Impact Of Microparticles Research Articles

Modelling of micro-particles perforations into human tissue surrogate: Numerical and analytical aspects

Investigating high-speed microparticle impact responses into soft tissue is essential to several fields like medicine and transdermal delivery of pharmaceuticals. Various simulants such as ballistic gelatin, rubber, and polymers have been developed to replace the biological body in experimental investigation, considering the practical and ethical issues. The synthetic polymer SEBS gel (styrene-ethylene-butylene-styrene) interests some scientists in recent years because it involves several benefits like environmental stability, reproducibility, mechanical consistency, transparency, and biofidelic ability to reproduce human soft tissue behavior. A few experiments have been performed on the penetration of SEBS gel. But its physical behavior under high-velocity impact, especially in micro-scale, is yet to be investigated. As the earliest meshless method, Smoothed Particles Hydrodynamics (SPH) has been identified to have a great potential in simulating extremely large deformation. This study employs a numerical model by the SPH method to investigate the response of the SEBS gel under micro-penetration, combined with an elastic-hydrodynamic constitutive law. The range of Young’s modulus is firstly described for the SEBS gel under micro-impacts, which is validated against experimental data. Supplementally, the suitability of three types of analytical models depending on fitting coefficients is also discussed for micro penetrations into soft tissue.

Impact resistance of single-layer metallic glass nanofilms to high-velocity micro-particle penetration

Macro- and microscale metallic glasses exhibit excellent protective capability under hypervelocity projectile impact conditions. However, it is formidably challenging to evaluate the ballistic performance of metallic glasses with characteristic sizes down to the nanoscale. Here, we adopt the laser-induced micro-particle impact technique to penetrate 60-nm-thick Ni60Ta40 metallic glass nanofilms with projectile velocities in the range of 186–540 m/s. Based on the ballistic analysis, the superior impact resistance of the metallic glass nanofilms is quantitatively characterized in terms of the specific penetration energy. The post-mortem observations of the penetration features reveal that shear-banding, cracking, and bending of cracking-induced petals are the main energy dissipation modes beyond the localized perforated hole, which is strongly dependent on impact velocities. This work for the first time achieves high-strain-rate loading on nanoscale metallic glasses, and extends their engineering applications as promising armor materials for high-velocity impact protection.

High-velocity micro-projectile impact testing

High-velocity microparticle impacts are relevant to many fields, from space exploration to additive manufacturing, and can be used to help understand the physical and chemical behaviors of materials under extreme dynamic conditions. Recent advances in experimental techniques for single microparticle impacts have allowed fundamental investigations of dynamical responses of wide-ranging samples, including soft materials, nano-composites, and metals, under strain rates up to 108 s−1. Here we review experimental methods for high-velocity impacts spanning 15 orders of magnitude in projectile mass and compare method performances. This review aims to present a comprehensive overview of high-velocity microparticle impact techniques to provide a reference for researchers in different materials testing fields and facilitate experimental design in dynamic testing for a wide range of impactor sizes, geometries, and velocities. Next, we review recent studies using the laser-induced particle impact test platform comprising target, projectile, and synergistic target-particle impact response, hence demonstrating the versatility of the method with applications in impact protection and additive manufacturing. We conclude by presenting the future perspectives in the field of high-velocity impact.

Ballistic delivery of compounds to inner layers of the cornea is limited by tough mechanical properties of stromal tissue

The barrier characteristics of the cornea are interrogated using the impact of micro-particles into ex vivo porcine cornea. Using a commercial gene gun (BioRad; PDS1000), microparticles were accelerated and made to embed in target materials: either ballistic gelatin as a reference or corneal tissue. Statistical analysis of penetration of polydisperse spherical microparticles (5–22 μm dia.) with density of 2.5 g/cc, 4.2 g/cc, and 7.8 g/cc (soda-lime glass, barium-titanate glass and stainless steel; more limited examination of 1.1 g/cc polyethylene and 19.2 g/cc tungsten) spanned almost two decades in kinetic energy. Penetration profiles in ballistic gelatin show that the particle embedding depth is sensitive to particle size and density. In the cornea, penetration is a weak function of size and density, and the corneal stroma is an effective stopping medium for high velocity microparticles. Despite the high water content of corneal tissue (76% w/w) compared to the stratum corneum of skin (40% w/w), the resistance to penetration of the cornea is comparable to what is seen in previous research of penetration in skin tissue. Using low density polymer particles with a therapeutic agent payload, it is demonstrated that bulk material can be ballistically delivered to the central 1 cm2 of the corneal epithelium in an even layer with high bioavailability of therapeutic compound.

