Tough Mechanical Properties Research Articles

Design and manufacture of structure-function integrated carbon fiber reinforced plastics for composite construction

Structure-function integrated composite can replace traditional structural components to bear loads, offering an innovative solution to reduce overall weight while storing energy in aircraft composite wings. The structural electrolyte featuring high ionic conductivity and tough mechanical properties is one of the vital components to realize high-performance multifunctional structural composite batteries. Herein, a functional ternary hydrogel electrolyte (i.e., MAP electrolyte) is elaborately engineered through the strategical incorporation of multiple hydrogen bonding among polyacrylamide (PAM) with rigid-reinforcing aramid nanofibers (ANFs) and ion-conductive Ti3C2Tx MXene nanosheets. Accordingly, the ANFs fortify the fracture toughness and self-healing properties of MAP hydrogel, and the MXene enables a doubled ionic conductivity of MAP electrolyte (32.48 mS cm−1) than that of pure PAM (16.18 mS cm−1). In addition, the capacity retention of the MAP-based full cell (81.9 %) is double of the liquid electrolyte (40.6 %) within 1000 cycles at 1 A g−1. Impressively, the MAP electrolyte remarkably enhances the flexural performance of structural batteries, with a flexural modulus (14.5 GPa) nearly three times that of structural batteries with liquid electrolytes (5.3 GPa) due to hydrogen-bonded ANFs. Simulation results and mechanical-electrochemical tests further underscore the imperative functions of MAP electrolyte as a structural component to empower the stiffness and maintain the integrity of structural batteries. Moreover, fabricating curved wing scaled components utilizing multi-point flexible forming technology demonstrates the practical feasibility of replacing structural components with complex shapes. This work will expedite the exploitation of structural battery prototypes and their real applications in EVs, UAVs, and electric-powered maritime vehicles.

Nacre‐Mimetic Multi‐Mechanical Synergistic Ceramic Aerogels with Interfacial Bridging and Stress Delocalization

AbstractElastic ceramic aerogels are exceptionally suitable for thermal insulating applications, but lacking multi‐mechanical synergistic high strength remains a deficiency. Inspired by the robust protective shells of mollusks in nature, which feature distinct hierarchical ordered structures, exhibiting strong and tough mechanical properties, a system construction and structural governing strategy is proposed to allow the nanostructure to assemble strong and flexible ceramic aerogels. Through the design of a hierarchical multi‐arched structure configurated binary‐soldering‐assemble interfacial topology interlocking, concentrated stress is effectively discrete. This biomimetic strategy enables the effective dissipation of mechanical energy, resulting in ceramic aerogels with exemplary compressive resilience, bendability, tensile resistance, and their strength exceeding that of other nanofibrous aerogels by up to tenfold. Additionally, the flexible aerogels also show remarkable thermal resistance from −196 to 1100 °C and superior thermal insulation capabilities (39.72 mW m−1 K−1), making them more suitable for the applications.

Constructing reactive “rod-bead” nanohybrid-driven high-efficient crosslinking network for the preparation of strong and tough plant protein adhesive

There still exist challenges to regulate the crosslinking network of soybean flour (SF) precisely with both strong and tough mechanical properties to match adhesion requirements of wood adhesives applications. Herein, a novel nanohybrid crosslinker with dynamic bonding effect was synthesized and then employed to improve SF adhesives. Dimethylglyoxime as chain extender was incorporated into polyurethane cooperating with CuO to form dynamic coordination bonds, after which epoxy and siloxane dual-functionalized polyurethane was co-deposited onto cellulose nanocrystal (CNC) surface to construct reactive “rod-bead” nanohybrid named CuOGU@CNC. It is found that epoxy groups induce CuOGU@CNC to form covalent crosslinking interactions with SF matrix constructing a stable adhesive system. Meanwhile, the dynamic coordination bonds of dimethylglyoxime and CuO serve as sacrificial units to contribute for energy dissipation, during which the unique “rod-bead” structure increases contact efficiency between DMG and CuO to optimize bonding exchange rate to high-effectively redistribute stress during loading. Given on the effect, the adhesives modified by CuOGU@CNC present improved dry and wet adhesion strength, and adhesion toughness compared to pristine SF sample. This work can provide a facile strategy to prepare high-performance wood adhesives aiming to meet higher applicational standard.

