The Dauskardt Group is particularly interested in the relationship between the chemistry and nanostructure of materials in bulk form or thin films and their thermomechanical behavior, adhesive and cohesive fracture properties, and behavior under complex loading and environmental conditions.
The underlying theme of our research is the innovation and design of high-performance nanostructured and bio-materials, enabled by leveraging the fundamental connection between material structure and resultant function at length-scales from the sub-micron to macroscopic. We work extensively on integrating new nanomaterials into emerging technologies and pioneered quantitative methods now widely used in the device industry for characterizing adhesion and cohesion in thin-film structures. Other research areas center on probing the mechanical and treatment-response characteristics of biological tissues, with a focus on how changes in tissue structure and properties influence damage mechanisms or tactile perception. Experimental studies are complemented by a range of multiscale computational activities involving finite element and molecular dynamics simulations. Our research includes interaction with a wide range of scientific investigators nationally and internationally in academia, industry, and clinical practice.
Research in our group involves three main areas: Nanostructured Materials and Devices, Solar Modules, and Biomaterials and Regenerative Medicine. Our research on Nanostructured Materials and Devices focuses on nanomaterials design and integration for thin-film structures in nanoscience and energy technologies. Our investigation into the area of Solar Modules focuses on the development of scalable, open-air processing to produce large area next-generation perovskite modules. We also aim to enhance the operational stability of these perovskite modules through the application of layered barrier films and encapsulation strategies, while investigating the main degradation mechanisms of the Silicon solar modules which currently dominate the solar market. Finally, our studies in the area of Biomaterials and Regenerative Medicine explore the intimate relationship between the biomechanical properties of tissues and their vital underlying functions. Primarily, we explore the role of human skin as both a protective barrier for the body and a sensory organ. We study the effects of environmental factors, mechanical and projectile damage, and a wide variety of skin-care treatments on the ability of the skin to perform these functions properly. We give special attention to the 20 micron thin, outermost layer of human skin called the Stratum Corneum. The role this unique layer plays in overall skin function is critical in our understanding of tactile perception and related neurological science, as well as in the effective design of skin-care treatments to decrease discomfort or prevent damage. In addition to our experimental focus, we use finite element analysis to model macroscopic deformations in the skin with detail down to the subcellular level.
Nanostructure Materials and Devices
Karsu Ipek Kilic and Yang Wang work on nanostructure materials. We address fundamental questions related to the mechanical and thermal properties of molecular hybrid materials that have application for emerging aerospace and microelectronic technologies. Low-density hybrid materials, which contain organic and inorganic molecular components, can be engineered over a wide range of length scales to exhibit unique combinations of mechanical, thermal, and optical properties desirable for use in mechanically-robust, multifunctional aerospace applications. Hybrid materials are therefore ideally suited to a bottom-up materials design where molecular structure and resulting properties can be engineered and tailored to achieve desired property sets. Hybrid material is also an ideal platform for studying the science of molecular level confinement, we have demonstrated substantial confinement effect on polymer chain mobility, crosslinking property as well as mechanical toughening property.
Yang Wang is in charge of the experiments of nano scale hybrid materials. Current focus is on understanding thermo mechanical properties of hybrid material. Using spectroscopy methods as well as mechanical testing, the thermal oxidative degradation of nano hybrid materials could be quantitatively determined. The comparative study of degradation with and without confinement gives us insight into the role nanoscale confinement plays in the degradation kinetics of polymers.
Karsu Ipek Kilic works on computational modeling of hybrid materials. A fundamental understanding of the structure-property relationships is crucial for the thermomechanically reliable design of these materials. Through molecular dynamics simulations, we can simulate highly accurate model hybrid glass networks with varying structural characteristics such as the nanoporosity level, organosilane precursor geometry and mean network connectivity. We predict the fracture, elastic and thermal properties of these model networks by molecular dynamics simulations to explore the effects of these structural details on the resulting properties to ultimately design new hybrid materials with unusual mechanical properties.
Nick Rolston, Justin Chen, and Austin Cristobal Flick work on low-cost perovskite solar manufacturing. Implementing our demonstrated open-air, rapid spray processing techniques with a cheap and earth-abundant perovskite absorber material, our goal is to make significant steps towards reductions in manufacturing costs necessary to provide a new light-weight and low-cost PV form factor with improved materials efficiency that can compete with incumbent Si-based PV. We are working to mitigate the foremost barriers to wide-scale commercial deployment, namely perovskite module manufacturing and reliability, providing momentum towards commercialization for perovskite technology. We have achieved high performing perovskite modules and demonstrated that our deposition method operates at the highest reported throughput for perovskites and the lowest cost of any solar technology. Current efforts are focused on characterizing fundamental optoelectronic properties in the open-air processed perovskites while validating reliability with both indoor and outdoor accelerated reliability studies on modules. The use of innovative cell and interconnection architectures with mechanically robust inorganic charge transport layers, light-weight/flexible substrates, barriers and encapsulants with proven durability provide an attractive industrially-relevant form-factor for field deployment within 5 years.
