizations were performed to investigate the processing conditions of the extruded plastics while they are in their melt states. The role of viscosity is shown to have major implications on the adhesion, as materials with lower viscosities displayed improved filling of the interlayer voids and increased strength of adhesion.

Nanocomposite foams based on flexible biobased thermoplastic polyurethane and ZnO nanoparticles as potential wound dressing materials

In the present study biobased and soft thermoplastic polyurethane (TPU), obtained by polymerization from fatty acids, was used to produce TPU/ZnO nanocomposite foams by thermally induced phase separation method (TIPS). The produced foams were characterized and evaluated regarding their potential uses as wound dressing materials. The structure and morphology of the prepared flexible polymer foams with different content of ZnO nanofiller (1, 2, 5 and 10 wt% related to the polymer) were studied by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Highly porous nanocomposite structure made of interconnected pores with dimensions between 10 and 60 μm was created allowing water vapor transmission rate (WVTR) up to 8.9 mg/cm2·h. The TPU/ZnO foams, tested for their ability to support cells and their growth, showed highest cell proliferation for TPU nanocomposite foams with 2 and 5 wt% ZnO. Overall, the nanocomposite foams displayed a low cytotoxic potential (varied proportionally to the ZnO content) and good biocompatibility. All tested nanocomposite foams were found to be significantly active against biofilms formed by different Gram-positive (Enterococcus faecalis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. Based on their behaviors, flexible TPU/ZnO nanocomposite foams can be considered for biomedical applications such as potential active wound dressing.

Porosity and tissue integration of elastic mesh implants evaluated in vitro and in vivo.

In vivo, a loss of mesh porosity triggers scar tissue formation and restricts functionality. The purpose of this study was to evaluate the properties and configuration changes as mesh deformation and mesh shrinkage of a soft mesh implant compared with a conventional stiff mesh implant in vitro and in a porcine model. Tensile tests and digital image correlation were used to determine the textile porosity for both mesh types in vitro. A group of three pigs each were treated with magnetic resonance imaging (MRI) visible conventional stiff polyvinylidene fluoride meshes (PVDF) or with soft thermoplastic polyurethane meshes (TPU) (FEG Textiltechnik mbH, Aachen, Germany), respectively. MRI was performed with a pneumoperitoneum at a pressure of 0 and 15 mmHg, which resulted in bulging of the abdomen. The mesh-induced signal voids were semiautomatically segmented and the mesh areas were determined. With the deformations assessed in both mesh types at both pressure conditions, the porosity change of the meshes after 8 weeks of ingrowth was calculated as an indicator of preserved elastic properties. The explanted specimens were examined histologically for the maturity of the scar (collagen I/III ratio). In TPU, the in vitro porosity increased constantly, in PVDF, a loss of porosity was observed under mild stresses. In vivo, the mean mesh areas of TPU were 206.8 cm2 (± 5.7 cm2 ) at 0 mmHg pneumoperitoneum and 274.6 cm2 (± 5.2 cm2 ) at 15 mmHg; for PVDF the mean areas were 205.5 cm2 (± 8.8 cm2 ) and 221.5 cm2 (± 11.8 cm2 ), respectively. The pneumoperitoneum-induced pressure increase resulted in a calculated porosity increase of 8.4% for TPU and of 1.2% for PVDF. The mean collagen I/III ratio was 8.7 (± 0.5) for TPU and 4.7 (± 0.7) for PVDF. The elastic properties of TPU mesh implants result in improved tissue integration compared to conventional PVDF meshes, and they adapt more efficiently to the abdominal wall. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 827-833, 2018.

Microconfinement effect on gas barrier and mechanical properties of multilayer rigid/soft thermoplastic polyurethane films

ABSTRACTIn this article, rigid/soft thermoplastic polyurethane (TPU) films were produced via layer‐multiplying co‐extrusion and the effect of confinement on morphology and gas barrier and mechanical properties is studied. The soft TPU, which is 52% hard‐segment, shows phase separation, while the rigid, 100% hard‐segment TPU exhibits amorphous structures. Even though the viscosity ratio of the two TPUs is over 10 and the elasticity ratio around 100, optical and atomic force microscopies show that a multilayer structure was successfully achieved. Then, the multilayer TPU films were uni‐axially stretched to different amounts of deformations, from 0% to 300%. DSC and WAXS results show that microconfinement occurs during orientation, which causes a significant reduction in oxygen permeability of multilayer TPU films, when stretched at 75%, by comparison to the mono and bi‐layer TPU. The dependence of gas barrier properties on temperature and deformation was also investigated, and a 100% improvement in elongation at break was found when compared to films of the rigid TPU. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41849.

Properties and fibroblast cellular response of soft and hard thermoplastic polyurethane electrospun nanofibrous scaffolds.

Soft and hard thermoplastic polyurethane (TPU) and their blends were electrospun to fabricate nanofibrous scaffolds with various properties in order to investigate the substrate property effects on cellular response. The scaffolds were characterized with Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, water contact angle tests, and protein absorption tests. It was found that the hard segment content in the scaffold increased with the hard TPU ratio, which resulted in improved hydrophobicity and decreased over all protein absorption. 3T3 fibroblasts were cultured on those scaffolds to investigate the cellular response. On soft TPU scaffolds, the cells formed were round in shape and aggregated into clusters. However, on hard TPU scaffolds, the cells exhibited a spindle shape and spread out on the scaffolds, indicating preferred cell-substrate interaction. The cell viability and proliferation of cells on hard scaffolds were higher than on soft scaffolds and on 50% hard/50% soft scaffolds.

Thermoplastic polyurethane/hydroxyapatite electrospun scaffolds for bone tissue engineering: Effects of polymer properties and particle size

Thermoplastic polyurethane (TPU)/hydroxyapatite (HA) scaffolds were fabricated via electrospinning. The effects of TPU properties and HA particle size on scaffold physical properties and osteoblast-like cell performance were investigated. It was found that the addition of micro-HA (mHA), which was inlayed in the fiber, decreased the electrospun fiber diameter. On the contrary, nano-HA (nHA), which was either embedded or existed inside of the fiber, increased the fiber diameter for both soft and hard TPUs. The soft TPU had a much lower Young's modulus and higher strain-at-break than the hard TPU. The addition of both mHA and nHA decreased the tensile properties; this decrease was more significant with mHA. The cells on the hard scaffolds actively proliferated and migrated compared to those on the soft scaffolds. On the other hand, cells on the soft scaffolds more effectively induced osteogenesis of human mesenchymal stem cells (hMSCs) than those on the hard scaffolds. In addition, our data suggest that the soft scaffolds with supplementation of nHA further enhanced osteogenesis of hMSCs compared to those without nHA. The soft TPU scaffolds containing nano-HA have the potential to be used in bone tissue engineering applications.