Mussel-inspired near-infrared light-responsive gelatin-based hydrogels for enhancing MRSA-infected wound healing

Infected wound management is a great challenge to healthcare, especially in emergencies such as accidents or battlefields. Hydrogels as wound dressings can replace or supplement traditional wound treatment strategies, such as bandages or sutures. It is significant to develop novel hydrogel-based wound dressings with simple operation, inexpensive, easy debridement, effective antibacterial, biocompatibility, etc. Here, we designed a novel gelatin-based hydrogel wound dressing Gel-TA-Fe3+. The hydrogels used tannic-modified gelatin as the main body and Fe3+ as the crosslinking agent to achieve a controllable rapid sol-gel transition. The hydrogels exhibited tough mechanical properties, excellent antibacterial ability, biocompatibility and an acceptable temperature response to near-infrared light (NIR). Moreover, the hydrogels could promote the healing process of MRSA-infected skin wound in rats. This multifunctional hydrogel was thought to have potential for emergency treatment of bacterial infected wound.

In-situ polymerization of a free-standing and tough gel polymer electrolyte for lithium metal batteries

In-situ polymerization of gel polymer electrolyte (GPE) is expected to be promising approach to solve the safety and interfacial problems of lithium ion battery, but it is still challenging ways to tradeoff the high electrochemical properties and mechanical toughness. Here, 30 μm thickness of free-standing GPEs with extremely high monomer conversion were obtained by in-situ UV approach on lithium metal anode within only few seconds. The coordination of amide and aliphatic carbonyl groups with lithium ion endows the tough mechanical properties, which tensile strength and elongation at break reach up to ∼1.0 MPa and ∼920 %. Furthermore, the inflammability of dry polymer matrix and a good degree of graphitization on the surface of burned polymer gel contribute to its flame resistance. The ionic conductivity and lithium ion transferance number are up to 1.03 mS/cm and 0.44 at room temperature, respectively. Finally, Li/LiFePO4 half cells assembled with the optimized GPEs exhibit stable cycle performance at 0.5C rate, delivering 77.44 % of capacity retention after 1000 cycles.

3D Printing of Branched Polyurethane with Tough Mechanical Properties for Stretchable Sensors

The poor mechanical properties and difficulties in manufacturing complex structures seriously limit the applications of elastomers especially in flexible electronic sensor. Herein, a series of polyether amine (PEA) grafted polyurethane acrylate oligomers (PUA‐g‐PEAs) and the corresponding low‐viscosity UV‐curable flexible 3D printing elastomers (PEA‐1/IDAs) are synthesized. The results show that a certain amount of PEA branch exactly has strengthening and toughening effect on polyurethane, resulting in 12% increase in tensile strength and 44% increase in elongation at break of PUA‐g‐PEA‐1. When mixed PUA‐g‐PEA‐1with acrylimorpholine and IDA in the ratio of 3:5:2, PEA‐1/IDA‐20 with best overall mechanical properties is obtained. Its tensile strength and elongation at break are 18.5 MPa and 297.4%, respectively. The unprecedented fatigue resistance of PEA‐1/IDA‐20 ensures that it can withstand 100 compression cycles at 80% strain without damage. Besides, piezoresistive sensors and wearable finger guard sensors are fabricated by laminating a layer of conductive hydrogel on the surface of the 3D‐printed devices. The impressive mechanical properties and 3D printing producing process of this branched PUA endow it with great potentials in advanced electronic sensors.

A renewable tricyclic building block towards synthesis of biobased polyesters with high-performance and hydrolyzability

