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Microneedles, including dissolvable ones made from biocompatible and biodegradable materials, have been widely studied and can potentially be used for transdermal drug delivery, disease diagnosis (sampling), skin care, etc. Characterizing their mechanical properties is essential, as being mechanically strong enough to pierce the skin barrier is one of the most fundamental and crucial requirements for them. The micromanipulation technique was based on compressing single microparticles between two flat surfaces to obtain force and displacement data simultaneously. Two mathematical models had already been developed to calculate the rupture stress and apparent Young’s modulus, which can identify variations of these parameters in single microneedles within a microneedle patch. In this study, a new model has been developed to determine the viscoelasticity of single microneedles made of hyaluronic acid (HA) with a molecular weight of 300 kDa loaded with lidocaine by using the micromanipulation technique to gather experimental data. The modelling results from the micromanipulation measurements suggest that the microneedles were viscoelastic and their mechanical behaviour was strain-rate dependent, which implies that the penetration efficiency of viscoelastic microneedles can be improved by increasing their piercing speed into the skin.

In the paper, the analysis of composite and prestressed beams using the matrix stiffness method is presented. The stiffness matrix for the frame element with a moment release at one end and the vector of equivalent nodal forces for the frame element with and without a moment release are derived. In the presented method, concrete is assumed to behave as viscoelastic material and the relaxation of the prestressing steel is also considered. Therefore, the relations between the generalized element displacements and the generalized element forces are integral and, here, are presented using the mathematical operators. Applying the linear integral operators, the solution to the problem is derived without introducing additional mathematical approximations and simplifications, besides the inevitable approximations related to the rheological properties of constitute materials, i.e., steel, concrete, prestressing and reinforcement steel. The derived relations can be applied with any concrete creep functions and for the element with a variable cross section.

The paper presents the viscoelastic analysis of composite and prestressed beams using the slope deflection method. For the fixed-end frame element, considering the viscoelastic behavior of concrete and relaxation of prestressing steel, the integral relation between the generalized element forces and the generalized element displacements, i.e., the element stiffness matrix, is derived and presented using the mathematical operators. From the element and system equilibrium equations, the integral equations of the problem with unknown displacements are formulated. Comparing to the analysis of homogeneous elastic structures, the governing equations of the problem are similar, but with integral equations instead of algebraic equations. In the presented method, the solution to the problem is derived using the linear integral operators without introducing any additional mathematical approximations, apart from the adopted rheological relations for constitute materials. In addition, the obtained expressions are general in a sense that any concrete creep functions can be used and the element can be with a variable cross section.

The paper presents the simplified matrix stiffness method for analysis of composite and prestressed beams. The method is based on the previously developed "exact" analysis method that uses the mathematical theory of linear integral operators to derive all relations without any mathematical simplifications besides inevitable idealizations related to the material rheological properties. However, the method is limited since the closed-form solution can be found only for specific forms of the concrete creep function. In this paper, the authors proposed the simplified analysis method by introducing the assumption that the unknown deformations change linearly with the concrete creep function. Adopting this assumption, the nonhomogeneous integral system of equations of the "exact" method simplifies to the system of algebraic equations that can be easily solved. Therefore, the proposed method is more suitable for practical applications. Its high level of accuracy in comparison to the "exact" method is preserved, which is illustrated on the numerical example. Also, it is more accurate than the well-known EM method.

Owing to the pavement cracking of heightening and thickening levees (HTL) caused by differential settlement, it is necessary to study the settlement prediction and differential settlement criterion for HTLs. In this study, an HTL was taken as the study object. First, leveling observation and layered settlement observation were adopted, and a generalized settlement prediction model (GSPM) that can describe both S-shaped and hyperbolic settlement&ndash, time curves was proposed. The physical meanings of GSPM parameters were analyzed. Moreover, the effectiveness of the GSPM was verified using field monitoring data. Second, finite element analysis based on a viscoelastic constitutive model was used to reveal the quantitative relationship between the differential settlement and horizontal stress of the pavement. On this basis, the differential settlement criterion was obtained. The results showed that the GSPM can unify the logistic model and hyperbolic model by introducing two morphological change parameters. In addition, the GSPM can be more widely used, more accurate, and more stable than the traditional logistic model and hyperbolic model. When an asphalt concrete pavement (whose ultimate tensile stress is 0.12 MPa) is used, the corresponding differential settlement criterion is approximately 4.3 cm. The research results can provide a reference for reasonable differential settlement control for HTLs in order to prevent pavement cracking.

3D printed polycaprolactone (PCL)-blended scaffolds have been designed, prepared, and evaluated in vitro in this study prior to the incorporation of a polyvinyl alcohol&ndash, polyacrylic acid (PVA&ndash, PAA) hydrogel for the delivery of in situ-formed sodium indomethacin. The prepared PCL&ndash, PVA&ndash, PAA scaffold is proposed as a potential structural support system for load-bearing tissue damage where inflammation is prevalent. Uniaxial strain testing of the PCL-blended scaffolds were undertaken to determine the scaffold&rsquo, s resistance to strain in addition to its thermal, structural, and porosimetric properties. The viscoelastic properties of the incorporated PVA&ndash, PAA hydrogel has also been determined, as well as the drug release profile of the PCL&ndash, PAA scaffold. Results of these analyses noted the structural strength, thermal stability, and porosimetric properties of the scaffold, as well as the ability of the PCL&ndash, PAA scaffold to deliver sodium indomethacin in simulated physiological conditions of pH and temperature. The results of this study therefore highlight the successful design, fabrication, and in vitro evaluation of a 3D printed polymeric strain-resistant supportive platform for the delivery of sodium indomethacin.