Reinhold H. Dauskardt

Bio: Reinhold H. Dauskardt is an academic researcher from Stanford University. The author has contributed to research in topics: Fracture mechanics & Fracture toughness. The author has an hindex of 59, co-authored 409 publications receiving 13186 citations. Previous affiliations of Reinhold H. Dauskardt include University of California, Berkeley & Center for Advanced Materials.

An ultra-sensitive resistive pressure sensor based on hollow-sphere microstructure induced elasticity in conducting polymer film

Abstract: Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.

An Artificial Solid Electrolyte Interphase with High Li-Ion Conductivity, Mechanical Strength, and Flexibility for Stable Lithium Metal Anodes.

Abstract: An artificial solid electrolyte interphase (SEI) is demonstrated for the efficient and safe operation of a lithium metal anode. Composed of lithium-ion-conducting inorganic nanoparticles within a flexible polymer binder matrix, the rationally designed artificial SEI not only mechanically suppresses lithium dendrite formation but also promotes homogeneous lithium-ion flux, significantly enhancing the efficiency and cycle life of the lithium metal anode.

A Silica-Aerogel-Reinforced Composite Polymer Electrolyte with High Ionic Conductivity and High Modulus.

Abstract: High-energy all-solid-state lithium (Li) batteries have great potential as next-generation energy-storage devices. Among all choices of electrolytes, polymer-based systems have attracted widespread attention due to their low density, low cost, and excellent processability. However, they are generally mechanically too weak to effectively suppress Li dendrites and have lower ionic conductivity for reasonable kinetics at ambient temperature. Herein, an ultrastrong reinforced composite polymer electrolyte (CPE) is successfully designed and fabricated by introducing a stiff mesoporous SiO2 aerogel as the backbone for a polymer-based electrolyte. The interconnected SiO2 aerogel not only performs as a strong backbone strengthening the whole composite, but also offers large and continuous surfaces for strong anion adsorption, which produces a highly conductive pathway across the composite. As a consequence, a high modulus of ≈0.43 GPa and high ionic conductivity of ≈0.6 mS cm-1 at 30 °C are simultaneously achieved. Furthermore, LiFePO4 -Li full cells with good cyclability and rate capability at ambient temperature are obtained. Full cells with cathode capacity up to 2.1 mAh cm-2 are also demonstrated. The aerogel-reinforced CPE represents a new design principle for solid-state electrolytes and offers opportunities for future all-solid-state Li batteries.

Design and understanding of encapsulated perovskite solar cells to withstand temperature cycling

Abstract: The performance of perovskite solar cells has rapidly increased above 22%, and their environmental stability is also progressing. However, the mismatch in thermal expansion coefficients and low fracture energy of layers in perovskite solar cells raise a concern as to whether devices can withstand mechanical stresses from temperature fluctuations. We measured the fracture energy of a perovskite film stack, which was shown to produce 23.6% efficiency when incorporated in a monolithic perovskite-silicon tandem. We found that the fracture energy increased by a factor of two after 250 standardized temperature cycles between −40 °C and 85 °C and a factor of four after laminating an encapsulant on top of the stack. In order to observe how the increased mechanical stability translated from film stacks to device performance and reliability, we carried out a comparative study of perovskite solar cells packaged between glass and two commonly used encapsulants with different elastic moduli. We demonstrated that solar cells encapsulated with a stiffer ionomer, Surlyn, severely decreased in performance with temperature cycling and delaminated. However, the solar cells encapsulated in softer ethylene vinyl acetate withstood temperature cycling and retained over 90% of their initial performance after 200 temperature cycles. This work demonstrates a need for an encapsulant with a low elastic modulus to enable mechanical stability and progress toward 25 year operating lifetime.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

Abstract: The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Fracture Mechanics of Ceramics

Abstract: The failure of ceramic materials is caused by the extension of small flaws. Therefore, linear-elastic fracture mechanics can be applied to describe the failure behaviour. The main problem in the application of the simple fracture mechanics relation is the existence of a rising crack growth resistance curve, which is caused by crack bridging forces behind the advancing crack tip or by transformations in front of the crack tip. The increasing crack growth resistance leads to problems in the transformation of results from specimens with macrocracks to components with natural cracks.