The development of biobased polyesters which concurrently achieve high‐performance and hydrolyzability, is a significant challenge. Here N,N′-trans-1,4-cyclohexane-bis(pyrrolidone-4-methyl carboxylate) (CBPC), a tricyclic diester, was prepared by Michael addition-cyclization from renewable feedstocks. Single-crystal X-ray revealed an unfolded skeleton of CBPC, in which two pyrrolidones symmetrically disposed in non-planar space around the cyclohexane. CBPC exhibited a high reactivity to be polymerized with various diols to generate biobased polyesters with high number-average molecular weight over 40 kDa. The tricyclic structure imparts the high glass transition temperature (Tg) (over 100°C), tough mechanical properties (tensile strength up to 56.8 MPa) as well as noticeable hydrolytic degradation to the resulting polyesters, which exhibit great potential to compete with commercial polyesters of polyethylene terephthalate (PET), polylactic acid (PLA) and polybutylene terephthalate (PBT). The hydrolytic pathway and reactivity site of the polyesters were further elucidated by the theoretical calculation. Note that PBT, PET and PLA are extremely reluctant to hydrolyzation, a higher sensitivity to hydrolysis is desired for high-performance polyester to reduce environmental impact. Overall, this work addresses some critical requirements for high-property polyesters which concurrently achieve high Tg values, tough mechanical properties, wide process windows, and hydrolysis quality.

Dual-Cross-Linked Chitosan-Based Antibacterial Hydrogels with Tough and Adhesive Properties for Wound Dressing.

Biocompatible chitosan-based hydrogels have attracted extensive attention in wound dressing due to their human skin-like tissue characteristics. However, it is a crucial challenge to fabricate chitosan-based hydrogels with versatile properties, including flexibility, stretchability, adhesivity, and antibacterial activity. In this work, a kind of chitosan-based hydrogels with integrated functionalities are facilely prepared by solution polymerization of acrylamide (AAm) and sodium p-styrene sulfonate (SS) in the presence of quaternized carboxymethyl chitosan (QCMCS). Due to the dual cross-linking between QCMCS and P(AAm-co-SS), the optimized QCMCS/P(AAm-co-SS) hydrogel exhibits tough mechanical properties (0.767MPa tensile stress and 1100% fracture strain) and moderate tissue adhesion (11.4kPa). Moreover, biological evaluation in vitro illustrated that as-prepared hydrogel possesses satisfactory biocompatibility, hemocompatibility, and excellent antibacterial ability (against S. aureus and E. coli are 98.8% and 97.3%, respectively). Then, the hydrogels are tested in a rat model for bacterial infection incision in vivo, and the results show that they can significantly accelerate epidermal regeneration and wound closure. This is due to their ability to reduce the inflammatory response, promote the formation of collagen deposition and granulation tissue. The proposed chitosan-based antibacterial hydrogels have the potential to be a highly effective wound dressing in clinical wound healing.

Facile preparation and properties of porous poly(vinyl alcohol)/trehalose/nano-clay hydrogels with high mechanical strength for potential application in bone tissue engineering

Among various biomaterials, hydrogels are considered as the most attractive tissue engineering material due to their resemblances to extracellular matrix. However, due to the poor mechanical properties, poly(vinyl alcohol) hydrogels are restricted to be applied in load-bearing tissue repair and regeneration. In this work, we designed a series of porous biocompatible composite hydrogels with tough mechanical properties for bone tissue engineering, consisting of poly(vinyl alcohol), trehalose and nano-clay. These novelty hydrogels were prepared by a facile one-pot method. Compositions, microscopic structures, and mechanical properties of hydrogels were investigated in detail. The maximum compressive strength, compressive modulus, tensile strength, elastic modulus, and toughness of hydrogels attained about 2.71 MPa, 0.163 MPa, 0.741 MPa, 0.084 MPa, and 0.94 MJ/m3, respectively. These as-prepared hydrogels exhibited the excellent mechanical properties, which were ascribed to the hydrogen bond interactions between molecules and nano-enhancement effect of the nano-clay. Meanwhile, as-prepared hydrogels also exhibited a three-dimensional and interconnected porous microstructure, which facilitated the transport of nutrients to promote cells growth. In addition, the mechanical properties and microscopic structures of hydrogels could be controlled by adjusting the concentrations of trehalose and nano-clay. In vitro cell experiments demonstrated that the hydrogels had good biocompatibility. And hydrogels possessed the excellent ability to induce MC3T3-E1 cells osteogenesis to accelerate bone defects repair. Above illustrated results demonstrated that the potential applications of the hydrogels used as bone tissue engineering materials. Therefore, we anticipated this kind of poly(vinyl alcohol)-based composite hydrogel could develop a new strategy for bone tissue repair.

