Biocompatibility of light responsive materials prepared for accommodative intraocular lenses manufacturing

AIM:To investigate the biocompatibility and bacterial adhesion properties of light responsive materials(LRM)and analyze the feasibility and biosafety of employing LRM in the preparation of accommodative intraocular lenses(AIOLs).METHODS:Employing fundamental experimental research techniques,LRM with human lens epithelial cells(hLECs)and human retinal pigment epithelium cells(ARPE-19 cells)were co-cultured.Commercially available intraocular lenses(IOLs)were used as controls to perform cell counting kit-8(CCK-8),cell staining under varying light intensities,cell adhesion and bacterial adhesion experiments.RESULTS:LRM exhibited a stronger inhibitory effect on the proliferation of ARPE19 cells than commercially available IOLs when co-cultured with the undiluted extract for 96h(P<0.05).Under other culturing conditions,the effects on the proliferation of hLECs and ARPE-19 cells were not significantly different between the two materials.Under the influence of light irradiation at intensities of 200 and 300 mW/cm^(2),LRM demonstrated a markedly higher inhibitory effect on the survival of hLECs compared to commercially available IOLs(P<0.0001).They also showed a stronger suppressive effect on the survival rate of ARPE-19 cells,with significant differences observed at 200 mW/cm^(2)(P<0.001)and extremely significant differences at 300 mW/cm^(2)(P<0.0001).Additionally,compared to commercially available IOLs,LRM had a higher number of cells adhering to their surface(P<0.05),as well as a significantly greater number of adherent bacterium(P<0.0001).CONCLUSION:LRM,characterized by their excellent non-contact tunable deformability and low cytotoxicity to ocular tissues,show considerable potential for use in the fabrication of AIOLs.These materials demonstrate strong cell adhesion;however,during photothermal conversion processes involving shape deformation under various light intensities,the resultant temperature rise may harm surrounding cells.These factors suggest that while the material plays a positive role in reducing the incidence of posterior capsule opacification(PCO),it also poses potential risks for retinal damage.Additionally,the strong bacterial adhesion of these materials indicates an increased risk of endophthalmitis.

Diphylleia Grayi-Inspired Intelligent Temperature-Responsive Transparent Nanofiber Membranes

Nanofiber membranes(NFMs) have become attractive candidates for next-generation flexible transparent materials due to their exceptional flexibility and breathability. However, improving the transmittance of NFMs is a great challenge due to the enormous reflection and incredibly poor transmission generated by the nanofiber-air interface. In this research, we report a general strategy for the preparation of flexible temperature-responsive transparent(TRT) membranes,which achieves a rapid transformation of NFMs from opaque to highly transparent under a narrow temperature window. In this process, the phase change material eicosane is coated on the surface of the polyurethane nanofibers by electrospray technology. When the temperature rises to 37 ℃, eicosane rapidly completes the phase transition and establishes the light transmission path between the nanofibers, preventing light loss from reflection at the nanofiber-air interface. The resulting TRT membrane exhibits high transmittance(> 90%), and fast response(5 s). This study achieves the first TRT transition of NFMs, offering a general strategy for building highly transparent nanofiber materials, shaping the future of next-generation intelligent temperature monitoring, anti-counterfeiting measures, and other high-performance devices.

Unleashing the Potential of Unidirectional Mechanical Materials: Breakthroughs and Promising Applications

The emergence of mechanically one-way materials presents an exciting opportunity for materials science and engineering. These substances exhibit unique nonreciprocal mechanical responses, enabling them to selectively channel mechanical energy and facilitate directed sound propagation, controlled mass transport, and concentration of mechanical energy amidst random motion. This article explores the fundamentals of mechanically one-way materials, their potential applications across various industries, and the economic and environmental considerations related to their production and use.

Influences of Stress Wave Propagation upon Studying Dynamic Response of Materials at High Strain Rates

How the wave propagation analysis plays a key role in the studies of dynamic response of materials at high strain rates is analyzed. For the wave propagation technique, the followings are important: the loading and unloading constitutive relation presumed, the positions of the sensors embedded, the interactions between loading waves and unloading waves. For the split Hopkinson pressure bar (SHPB) technique, the assumption of one-dimensional stress wave propagation and the assumption of stress uniformity along the specimen should be satisfied. When the larger diameter bars are employed, the wave dispersion effects should be considered, including the high frequency oscillations, non-uniform stress distribution across the bar section, increase of rise time, and amplitude attenuation. The stress uniformity along the specimen is influenced by the reflection times in specimen, the wave impedance ratio of the specimen and the bar, and the waveform.