Processing methods and storage duration impact extracellular vesicle counts in red blood cell units

AbstractExtracellular vesicles (EVs) are active components of red blood cell (RBC) concentrates and may be associated with beneficial and adverse effects of transfusion. Elucidating controllable factors associated with EV release in RBC products is thus important to better manage the quality and properties of RBC units. Erythrocyte-derived EVs (EEVs) and platelet-derived EVs (PEVs) were counted in 1226 RBC units (administered to 280 patients) using a standardized cytometry-based method. EV size and CD47 and annexin V expression were also measured. The effects of donor characteristics, processing methods, and storage duration on EV counts were analyzed by using standard comparison tests, and analysis of covariance was used to determine factors independently associated with EV counts. PEV as well as EEV counts were higher in whole-blood–filtered RBC units compared with RBC-filtered units; PEV counts were associated with filter type (higher with filters associated with higher residual platelets), and CD47 expression was higher on EEVs in RBC units stored longer. Multivariate analysis showed that EEV counts were strongly associated with filter type (P < .0001), preparation, and storage time (+25.4 EEV/µL per day [P = .01] and +42.4 EEV/µL per day [P < .0001], respectively). The only independent factor associated with PEV counts was the residual platelet count in the unit (+67.1 PEV/µL; P < .0001). Overall, processing methods have an impact on EV counts and characteristics, leading to large variations in EV quantities transfused into patients. RBC unit processing methods might be standardized to control the EV content of RBC units if any impacts on patient outcomes can be confirmed. The IMIB (Impact of Microparticles in Blood) study is ancillary to the French ABLE (Age of Transfused Blood in Critically Ill Adults) trial (ISRCTN44878718).

Site-specific study of jetting, bonding, and local deformation during high-velocity metallic microparticle impact

In the cold-spray process, jetting is often considered a precursor to particle-substrate adhesion, but the conditions under which these phenomena occur remain unclear. This paper presents a systematic site-specific study of single-particle impact across a wide range of impact velocities for Cu particles impacting a Cu substrate. A high degree of velocity control enables identification of new behaviors that emerge in distinct velocity ranges. At the lowest velocities, we observe a fully plastic impact regime with rebound of the incident particle. As velocity increases, substrate jetting emerges even while the particle still rebounds. At the critical adhesion velocity, vcr, jetting only occurs on the substrate, leading to poor metallurgical bonding. Bonding improves as velocity increases and the particles also begin to jet, but there is an apparent maximum in bonding extent at ~1.3 vcr. This is followed by a drop in metallurgical bonding due to the ‘backward’ jetting of the particle that is associated with peeling forces on the interface. At ~1.6 vcr and above, we observe hydrodynamic penetration of the particle and possible erosion, as indicated by petalling of the substrate and burial of the particle below the substrate impact plane. Taken together, this catalog of phenomena, correlated to specific velocities, points to an impact-structure-based approach to establishing processing windows for cold spray.

On the Cover of this Issue: High Strain Rate Behavior of a Viscoelastic Gel Under High-Velocity Microparticle Impact by D. Veysset et al.

On the Cover of this Issue: High Strain Rate Behavior of a Viscoelastic Gel Under High-Velocity Microparticle Impact by D. Veysset et al.

A new soft-particle DEM model of micro-particle impact integrated adhesive, elastoplastic and microslip behaviors

Micro-particle impact is a problem of solid mechanics that is common in many applications. To address this problem, a new soft-particle DEM model of micro-particle impact is proposed, which incorporates adhesive, elastoplastic and microslip behaviors. The normal force model is developed as two contiguous loading stages: the elastic stage and the elastoplastic stage in which the transition is from the elastic deformation to fully plastic deformation. Most innovative in unloading, the normal force model is also evolved into two contiguous stages: unloading under elastic loading and unloading under elastoplastic loading in which it combines Hertz elastic model and Mesarovic-Johnson plastic model. The normal force model is further assumed as the one-way coupling with pressure-based Maw tangential model with the micro-slip behavior. Further model validations are performed by employing the experimental results in literatures. The validation results indicate that model predictions agree with the experimental data, and are demonstrated to be incredibly accurate than other models, particularly for restitution coefficients and critical sticking velocity. Furthermore we can find that the smaller size particle has a longer period of nonlinear loading, while the larger size particle has a longer period of linear loading. For tangential restitution coefficient at the small incident angle, a down trend may be due to the oscillation of the tangential force.