Fabrication and testing of bioinspired microstructured alumina composites with sacrificial interpenetrating polymer bonds

Bioinspired composites exhibit well-defined microstructures, where anisotropic ceramic particles are assembled and bonded by an organic matrix. However, it is difficult to fabricate these composites where both the ceramic particles and organic matrix work together to unlock toughening mechanisms, such as shear dissipation, particle rotation and interlocking, etc, that lead to stiff, strong, and tough mechanical properties. Here, we produce composites inspired by seashells, made of alumina microplatelets assembled in complex microstructures and that are physically bonded by a small amount of interpenetrated polymer network (IPN) made of polyacrylamide (PAM) and poly-N-isopropylacrylamide (PNIPAM). The fabrication employs magnetically assisted slip-casting to orient the microplatelets as desired, and in situ gelation of the IPN, followed by drying. The process was successful after carefully tuning the slip casting and gelation kinetics. Samples with horizontal, vertical, and alternating vertical and horizontal microplatelets orientations were then tested under compression. It was found that the IPN threads bonding the microplatelets acted as sacrificial bonds dissipating energy during the compression. Paired with the alternating microstructure, the IPN significantly enhanced the compressive toughness of the composites by 205% as compared to the composites with horizontal or vertical orientation only, with less than 35% reduction on the stiffness. This study demonstrates that microstructure control and design combined with a flexible and tough matrix can effectively enhance the properties of bioinspired ceramic polymer composites.

Simultaneous Configuration of High Room-Temperature Self-Healing Efficiencies and Tough Mechanical Properties of Energetic Adhesives for Energetic Composites

Room-temperature self-healing adhesives require more flexible polymer chains and weaker interactions, which are not conducive to good mechanical properties. Therefore, an energetic self-healing adhesive containing asymmetric alicyclic structures and multiple urea groups was designed. The asymmetric alicyclic structures could form loosely packed hard domains, and the irregular arrangement of multiple continuous urea groups could strengthen the physical cross-linking and improve the strengths of the hard domains. As a result, adhesives with improved mechanical properties (tensile strength and toughness) were obtained, and their dynamic adaptabilities and responsiveness required for self-healing at room temperature were maintained. The glycidyl azide polymer-based polyurethane (GPU) adhesive (GPU-3.0) exhibited excellent comprehensive performance in terms of toughness, healing efficiency, adhesion strength, and energy level. The maximum tensile strength and toughness of the energetic composite material (ECM, GPU/Al) prepared using GPU-3.0 and Al were 2.52 MPa and 2.45 MJ m–3, respectively. After 72 h at room temperature, the scratches on the GPU/Al surface were no longer observed and the mechanical properties were completely recovered. Therefore, the designed adhesive, which displays a high-efficiency room-temperature self-healing capacity and good mechanical properties, is applicable in self-healing ECM systems. This strategy should provide insights for use in improving the stabilities and safety of ECMs.

Dual responsive self-healing hydrogels with wide stability and excellent mechanical strength based on aliphatic polycarbonate

The wide development of hydrogels had been used in many filed due to the high water-containing and tough three-dimensional structure, however, the poor mechanical and multi-functional properties of hydrogel can be limited in its applications deeply. Herein, the dual responsive self-healing hydrogels with tough mechanical properties were manufactured by dual-physical cross-linking based on biodegradable aliphatic polycarbonate. Choosing the soft and hard segments to design the polymeric hydrogel not only can facilitate the dual-dynamic bonding interactions but also the resilient hydrogels possess robust and controllable mechanical strength (6.51 MPa). Furthermore, the results of swelling and stability tests of the materials indicated that the swelling ability of the biodegradable hydrogels can be regulated by the hydrophilic group, and the maximal swelling ratio in water and the equilibrium water content is 66% and 40%, respectively. It is worth mentioning that the tough hydrogels embrace dual-responsive high efficiency of self-healing ability, and the self-healing time is 2 h at 50 °C or 10 h under pH = 5, suggesting that the obtained hydrogels can respond to temperature and pH value to drive the fracture interface for fast self-healing, which will offer new opportunities for stimuli-responsive materials and wound healing.

