Strain sensors play a pivotal role in quantifying stress and strain across diverse domains, encompassing engineering, industry, and medicine. Their applicability has recently extended into the realm of wearable electronics, enabling real-time monitoring of body movements. However, conventional strain sensors, while extensively employed, grapple with limitations such as diminished sensitivity, suboptimal tensile strength, and susceptibility to environmental factors. In contrast, polymer-based composite strain sensors have gained prominence for their capability to surmount these challenges. The integration of carbon nanotubes (CNTs) as reinforcing agents within the polymer matrix ushers in a transformative era, bolstering mechanical strength, electrical conductivity, and thermal stability. This study comprises three primary components: simulation, synthesis of nanocomposites for strain sensor fabrication, and preparation of a comprehensive measurement set for testing purposes. The fabricated strain sensors, incorporating a robust polymer matrix of polyaniline known for its exceptional conductivity and reinforced with carbon nanotubes as strengthening agents, demonstrate good characteristics, including a high gauge factor, stability, and low hysteresis. Moreover, they exhibit high strain sensitivity and show linearity in resistance changes concerning applied strain. Comparative analysis reveals that the resulting gauge factors for composite strain sensors consisting of carbon nanotubes/polyaniline and carbon nanotubes/polyaniline/silicone rubber are 144.5 and 167.94, respectively.

In this study, we produced electrospun scaffolds from 10% pure PLGA solution, and 10% polyblend solutions of PLGA/Fibrin, PLGA/Lignin, and PLGA/Fibrin/Lignin with proportions of 9:1, 8:2, 7:3, 7:2:1, 6:2:2, and 5:2:3 and characterized them physiochemically and biologically. FTIR and EDX results verified the chemical composition of the fibers. All scaffolds exhibited homogenous nanostructures with fiber diameters ranging from 0.1 to 2.5 μm and the highest average fiber diameter belonged to PLGA/Lignin fibers. Increasing the lignin proportion led to a decrease in fibers diameter and a change in color to brown. Fibrin improved the hydrophobicity of the scaffolds, and the incorporation of fibrin, lignin, or fibrin/lignin improved the absorption capacity of the scaffolds (up to 91.7%). From day 45 onwards, fibrin-containing scaffolds started to degrade much faster. By day 90, PLGA/20%Fibrin/30%Lignin showed the highest degradation ratio of 82%, while PLGA/10%Lignin showed the lowest at 51.4%. All scaffolds exhibited high porosity percentage (over 78%), with porosity enhanced by increasing fibrin and decreasing lignin. The pure PLGA scaffold and PLGA/10%Lignin showed the highest stiffness and tensile strength, respectively. The addition of natural components gradually decreased the scaffolds’ tensile strength and fracture strain. MTT results showed higher absorbance reading at 490 nm for PLGA, PLGA/10%Fibrin, and all three PLGA/Lignin scaffolds from day 3 to day 7. On day 7, PLGA/10%Fibrin exhibited the highest cell viability, followed by PLGA/10%Lignin and PLGA/20%Fibrin/10%Lignin. SEM micrographs revealed the presence of h-ADSCs with spindle-like morphologies, attached and proliferated well on all scaffolds. PLGA/10%Fibrin, PLGA/10%Lignin, and PLGA/20%Fibrin/10%Lignin were selected as the preferred options from each set of scaffolds. Among them, PLGA/20%Fibrin/10%Lignin exhibited superior physical features and actively enhanced the biological responses of the cells due to its physio-mechanical signals and the advanced features of lignin, making it suitable for tissue engineering, wound dressing, drug delivery, and other biomedical applications.

Introduction: A synthetic biomaterial, such as poly(lactic-co-glycolic acid) (PLGA) with superior mechanical properties, along with a natural polymer such as fibrin, which facilitates cell attachment and enhances biocompatibility, can be used in the production of novel composite tissue engineering scaffolds. In this study, we fabricated a PLGA/Fibrin scaffold which was evaluated to the enhancement of adipose-derived stem cells' growth and proliferation. Materials and Methods: 10% polymer solutions with different ratios of PLGA:Fibrin, including 10:0, 9:1, 8:2, and 7:3, were prepared and used in the production of aligned and unaligned electrospun nanofiber scaffolds. Human adipose-derived stem cells (h-ADSCs) were cultured on the scaffolds and they were characterized using FTIR, EDX, SEM, mechanical, hydrophilic, degradation, water absorption, and biocompatibility tests. Results: The obtained scaffolds consisted of homogeneous fibers, without any beads and water droplets. The percentage of porosities and internal correlation of the cavities are not significantly different between aligned and unaligned electrospun scaffolds (P>0.05) and by adding fibrin, these properties are improved, while tensile strength and elasticity are decreased. All the scaffolds are hydrophobic and the highest and lowest swelling rates belong to PLGA/30%Fibrin scaffolds and pure PLGA scaffolds (more than 90% and less than 45%, respectively). There is a significant difference in degradation rates between fibrin-contained scaffolds and pure PLGA scaffolds. Moreover, compared with aligned electrospun scaffolds, a higher degradation rate of unaligned ones was observed. Conclusions: Considering the results of SEM and bio-compatibility experiments, the aligned electrospun PLGA/10%Fibrin scaffold with numerous spindle shape h-ADSCs and unaligned electrospun PLGA/20%Fibrin scaffold with lots of spindle shape cells together with sort of round shape cells are introduced as the optimal options.

Precise control of microscale object rotation is essential for numerous biomedical and microelectromechanical applications. For example, somatic cell nuclear transfer for aquatic biomedical models such as zebrafish faces significant technical challenges, particularly in egg trapping and alignment of an injection needle with the micropyle. In this study, we developed a 3D resin-printed microdevice to achieve frequency-selective electrorotation of dielectric microspheres using a quadrupole electrode configuration driven by phase-shifted alternating current (AC). Theoretical analysis based on the Clausius-Mossotti factor, which governs the polarization of a particle concerning its surrounding environment, highlights the critical role of its imaginary component in the induced dipole moment from the AC field that generates torque. Simulations conducted in COMSOL Multiphysics confirmed the formation of symmetric torque-driven rotation without significant micro-scale object translation. The frequency response of angular velocity exhibited a unimodal profile, with a peak near 4 MHz corresponding to maximum torque efficiency. Experimental validation using 700-µm polystyrene microspheres in Dulbecco's Phosphate Buffered Saline demonstrated consistent clockwise rotation, with a peak angular velocity of 8.1 Degrees/s observed at 900 kHz and 16 Vp-p. Although the experimental peak angular velocity occurred at a lower frequency than the theoretical maximum, the rotational trend followed the polarization relaxation behavior captured by Im[K cm ]. Parameter studies further revealed that increasing microscale object permittivity amplified torque generation, while higher medium permittivity reduced it, underscoring the tunability of electrorotation via dielectric properties. This work demonstrates a robust and scalable platform for manipulating large microscale objects. It lays the foundation for future applications involving biologically relevant objects, such as eggs of biomedical research models.