Development of a material model for predicting extreme deformation and grain refinement during cold spraying

Fusion-based additive manufacturing techniques such as selective laser melting, electron beam freeform fabrication cause solidification problems such as grain coarseness and high porosity. As a new technique, cold spraying (CS) can overcome such melting-induced drawbacks. In this study, a material model using dislocation dynamics was developed specifically for the CS process for describing the following five nanosecond-scale physical phenomena: strain hardening, normal-range strain rate hardening, ultra-high strain rate hardening, thermal softening and grain size evolution. A single Cu microparticle impact test was conducted, and a good agreement between experimental and model-predicted microparticle deformations was observed, indicating high model accuracy. The corresponding finite element model was established, and the individual effects of the above phenomena were discussed in detail to show that material deformation is mainly controlled by ultra-high strain rate hardening while jetting is controlled by thermal softening. Additionally, both simulated and actual grain size distributions indicated that grain refinement occurs only near the microparticle-substrate interface (mainly at the interface edge). Thus, the newly developed model could accurately reproduce the dynamic deformation behaviors of impacting particles and correctly predict grain refinement (particularly due to dynamic recrystallization).

High-Strain-Rate Behavior of a Viscoelastic Gel Under High-Velocity Microparticle Impact

Impact experiments, routinely performed at the macroscale, have long been used to study mechanical properties of materials. Microscale high-velocity impact, relevant to applications such as ballistic drug delivery has remained largely unexplored at the level of a single impact event. In this work, we study the mechanical behavior of polymer gels subjected to high-velocity microparticle impact, with strain rates up to 107 s−1, through direct visualization of the impact dynamics. In an all-optical laser-induced particle impact test, 10–24 μm diameter steel microparticles are accelerated through a laser ablation process to velocities ranging from 50 to 1000 m/s. Impact events are monitored using a high-speed multi-frame camera with nanosecond time resolution. We measure microparticle trajectories and extract both maximum and final penetration depths for a range of particle sizes, velocities, and gel concentrations. We propose a modified Clift-Gauvin model and demonstrate that it adequately describes both individual trajectories and penetration depths. The model parameters, namely, the apparent viscosity and impact resistance, are extracted for a range of polymer concentrations. Laser-induced microparticle impact test makes it possible to perform reproducible measurements of the single particle impact dynamics on gels and provides a quantitative basis for understanding these dynamics. We show that the modified Clift-Gauvin model, which accounts for the velocity dependence of the drag coefficient, offers a better agreement with the experimental data than the more commonly-used Poncelet model. Microscale ballistic impact imaging performed with high temporal and spatial resolution can serve as direct input for simulations of high-velocity impact responses and high strain rate deformation in gels and other soft materials.

Impact-induced glass-to-rubber transition of polyurea under high-velocity temperature-controlled microparticle impact

Deformation-induced glass transition in segmented elastomers has been proposed to allow highly desirable enhanced energy dissipation. In this study, we investigate the temperature-dependent microscale impact response of polyurea at a fixed impact velocity. We observe a local elevated impact energy absorption around 115 °C, which is attributed to the glass-to-rubber transition temperature under the present high-rate dynamic loading. Dielectric spectroscopy was performed, and the soft-segmental α2-relaxation was extracted and fit with a Havriliak–Negami function. The α2-relaxation frequency at 115 °C correlates well with an order-of-magnitude estimate of the equivalent frequency of deformation. This work further supports the importance of the dynamical Tg as an important consideration in the design of impact resistant materials.

Surface oxide and hydroxide effects on aluminum microparticle impact bonding

Oxides, hydroxides, and other surface films act as impediments to metallurgical bonding during cold spray impact adhesion, raising the critical adhesion velocity and reducing the quality of the deposited coating. Using a single-particle impact imaging approach we study how altering the passivating surface oxides with exposures to various levels of heat and humidity affect the cold spray critical adhesion velocity in the case of aluminum. We analyze the thickness, composition and microstructure of the passivation layers with transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR), and correlate our observations with a direct measurement of the critical adhesion velocity for each surface treatment. We conclude that exposures to temperatures as high as 300 °C for up to 240 min in dry air, or to room-temperature with humidity levels as high as 50% for 4 days, have negligible effect on the surface oxide layers, and by extension do not affect the critical adhesion velocity. In contrast, ambient-temperature exposure to 95% relative humidity levels for 4 days increases the critical adhesion velocity by more than 125 m/s, approximately a 14% percent increase. We observe that this distinct change in critical adhesion velocity is correlated with unique changes in the passivating layer thickness, thickness uniformity, crystallinity and composition resulting from exposure to high humidity. These results speak to particle surface treatments to improve the cold spray process.