Analysis of the Effect of Tempering Temperature on the Formation of Microstructure and Hardness Values in SKD11 Steel

SKD11 steel is a tool steel material. SKD11 steel must have strong and tough mechanical properties. So to improve the quality and ability of SKD11 steel to accept external loads and forces, it is necessary to heat treatment. The heat treatment carried out in this research is hardening and hardening – tempering. The hardening process is carried out by heating SKD11 steel at austenitic temperature of 950 °C and holding time of 30 minutes. Then fast cooling (quenching) with water cooling media. As for the hardening – tempering process with temperature variations of 400 °C, 500 °C, 600 °C and a holding time of 60 minutes. In the as-quenching process the microstructure formed is martensite and residual austenite which cannot be transformed. Increasing the tempering temperature affects the martensite formed into tempered martensite consisting of ferrite and cementite carbide. In addition, with increasing tempering temperature the volume of carbide distribution will decrease and have a smoother shape. As the volume of carbide distribution decreases and the ferrite structure becomes more consistent, the ductility of the steel will increase and the hardness will decrease. The hardness value of SKD11 steel with hardening of 950 °C is 61.5 HRc. While the steel with hardening - tempering at a temperature of 400 °C = 57.3 HRc, 500 °C = 56.3 HRc, and 600 °C = 49,5 HRc. Increasing the tempering temperature will increase the ductility and decrease the hardenability on SKD11.

Thermally Induced Gelation of Cellulose Nanocrystals in Deep Eutectic Solvents for 3D Printable and Self-Healable Ionogels

Soft ionotronics with self-healing capability and tough mechanical properties are highly desirable for wearable sensors that monitor physiological signals. Rapid prototyping by 3D printing further expands design spaces to enhance the performance of wearable sensors. However, it remains a challenge to achieve printability, mechanical toughness, and self-healing capability simultaneously. Here, we demonstrated a simple route to 3D printable ionogels by thermally induced gelation of cellulose nanocrystals (CNCs) in a deep eutectic solvent (DES). Although DES has been used as a nonvolatile and ionic conductive medium for ionogels, a large quantity of CNCs has to be dispersed in DES to achieve the ideal rheological behavior required for the direct ink writing process. Our strategy significantly reduced the concentration of CNCs needed to prepare printable inks with strong physical networks in DES by triggering the desulfation of CNCs at high temperatures. Further, photopolymerization of acrylic acid and acrylamide with Al3+ ions in the composite inks led to ionogels that contained multiple types of dynamic bonding. Compared with common hydrogels, our DES ionogels exhibited high mechanical toughness and self-healing capability to extend the lifetime of ionotronics. The ionogels were then printed as triangular lattice structures to increase the sensitivity of wearable sensors. In short, we demonstrated a strategy to fully utilize renewable nanomaterials, CNCs, for robust wearable ionotronics.

Lignin-based vitrimer for circulation in plastics, coatings, and adhesives with tough mechanical properties, catalyst-free and good chemical solvent resistance

Lignin is the most abundant renewable natural source of aromatic compounds but is the least utilized biomass resource. In a drive to increase both the value and utilization of lignin, whilst simultaneously reducing the environmental impact of petroleum products, we have designed a solvent-resistant recyclable lignin-based vitrimer, which has excellent mechanical performance. The vitrimer, which contains 73.0% lignin, has very high tensile strength (up to 68 Mpa), high elongation at break (up to 80.0%), very good solvent resistance and multiple recycling options (hot press recycling, ethylene glycol recycling, alkali recycling). The lignin-based vitrimer can be prepared without the need for catalyst or hot press molding and can be photothermally bonded. When used as a glass coating or a rubber adhesive, it not only has very good solvent resistance, but can also be easily disassembled for recycling. This work provides an efficient and high value method for utilizing lignin and also provides practical solutions to the problems of environmental pollution caused by non-renewable plastics and under-use of biomass resources. • Vitrimer is prepared by lignin modification and self-crosslinking. • Catalyst-free ester exchange type Vitrimer. • Tough mechanical properties and multiple cycle options. • Good chemical solvent resistance.