Coseismic site response and slope instability using periodic boundary conditions in the material point method

This paper proposed the explicit generalized-a time scheme and periodic boundary conditions in the material point method(MPM)for the simulation of coseismic site response.The proposed boundary condition uses an intuitive particle-relocation algorithm ensuring material points always remain within the computational mesh.The explicit generalized-a time scheme was implemented in MPM to enable the damping of spurious high frequency oscillations.Firstly,the MPM was verified against finite element method(FEM).Secondly,ability of the MPM in capturing the analytical transfer function was investigated.Thirdly,a symmetric embankment was adopted to investigate the effects of ground motion arias intensity(I_(a)),geometry dimensions,and constitutive models.The results show that the larger the model size,the higher the crest runout and settlement for the same ground motion.When using a Mohr-Coulomb model,the crest runout increases with increasing I_(a).However,if the strain-softening law is activated,the results are less influenced by the ground motion.Finally,the MPM results were compared with the Newmark sliding block solution.The simplified analysis herein highlights the capabilities of MPM to capture the full deformation process for earthquake engineering applications,the importance of geometry characterization,and the selection of appropriate constitutive models when simulating coseismic site response and subsequent large deformations.

THERMAL AND THERMO-ELASTIC-PLASTIC RESPONSE OF CERAMIC-METAL FUNCTIONALLY GRADED MATERIALS—THERMAL SHOCK PROBLEM

The thermal and thermo-elastic-plastic response of newly developed ceramic-metal functionally graded materials under a thermal shock load is studied. The materials are heated at the ceramic surface with a sudden high-intensity heat flux input, and cooled at the metal surface with a flowing liquid nitrogen. Emphasis is placed on two aspects: (1) the influence of the graded composition of the materials on the temperature and stress response; and (2) the optimum design of the graded composition from a unified viewpoint of the heat insulation property and stress relaxation property. Moreover, a comparison between the thermoelastic stress and the thermo-elastic-plastic stress is also made to indicate the plasticity effect.

Acoustic Response and Micro-Damage Mechanism of Fiber Composite Materials under Mode-Ⅱ Delamination

Realizing the accurate characterization for the dynamic damage process is a great challenge. Here we carry out testing simultaneously for dynamic monitoring and acoustic emission （AE） statistical analysis towards fiber composites under mode-Ⅱ delamination damage. The load curve, AE relative energy, amplitude distribution, and amplitude spectrum are obtained and the delamination damage mechanism of the composites is investigated by the microscopic observation of a fractured specimen. The results show that the micro-damage accumulation around the crack tip region has a great effect on the evolutionary process of delamination. AE characteristics and amplitude spectrum represent the damage and the physical mechanism originating from the hierarchical microstructure. Our finding provides a novel aud feasible strategy to simultaneously evaluate the dynamic response and micro-damage mechanism for fiber composites.

A theoretical model for impact protection of flexible polymer material

The relationship between the protective performance of flexible polymer material and material parameters(elasticmodulus,viscosity coefficient)is explored,an impact collision motion equation between two bodies is establishedfrom the viscoelastic material constitutive,and the relationship between the kinematic response and the materialparameters is obtained.Based on the Kelvin constitutive model,a theoretical model for impact between the pro-tective body and the protected body is established,then the dynamic response is obtained.The feasibility of themodel was verified by drop hammer experiment,and the material parameters(elastic modulus,viscosity coeffi-cient)were obtained by formula.The model is discretized and the relationship between local impact response andmaterial parameters is analyzed.The discussion results on the relationship between the impact response and theprotective material performance indicate that adjusting the elastic modulus,viscosity coefficient,and thicknessof the protective material can effectively improve protective effect.