Modeling micro-particles impacts into ballistic gelatine using smoothed particles hydrodynamics method

Investigating high-speed microparticle impact responses into soft tissue is essential to several fields such as medicine and biology with technological applications like transdermal delivery of pharmaceuticals. The understanding of the physical process involved in such a phenomenon is complex and few experimental tools are available to study high-velocity microparticle penetration in soft tissues, generally substituted by simulants like gels in the literature. One way to overcome these issues is to use numerical simulation as an efficient way of investigation, but also include difficulties such as accurate models for materials properties, microscale computation, and mathematical formulations. As the earliest meshless method, Smoothed Particles Hydrodynamics (SPH) has been applied in solid dynamics because of its great potentials in simulating extremely large deformation and perforation of targets by various projectiles. This paper develops an original numerical model based on SPH to study the dynamical phenomena during microscale impact of spheres into ballistic gelatin (BG), a common human tissue surrogate. By simulating a series of particle penetrations into 10 wt% BG initial velocities, the projectile trajectories and penetration depths in gelatin are investigated. The effects of the gelatin’s elastic modulus in ballistic impact are also studied. The numerical results show that this numerical model appears to be an promising approach to simulate high-velocity microparticle penetrating ballistic gelatine materials.

The Transition From Rebound to Bonding in High-Velocity Metallic Microparticle Impacts: Jetting-Associated Power-Law Divergence

Abstract A metallic microparticle impacting a metallic substrate with sufficiently high velocity will adhere, assisted by the emergence of jetting—the splash-like extrusion of solid matter at the periphery of the impact. In this work, we compare real-time observations of high-velocity single-microparticle impacts to an elastic–plastic model to develop a more thorough understanding of the transition between the regimes of rebound and bonding. We first extract an effective dynamic yield strength for copper from prior experiments impacting alumina spheres onto copper substrates. We then use this dynamic yield strength to analyze impacts of copper particles on copper substrates. We find that up to moderate impact velocities, impacts and rebound velocities follow a power-law behavior well-predicted on the basis of elastic-perfectly plastic analysis and can be captured well with a single value for the dynamic strength that subsumes many details not explicitly modeled (rate and hardening effects and adiabatic heating). However, the rebound behavior diverges from the power-law at higher impact velocities approaching bonding, where jetting sets on. This divergence is associated with additional lost kinetic energy, which goes into the ejection of the material associated with jetting and into breaking incipient bonds between the particle and substrate. These results further support and develop the idea that jetting facilitates bonding where a critical amount of bond formation is required to effect permanent particle deposition and prevent the particle from rebounding.

Neurotoxicity, oxidative stress biomarkers and haematological responses in African catfish (Clarias gariepinus) exposed to polyvinyl chloride microparticles

The aquatic environment is outrageously littered with resin pellets and particles of plastic origin which can jeopardise the health of aquatic organisms. The present study investigated the effect of polyvinyl chloride (PVC) microparticles on blood parameters, leucocytes, lipid peroxidation and antioxidant system (brain and gill) of Clarias gariepinus. C. gariepinus is a fresh water indicator species often used as model for ecotoxicological assay. Fish specimens were exposed to diets spiked with PVC microparticles (95.41 ± 4.23 μm) at the following concentrations; 0.50%, 1.50% and 3.0% and control diet for 45 days, followed by a depuration trial which lasted for 30 days. Blood and tissues (brain and gill) were sampled every 15 days interval for haematology, antioxidant enzymes and lipid peroxidation assay. The result obtained revealed that PVC orchestrated the marked alterations in haematological indices. Mean cell volume and mean cell haemoglobin values reduced significantly in all concentration treated groups and were time-dependent. Neutrophil counts decreased with a corresponding increase in PVC exposure time while lymphocytes and monocytes values showed no significant difference between the control and exposed fish groups. Glutathione peroxidase activity was altered substantially in the brain and gill of the exposed groups compared to the control. Superoxide dismutase activity was inhibited in the brain and gill of the exposed groups compared to the control, as well as the different exposed periods. Catalase activity reduced significantly in the brain of 0.5% PVC exposed groups, and also decreased in a time-dependent manner while its activity in the gill did not change significantly among the exposed groups relative to the control. Lipid peroxidation levels in the brain of PVC exposed groups increased significantly in a dose and time-dependent manner. However, PVC caused no significantly change in the gill lipid peroxidation level of the exposed fish, but elevated the lipid peroxidation levels as the exposure time increased. Acetylcholinesterase activity in the brain and gill of the exposed fish reduced substantially with increase in the exposure time. Variations in haematology, antioxidant enzymes, lipid peroxidation and acetylcholinesterase activities are indicative of oxidative stress and neurotoxicity in fish. C. gariepinus is an indispensable bioindicator to measure environmental impact of PVC microparticles.

