Structural Reinforcement through Liquid Encapsulation

The liquid inside a solid material is one of the most common composite materials in nature. The interface between solid–liquid plays an important role in unique deformation. Here, model systems of two polymers (polydimethylsiloxane–polyvinylidenefluoride) are used to make sphere of solid with liquid inside it

High-K dielectric sulfur-selenium alloys.

Upcoming advancements in flexible technology require mechanically compliant dielectric materials. Current dielectrics have either high dielectric constant, K (e.g., metal oxides) or good flexibility (e.g., polymers). Here, we achieve a golden mean of these properties and obtain a lightweight, viscoelastic, high-K dielectric material by combining two nonpolar, brittle constituents, namely, sulfur (S) and selenium (Se). This S-Se alloy retains polymer-like mechanical flexibility along with a dielectric strength (40 kV/mm) and a high dielectric constant (K = 74 at 1 MHz) similar to those of established metal oxides. Our theoretical model suggests that the principal reason is the strong dipole moment generated due to the unique structural orientation between S and Se atoms. The S-Se alloys can bridge the chasm between mechanically soft and high-K dielectric materials toward several flexible device applications

Boxception: Impact resistance structure using 3D printing

The emergence of 3D printing has enabled scientists to innovate complex geometrical designs in materials which are unattainable using conventional synthesis methods. The topological material design is becoming a common occurrence aided by 3D printing. This work reports on a high load?bearing structure by leveraging geometry using simple elastic polymers. We use the �Boxception� concept commonly used in packaging to design a structure where the open cubes are joined at their edges. The modeled structure is then printed with help of a 3D printer using polyvinyl alcohol (PVA) filament. Such design allows the outer boxes to act as shielding members to the inner?most box. Both experimental and finite element methods (FEM) are used to understand the deformation response of the structure. Experimental investigations through compression and high impact tests along with finite element simulations conclude the inherent ability of the boxception structure to prevent failure of the inner box due to the dispersed force distribution offered by the unique structure. It is further shown that the improvement in impact and load?bearing capacity is greatly influenced by the geometry of the structure. The unique structural design �Boxception� proposed can form primary load bearing component of sandwiched structures ensuring superior energy mitigation even under impact loads.by Seyed Mohammad Sajadi, Peter Samora Owuor, Robert Vajtai, Jun Lou, Ravi Sastri Ayyagari, Chandra Sekhar Tiwary and Pulickel M. Ajaya

Advances in 3D Printing for Electrochemical Energy Storage Systems

In the current scenario, energy generation is relied on the portable gadgets with more efficiency paving a way for new versatile and smart techniques for device fabrication. 3D printing is one of the most adaptable fabrication techniques based on designed architecture. The fabrication of 3D printed energy storage devices minimizes the manual labor enhancing the perfection of fabrication and reducing the risk of hazards. The perfection in fabrication technique enhances the performance of the device. The idea has been built upon by industry as well as academic research to print a variety of battery components such as cathode, anode, separator, etc. The main attraction of 3D printing is its cost-efficiency. There are tremendous savings in not having to manufacture battery cells separately and then assemble them into modules. This review highlights recent and important advances made in 3D printing of energy storage devices. The present review explains the common 3D printing techniques that have been used for the printing of electrode materials, separators, battery casings, etc. Also highlights the challenges present in the technique during the energy storage device fabrication in order to overcome the same to develop the process of 3D printing of the batteries to have comparable performance to, or even better performance than, conventional batteries

Nature Inspired Strategy to Enhance Mechanical Properties via Liquid Reinforcement

Solid-solid interface mechanism understanding of composite inclusions, when extended to solid-liquid interface design of composite using Eshelby theory, indicates a possibility of decreasing effective stiffness with increasing liquid inclusion in a solid matrix. In contrast, experimental evidence in the current paper suggests high stiffness and enhanced dynamic energy absorption in a soft polymer (polydimethylsiloxane) with high bulk modulus liquid inclusions (gallium). The basic deformation mechanism is governed by hydrostatic stress causing shape change of the liquid inclusion in large deformation regime and strain hardening of a soft polymer matrix. In addition, dynamic viscoelasticity and fluid motion also play a significant role. These understandings are developed here based on analytical modeling and a detailed finite element with smooth particle hydrodynamic simulations. The large deformation with viscoelasticity of gallium composite shows higher energy absorption and dissipation. Similar strategies of liquid reinforcement to compliant solid matrices are abundant in nature, for example, the intervertebral discs in the spinal cord and deep sea animal skin and lungs