Austin Cristobal Flick has been pioneering the efforts on large-area module development and design, developing unique laser-scribing methods for monolithically integrated series interconnections compatible with an optimized module geometry, enabling high-throughput module production over a wide range of device areas.
Justin Chen is leading efforts on atmospheric plasma diagnostics by using several metrologies to measure reactive oxygen and nitrogen species (RONS) identities and optical emissions unique to plasma. The finely-tuned control of process parameters enables uniform and high-quality perovskite films.
Oliver Zhao and Ziyi Pan lead the efforts on developing encapsulation strategies to protect both perovskite and bifacial silicon solar modules from degrading in environmental conditions of UV sunlight, rain/moisture, and thermal cycling of the night and day. We employ two major strategies: a thin film barrier strategy which is compatible with flexible and thermally sensitive substrates and a bulk encapsulation strategy which is more mechanically robust and allows for enhanced protection. Our thin film barriers are deposited using a scalable open-air plasma deposition process similar to the technique used for perovskite deposition. The bulk encapsulation is composed of a clear adhesive used to adhere either a plastic backsheet or a sheet of glass to protect the module from UV light as well as contaminant/moisture ingress. The eventual goal is to ensure that the efficiency of our modules can be maintained to achieve a 30-year lifetime.
Cross-section SEM image of thin film barrier structure:
Patrick Thornton helms this subgroup's efforts on studying the thermomechanical reliability of silicon solar modules, particularly the polymer encapsulant layer that protects the cells. Understanding the fundamental degradation mechanisms critical to ultimate delamination and failure of the polymer components (including the encapsulants and backsheet structures) within solar modules is paramount to extending their lifetimes, especially in adverse, terrestrial environments. This work involves indoor, accelerated and natural, outdoor testing in conjunction with advanced characterization techniques conducted both here at Stanford and at SLAC National Accelerator Laboratory. In addition, extensive work is done to apply the fundamental knowledge to predictive models to make our work even more valuable to the development and deployment of current and future materials solutions.
Biomaterials and Regenerative Medicine
Ross Bennett-Kennett studies the role that our skin plays in sensory perception. Changes to the stress state in the Stratum Corneum can lead to profound changes deep into the tissue where mechanoreceptors translate deformation into electrical signals in our brain. These perceptions drive how we feel and interact with the world around us. Additionally, we have begun a thrust to explore the role of mechanics in the health of other biological systems such as cardiovascular tissue and tendons in partnership with Stanford Medicine.
Christopher Berkey studies the resistance of human skin to projectile impact while developing an adhesive protective equipment solution to guard against impact damage without compromising user mobility. Part of this work includes characterizing and classifying wound formation mechanisms at play in the skin during dynamic impact. Additional research areas focus on the outermost layer of human skin, known as the Stratum Corneum (SC), which moderates the diffusion of water or skin-treatments in or out of the body, provides mechanical stiffness to the skin, and guards against environmental insults. Chris has performed numerous mechanical and spectroscopic studies to probe the biomechanical, structural, and functional properties of the SC. A key driving force for damage (i.e. cracking or chapping) in this critical barrier is the biomechanical stress that develops during drying. Chris’s most recent work in this area involves measurement of this stress and the development of a mechanics model to understand and then predict the influence of skin-care treatments or environmental factors (such as UV radiation from solar exposure) on stress, skin damage, and tactile perception.
Sebastian Hendrickx-Rodriguez works on engineering novel treatments and appliques by elucidating the structure-property design principles of stratum corneum. The outermost layer of skin, known as the stratum corneum (SC), is the primary barrier responsible for both protecting us against a wide range of environmental threats and maintaining proper hydration levels within our body. After millions of years of evolution, the SC has fine-tuned its biomechanical and barrier properties by forming a detailed, hierarchical structure with length scales spanning several orders of magnitude. Sebastian is interested in how various external factors, such as changes in the environment and application of cosmetic formulations, affect this structure and in turn the SC's properties.
Joseph Pace uses finite element models to understand how changes in state of the stratum corneum affect underlying tissue and how these changes are perceived. Finite element simulations of the skin suggest that strains from stratum corneum contraction propagate into the underlying layers of skin at depths that would stimulate a response from the sensory neurons that innervate cutaneous mechanoreceptors, resulting in the perception of skin discomfort. Finite element models of the skin informed by experimental data can further elucidate the mechanics of perception, which could be informative for designing more comfortable cosmetic treatments and products that adhere to the skin.
Omar El Safty works on developing structurally accurate computational models of full thickness skin in order to better understand the role the skin’s microstructure plays in its mission to protect our bodies, adapt to different temperature conditions, and adjust to complex body motions. Using profilometry and microscopy techniques, we can obtain accurate data on the skin’s topography. This data can then be used to generate finite element models that not only account for the difference in the material properties of the layers of the skin, such as the stratum corneum, the living epidermis, the dermis, and the hypodermis, but also take into account the role the stratum corneum’s topography plays in perception and dehydration, and the necessity of the epidermal-dermal boundary’s structural complexity for preventing delamination of the skin layers. Currently, the models are being used to analyze perception, the effect of different skin treatments, as well as skin damage, tearing, healing, and protection.