Theoretical and numerical research on the dynamic launch response of carbon fiber composite cartridges

Understanding the dynamic response of composite material cartridges during the firing process is of great significance for improving their reliability and safety.A theoretical model describing the dynamic response of composite material cartridges is established based on the thick-walled cylinder theory and rate-dependent constitutive model of composite materials.The correctness of the theoretical model is validated through finite element simulations of cartridge deformation.The influence of chamber pressure and cartridge wall thickness on the cartridge's deformation process and stress distribution is analyzed.The results indicate that the primary deformation of composite material cartridges inside the chamber is elastic deformation.Compared to metal cartridges,composite material cartridges require higher pressure for touching-chamber and are more prone to developing gaps after unloading to ensure smooth extraction.During the deformation process,the touching-chamber behavior of the cartridge can improve the stress distribution.Under the same chamber pressure,the touching-chamber behavior can reduce the circumferential stress by approximately 30%.The inner wall surface of the cartridge is a critical area that requires attention.The touching-chamber behavior can be facilitated by appropriately reducing the cartridge wall thickness while ensuring overall strength.This study can provide guidance for the optimization design of composite material cartridges.

ON THE RESPONSE FUNCTIONALS OF MATERIALS FOR THE IRREVERSIBLE PROCESSES OF THERMODYNAMICS

Based on the continuum physics and taking into account variation of the heat dissipation, Helmholtz free ener-gy, internal energy and exothermicity with the thermodynamic process, in this paper, the functional equations of the general-ized stress and entropy associated ivith the time and temperature are derived for the irreversible process of thermoviscoelastic-plastic materials. As an example, the response functionals of Maxwell viscoelastic materials are obtained.

Correlations of Materials Surface Properties with Biological Responses

More than 50 years have passed since it was first recognized that the surface properties, and predominantly the surface energies of materials controlled their interactions with all biological phases via their spontaneous acquisition of proteinaceous “conditioning films” of differing degrees of denaturation but usually of the same substances within any given system. This led to the understanding that useful engineering control of such interactions could thus be manifested through adjustments to those surface properties, giving significant control and utility to the biomaterials developer without requiring detailed discovery of the biological specifications of the components involved. Thus, effective selection of adhesive versus abhesive (non-stick, non-retention) outcomes for such useful appliances as dental implants versus substitute blood vessels, or water-resistant bonded structures versus clean, nontoxic ship bottoms is now facilitated with little biological background required. A historical overview is presented, followed by a brief survey of the forces involved and most useful analyses applied. Utility for blood-contacting materials is described in contrast to utility for bone- and tissue-contacting materials, demonstrating practical uses in controlling cell-surface interactions and preventing biofouling. New research directions being explored are noted, urging applications of this prior knowledge to replace the use of toxicants.

Blast response of continuous-density graded cellular material based on the 3D Voronoi model

One-dimensional blast response of continuous-density graded cellular rods was investigated theoretically and numerically. Analytical model based on the rigid-plastic hardening(R-PH) model was used to predict the blast response of density-graded cellular rods. Finite element(FE) analysis was performed using a new model based on the 3 D Voronoi technique. The FE results have a good agreement with the analytical predictions. The blast response and energy absorption of cellular rods with the same mass but different density distributions were examined under different blast loading. As a blast resistance structure, cellular materials with high energy absorption and low impulse transmit is attractive. However, high energy absorption and low impulse transmit cannot be achieved at the same time by changing the density distribution. The energy absorption capacity increases with the initial blast pressure and characteristic time of the exponentially decaying blast loading. By contract, when the blast loading exceeds the resistance capacity of cellular material, the transmitted stress will be enhanced which is detrimental to the structure being protected.

Axial response and material efficiency of tapered helical piles

Different techniques have been proposed to increase the bearing capacity of open-ended piles.Welding helices to the shaft and tapering the pile shaft could be used simultaneously to enhance the static and dynamic behaviors of these piles.This paper subjects the bearing capacity,stiffness,frictional behavior,and material efficiency of the tapered helical piles to scrutiny.Tapered helical piles are introduced herein as an alternative option to improve the material efficiency of hollow piles.Based on the Taguchi method,a series of experiments was designed and conducted.The axial responses of tapered helical piles are also investigated using finite element analyses.The results derived from loadedisplacement curves and strain gages are used to characterize the axial compression responses of tapered helical piles.The effects of tapered angle,helices diameter and helices distance are examined using dimensionless parameters,and the degree of contribution of these factors is calculated on each of the enumerated variables individually.Experimental results show that the shaft friction resistance of tapered helical piles increases continuously with the pile head settlement.Furthermore,the effect of tapered wall on the shaft friction resistance is more tangible at low stress levels.The results showed that the relative material efficiency factor of the optimum pile could be 2.5 times that of unoptimized pile with a similar quantity of material.