Residual stress analysis of thin film photovoltaic cells subjected to massive micro-particle impact.

Residual stresses play a crucial role in both light-electricity conversion performances and the lifespan of photovoltaic (PV) cells. In this paper, the residual stress of triple junction cells (i.e. GaInP/GaInAs/Ge) induced by laser-driven massive micro-particle impact is analyzed with a novel method based on backscattering Raman spectroscopy. The impact process, which induces damage to the PV cells and brings the residual stress, is also investigated by optical microscopy (OM) and Scanning Electron Microscopy (SEM). The results show that the PV cells would exhibit various damage patterns. At the same time, strong residual stresses up to hundreds of MPa introduced in the damaged PV cells after impact have been analysis, providing an effective perspective to better understand the damage behavior and residual stress features of PV cells during their service life.

Material hardness at strain rates beyond 106 s−1 via high velocity microparticle impact indentation

Despite advances in mechanical testing at small scales and testing at high strain rates, studies of mechanical behavior of materials remain largely qualitative in the regimes where these two conditions overlap. Here, we present an approach based on microparticle impact indentation to determine material hardness at micron scales and at high strain rates. We employ laser ablation to impact ceramic alumina microparticles (as indenter) onto two model materials, namely copper and iron. We use real time measurements of impact and rebound velocities together with post-impact measurements of indentation volume to determine material hardness at strain rates beyond 106 s−1.

Study on Atomic Oxygen Exposure and Hard Particle Impact of Polyimide Nanocomposites

Atomic oxygen (AO) exposure and hard microparticle impact on polyimide nanocomposites were performed by a ground-based magnetoplasmodynamic accelerator and electrostatic accelerator, respectively. The computer simulation of the AO erosion of polyimide nanocomposites was carried out with Monte Carlo method. It is found that the polyimide nanocomposites are significantly more durable to AO exposure than the pure polyimide material. Besides, in the case of combined hard microparticle impact and AO exposure, the regions around craters created by hard microparticle impact are etched more intensively than the undamaged areas of the polyimide nanocomposite sample surface.

Molecular dependencies of dynamic stiffening and strengthening through high strain rate microparticle impact of polyurethane and polyurea elastomers

This study investigates the molecular dependencies of dynamic stiffening and strengthening through comparison of high strain rate impact responses of various polyurethanes and polyureas. We use an in-house designed tabletop microimpact experimental platform—the laser-induced particle impact test—to perform high strain rate impacts and measure the corresponding material response. Dynamic mechanical analysis and differential scanning calorimetry are used to show that glass transition temperature is a useful predictor of the impact response at ambient temperatures. Meanwhile, solid-state nuclear magnetic resonance spectroscopy identifies segmental dynamics as an important determinant of the variation in both dynamic stiffening and strengthening. The impact responses of polyurethanes and polyureas both show clear dependencies on the molecular weight of the soft segment. This comparison suggests the state of intermolecular hydrogen bonding plays a key role in dynamic stiffening and strengthening. This study aims to identify the molecular dependencies of the impact response and establish a foundation for further design and testing of optimal high strain rate characteristics in synthetic elastomers.

Investigation of the Resistance of K-208 Glass with Optically Transparent Al–Si–N Nanocomposite Coatings to High-Speed Microparticle Impact

Investigation of the Resistance of K-208 Glass with Optically Transparent Al–Si–N Nanocomposite Coatings to High-Speed Microparticle Impact