A microscale regulation strategy for strong, tough, and efficiently self-healing energetic adhesives

In general, robust mechanical properties require a stable strong physical or covalent network inside the polymer, limiting the mobility of molecular chains and the dynamics of physical crosslinks or reversible covalent bonds. Therefore, high healing efficiency at moderate temperature and robust mechanical properties are contradictory, which is difficult to optimize simultaneously. Therefore, this study introduced a new strategy. First, acyl semicarbazides motifs were utilized to endow energetic adhesives with strong and tough mechanical properties. Then, the asymmetric structure was introduced to regulate the hydrogen bonding array density and micro-scale trim the size of the hard domain, thereby improving the hydrogen bonding dynamics and the polymer-chains mobility. Finally, the synthesized energetic polymer adhesive (EPA) exhibited excellent comprehensive ability in terms of mechanical properties, self-healing efficiency, and energy level. Hereafter, the adhesive was further to be used with Al powder for the preparation of the EPA-based energetic composite materials (EPA/ECM), which could be mechanically comparable to commercial non-energetic adhesive-based ECMs. In addition, the high crack-healing efficiency of EPA/ECM indicated that the adhesive possessed strong application potential, which is expected to provide new ideas for improving the safety and service life of energetic composites.

Sustainable polyesters via direct functionalization of lignocellulosic sugars.

The development of sustainable plastics from abundant renewable feedstocks has been limited by the complexity and efficiency of their production, as well as their lack of competitive material properties. Here we demonstrate the direct transformation of the hemicellulosic fraction of non-edible biomass into a tricyclic diester plastic precursor at 83% yield (95% from commercial xylose) during integrated plant fractionation with glyoxylic acid. Melt polycondensation of the resulting diester with a range of aliphatic diols led to amorphous polyesters (Mn = 30-60 kDa) with high glass transition temperatures (72-100 °C), tough mechanical properties (ultimate tensile strengths of 63-77 MPa, tensile moduli of 2,000-2,500 MPa and elongations at break of 50-80%) and strong gas barriers (oxygen transmission rates (100 µm) of 11-24 cc m-2 day-1 bar-1 and water vapour transmission rates (100 µm) of 25-36 g m-2 day-1) that could be processed by injection moulding, thermoforming, twin-screw extrusion and three-dimensional printing. Although standardized biodegradation studies still need to be performed, the inherently degradable nature of these materials facilitated their chemical recycling via methanolysis at 64 °C, and eventual depolymerization in room-temperature water.

Local crystallization investigation of amorphous alloys using a two-dimensional detector by X-ray diffraction method

Amorphous alloys without a crystalline structure exhibit excellent soft magnetic properties but are difficult to machine due to their tough mechanical properties. The authors have proposed a new machining method that improves machinability by crystallizing only the local regions involved in machining, thereby reducing local strength and toughness. To realize this method, it is necessary to evaluate the crystallinity of the local area nondestructively, but it is difficult to detect a local area of crystals precipitated in amorphous materials by the conventional X-ray diffraction method (sin2ψ method). In this paper, we attempted to investigate the crystallinity of the local area using a two-dimensional X-ray diffraction method (2D method) with a two-dimensional detector. Fe-based amorphous alloys were locally crystallized using an ultrashort pulsed laser with a beam diameter of about 66 μm. Then, it was revealed that the 2D method can evaluate even a small area of crystallization within several tens of micrometers.

Polymer Network Editing of Elastomers for Robust Underwater Adhesion and Tough Bonding to Diverse Surfaces

Tough adhesives with robust adhesion are desperately needed for biomedical and technological applications. However, it is extremely challenging to engineer tough and durable adhesives that are simple to make yet also exhibit strong underwater adhesion as well as tough bonding to diverse surfaces. Here, we report bioinspired elastomers based on water-immiscible polydiolcitrates, where their tough mechanical properties, robust underwater adhesion (80 kPa), and tough bonding performance (with an interfacial toughness >1000 J m-2 and a shear and tensile strength >0.5 MPa) to diverse solid materials (glass, ceramics, and steel) are actuated by the incorporation of trace amounts of additives. The additives could edit the polymer networks during the elastomer polymerization by dramatically regulating the cross-linking structures of covalent and reversible bonds, the length of polymer chains, and the hydrophobic and hydrophilic motifs, which markedly tuned the mechanical and adhesive properties of the bioelastomers. We also demonstrate versatile applications of the durable elastomers, as tough flexible joints for solid materials, superglue, tissue sealants, hemostatic dressing, and wound repair.

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.