Development of processing windows for friction stir spot welding of aluminium Al5052/copper C27200 dissimilar materials

Friction stir spot welding technique was used to join dissimilar combinations of aluminium alloy(Al5052)with copperalloy(C27200)and friction stir spot welding windows such as tool rotational speed–dwell time and tool rotational speed?plungedepth diagrams for effective joining of these materials were developed.Using a central composite design model,empirical relationswere developed to predict the changes in tensile shear failure load values and interface hardness of the joints with three processparameters such as tool rotational speed,plunge depth and dwell time.The adequacy of the developed model was verified usingANOVA analysis at95%confidence level.Response surface methodology was used to optimize the developed model to maximizetensile strength and minimize interface hardness.A high tensile shear failure load value of3850N and low interface hardness valueof HV81was observed for joints made under optimum conditions,and validation experiments confirmed the high predictability ofthe developed model with error less than2%.The operating windows developed shall act as reference maps for future designengineers in choosing appropriate friction stir spot welding process parameter values to obtain good joints.

Advanced surface engineering of titanium materials for biomedical applications:From static modification to dynamic responsive regulation

Titanium(Ti)and its alloys have been widely used as orthopedic implants,because of their favorable mechanical properties,corrosion resistance and biocompatibility.Despite their significant success in various clinical applications,the probability of failure,degradation and revision is undesirably high,especially for the patients with low bone density,insufficient quantity of bone or osteoporosis,which renders the studies on surface modification of Ti still active to further improve clinical results.It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants.Therefore,it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration.This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical,physical and chemical treatments based on the formation mechanism of the modified coatings.Such conventional methods are able to improve bioactivity of Ti implants,but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues.Hence,beyond traditional static design,dynamic responsive avenues are then emerging.The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers.In short,this review surveys recent developments in the surface engineering of Ti materials,with a specific emphasis on advances in static to dynamic functionality,which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Mesoscale study on explosion-induced formation and thermochemical response of PTFE/Al granular jet

The dynamic formation,shock-induced inhomogeneous temperature rise and corresponding chemical reaction behaviors of PTFE/Al reactive liner shaped charge jet(RLSCJ)are investigated by the combination of mesoscale simulation,reaction kinetics and chemical energy release test.A two-dimensional granular model is developed with the randomly normal distribution of aluminum particle sizes and the particle delivery program.Then,the granular model is employed to study the shock-induced thermal behavior during the formation and extension processes of RLSCJ,as well as the temperature history curves of aluminum particles.The simulation results visualize the motion and temperature responses of the RLSCJ at the grain level,and further indicate that the aluminum particles are more likely to gather in the last two-thirds of the jet along its axis.Further analysis shows that the shock,collision,friction and deformation behaviors are all responsible for the steep temperature rise of the reactive jet.In addition,a shock-induced chemical reaction extent model of RLSCJ is built based on the combination of the Arrhenius model and the Avrami-Erofeev kinetic model,by which the chemical reaction growth behavior during the formation and extension stages is described quantitatively.The model indicates the reaction extent highly corresponds to the aluminum particle temperature history at the formation and extension stages.At last,a manometry chamber and the corresponding energy release model are used together to study the macroscopic chemical energy release characteristics of RLSCJ,by which the reaction extent model is verified.

Power Flow Response Based Dynamic Topology Optimization of Bi-material Plate Structures

Work on dynamic topology optimization of engineering structures for vibration suppression has mainly addressed the maximization of eigenfrequencies and gaps between consecutive eigenfrequencies of free vibration, minimization of the dynamic compliance subject to forced vibration, and minimization of the structural frequency response. A dynamic topology optimization method of bi-material plate structures is presented based on power flow analysis. Topology optimization problems formulated directly with the design objective of minimizing the power flow response are dealt with. In comparison to the displacement or velocity response, the power flow response takes not only the amplitude of force and velocity into account, but also the phase relationship of the two vector quantities. The complex expression of power flow response is derived based on time-harmonic external mechanical loading and Rayleigh damping. The mathematical formulation of topology optimization is established based on power flow response and bi-material solid isotropic material with penalization(SIMP) model. Computational optimization procedure is developed by using adjoint design sensitivity analysis and the method of moving asymptotes(MMA). Several numerical examples are presented for bi-material plate structures with different loading frequencies, which verify the feasibility and effectiveness of this method. Additionally, optimum results between topological design of minimum power flow response and minimum dynamic compliance are compared, showing that the present method has strong adaptability for structural dynamic topology optimization problems. The proposed research provides a more accurate and effective approach for dynamic topology optimization of vibrating structures.