Multiscale geometric design principles applied to 3D printed schwarzites

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOSchwartzites are 3D porous solids with periodic minimal surfaces having negative Gaussian curvatures and can possess unusual mechanical and electronic properties. The mechanical behavior of primitive and gyroid schwartzite structures across different length scales is investigated after these geometries are 3D printed at centimeter length scales based on molecular models. Molecular dynamics and finite elements simulations are used to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments. The results show that these structures hold great promise as high load bearing and impact-resistant materials due to a unique layered deformation mechanism that emerges in these architectures during loading. Easily scalable techniques such as 3D printing can be used for exploring mechanical behavior of various predicted complex geometrical shapes to build innovative engineered materials with tunable properties.30118FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2013/08293-72016/12340-9Agências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig

Structural Reinforcement through Liquid Encapsulation

The liquid inside a solid material is one of the most common composite materials in nature. The interface between solid–liquid plays an important role in unique deformation. Here, model systems of two polymers (polydimethylsiloxane–polyvinylidenefluoride) are used to make sphere of solid with liquid inside it

Role of Atomic Layer Functionalization in Building Scalable Bottom-Up Assembly of Ultra-Low Density Multifunctional Three-Dimensional Nanostructures

Building three-dimensional (3D) structures from their constituent zero-, one-, and two-dimensional nanoscale building blocks in a bottom-up assembly is considered the holey grail of nanotechnology. However, fabricating such 3D nanostructures at ambient conditions still remains a challenge. Here, we demonstrate an easily scalable facile method to fabricate 3D nanostructures made up of entirely zero-dimensional silicon dioxide (SiO₂) nanoparticles. By combining functional groups and vacuum filtration, we fabricate lightweight and highly structural stable 3D SiO₂ materials. Further synergistic effect of material is shown by addition of a 2D material, graphene oxide (GO) as reinforcement which results in 15-fold increase in stiffness. Molecular dynamics (MD) simulations are used to understand the interaction between silane functional groups (3-aminopropyl triethoxysilane) and SiO₂ nanoparticles thus confirming the reinforcement capability of GO. In addition, the material is stable under high temperature and offers a cost-effective alternative to both fire-retardant and oil absorption materials

Poly-albumen: Bio-derived structural polymer from polymerized egg white

Bio-derived materials could play an important role in future sustainable green and health technologies. This work reports the synthesis of a unique egg white-based bio-derived material showing excellent stiffness and ductility by polymerizing it with primary amine-based chemical compounds to form strong covalent bonds. As shown by both experiments and theoretical simulations, the amine-based molecules introduce strong bonds between amine ends and carboxylic ends of albumen amino acids resulting in an elastic modulus of ∼4 GPa, a fracture strength of ∼2 MPa and a high ductility of 40%. The distributed and interconnected network of interfaces between the hard albumen and the soft amine compounds gives the structure its unique combination of high stiffness and plasticity. A range of in-situ local and bulk mechanical tests as well as molecular dynamics (MD) simulations, reveal a significant interfacial stretching during deformation and a micro-crack diversion leading to an increased in ductility and toughness. The structure also shows a self-stiffening behavior under dynamic loading and a strength-induced aging suggesting adaptive mechanical behavior. This egg white-derived material could also be developed for bio-compatible and bio-medical applications.by Peter Samora Owuor, Thierry Tsafack, Himani Agrawal, Hye Yoon Hwang, Matthew Zeliskob, Tong Lic, Sruthi Radhakrishnan, Jun Hyoung Park, Yingchao Yang, Anthony S. Stender, Sehmus Ozden, Jarin Joyner, Robert Vajtai, Benny A. Kaipparettu, Bingqing Wei, Jun Lou, Pradeep Sharma, Chandra Sekhar Tiwarya and Pulickel M. Ajaya

Velcro-Inspired SiC Fuzzy Fibers for Aerospace Applications

The most recent and innovative silicon carbide (SiC) fiber ceramic matrix composites, used for lightweight high-heat engine parts in aerospace applications, are woven, layered, and then surrounded by a SiC ceramic matrix composite (CMC). To further improve both the mechanical properties and thermal and oxidative resistance abilities of this material, SiC nanotubes and nanowires (SiCNT/NWs) are grown on the surface of the SiC fiber via carbon nanotube conversion. This conversion utilizes the shape memory synthesis (SMS) method, starting with carbon nanotube (CNT) growth on the SiC fiber surface, to capitalize on the ease of dense surface morphology optimization and the ability to effectively engineer the CNT–SiC fiber interface to create a secure nanotube–fiber attachment. Then, by converting the CNTs to SiCNT/NWs, the relative morphology, advantageous mechanical properties, and secure connection of the initial CNT–SiC fiber architecture are retained, with the addition of high temperature and oxidation resistance. The resultant SiCNT/NW–SiC fiber can be used inside the SiC ceramic matrix composite for a high-heat turbo engine part with longer fatigue life and higher temperature resistance. The differing sides of the woven SiCNT/NWs act as the “hook and loop” mechanism of Velcro but in much smaller scale