Water—A Key Substance to Comprehension of Stimuli-Responsive Hydrated Reticular Systems

Thermo-responsive hydrated macro-, micro- and submicro-reticular systems (TRHRS), particularly polymers forming hydrogels or similar networks, have attracted extensive interest because comprise biomaterials, smart or intelligent materials. Phase transition temperature (LCST or UCST, i.e. low or upper critical solution temperature, respectively) at about the TRHRS exhibiting a unique hydration-dehydration change is a typical characteristic. The characterization and division of the TRHRS are described followed by explanation of their behaviour. The presented original explanation is based on merely combination of basic thermodynamical state of individual useful macromolecule chains (long-chain or coil) with inter- and intra-mutual action of attractive and repulsive intramolecular hydration forces among them being strongly dependent upon temperature. Acquainted with this piece of knowledge, a theoretical concept of really biological systems movement, e.g. muscle tissues or artificial muscle etc., can be formulated.

Biological Evaluation of Tissue-Engineered Cartilage Using Thermoresponsive Poly(<i>N</i>-isopropylacrylamide)-Grafted Hyaluronan

In order to contribute to the development of minimally invasive surgery techniques for autologous chondrocyte implantation, a novel self-assembling biomaterial consisting of thermoresponsive poly(N-isopropylacrylamide)-grafted hyaluronan (PNIPAAm-g-HA) has been synthesized as an injectable scaffold for cartilage tissue engineering. The aim of this study was to investigate the efficacy and cytocompatibility of PNIPAAm-g-HA to normal chondrocytes by using reverse transcription-polymerase chain reaction (RT-PCR) analysis and histochemical staining in preliminary in vitro and in vitro experiments. Hematoxylin and eosin staining showed homogeneous distribution of cells in the PNIPAAm-g-HA hydrogel in 3-dimensional in vitro cultivation. Alcian blue staining also indicated that abundant extracellular matrix formation, including acidic glycosaminoglycans, occurred in tissue-engineered cartilage over time in vitro. Cartilage-related gene expression patterns, which were tested in rabbit normal chondrocytes embedded in the hydrogel, were almost maintained for 4 weeks. Transforming growth factor-β1 (TGF-β1) stimulation enhanced the expression of SRY-related HMG box-containing gene 9 (Sox9) and type X collagen genes suggesting promotion of chondrogenic differentiation. Histochemical evaluation showed neocartilage formation following subcutaneous implantation of the chondrocyte-gel mixture in nude mice. Furthermore, TGF-β1 stimulation promoted production and maturation of the extracellular matrix of the in situ tissue engineered hyaline cartilage. These data suggested that PNIPAAm-g-HA could be a promising biomaterial, i.e., a self-assembling and injectable scaffold for cartilage tissue engineering.

Improvement of Characteristics of Gas Pressure Control System Using Porous Materials

In a gas governor unit, gas pressure vibration often occurs in the tube that connects the diaphragm chamber of the pilot valve to the downstream pipeline. Generally, placing a restriction such as an orifice in the tube can curb the vibration. However, because of the nonlinear flow rate characteristics of an orifice, the gain of the pressure response changes with changing amplitude of the pressure vibration. This paper proposes a method that employs porous materials for improving the characteristics of the gas pressure control system on account of their linear flow rate characteristics. A static flow rate characteristics experiment was performed and the linear flow rate characteristics of the porous materials were confirmed. Then, a series of dynamic pressure response experiments, in which an isothermal chamber replaced the diaphragm chamber, were performed to examine the dynamic characteristics of the porous materials and an orifice. The experimental results revealed that the gain of the pressure response in the isothermal chamber with the porous materials remained unchanged irrespective of changes in the pressure vibration amplitude, and they were in close agreement with the simulation results. They also indicated that the pressure gain of porous materials is smaller than that of an orifice when the amplitude of pressure vibration is small. These results demonstrate that porous materials can be employed instead of an orifice in the gas governor unit in order to improve the unit’s stability.