In this paper, we investigate the buckling of an oil-water interface populated by micron-sized latex particles using a Langmuir trough. In this work, we extend results of buckling of particle-laden interfaces from the millimeter down to the submicron range while investigating the effect of a different capillary length on the resulting wavelength. The experimental data is compared to the existing theoretical framework. An unexpected deviation from the prediction of theory of the dominant wavelength of buckling is observed for particles smaller than one micron. Those observations suggest that there is a transition to a new buckling regime involving the formation of trilayers below one micron. For the first time in particle rafts, cascading of the dominant wavelength similar to that observed in thin polymer films is reported. In addition a series of transitions between wavelengths not observed in thin films is observed within the same particle raft. Lastly, the effect of compression history on the macroscopic arrangement of particles is investigated, along with its effect on the buckling wavelength.

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In this paper, we investigate the buckling of an air-water interface populated by lycopodium powder particles using a specially designed Langmuir trough with side walls that deformed affinely with the particle-laden interface in order to minimize the effect of shear during compression. Confinement effects from the side walls were studied by systematically reducing the width of the Langmuir trough and measuring the buckling wavelength. For interfaces wider than 20 mm, the bulk wavelength was found to be independent of interface width. Due to the presence of contact line friction along the sidewall, the amplitude and wavelength of the wrinkles near the side walls were found to be reduced by a factor two compared with the bulk. A cascade in wavelength was observed as one moved from the center of the particle-laden interface towards the sidewalls similar to what has been observed for thin floating polymer films. For interface widths less than 20 mm, the wavelength of the wrinkles in the bulk was found to decrease eventually approaching the wavelength measured along the side walls. The wavelength at the walls was not affected by confinement. At large compressive strains, a transition from wrinkles to folds was observed. These regions of strain localization formed as a train of folds shortly after the onset of wrinkling and grew in amplitude with increasing compression. Confinement was also found to have an impact on folding. To study the impact of shear during interface compression, a series of objects including circular cylinders and rectangular prisms were placed through the center of the particle-laden interface before compression. These objects enhanced wrinkling and folding upstream of the object, eliminated wrinkling and folding in a broad region downstream of the object, and realigned the wrinkles along the side of the immobile obstacles where shear strains were maximum.

These definitions are for the purposes of the Grid-interactive Efficient Buildings Technical Report Series. They may be defined differently or more generally in other contexts. Grid services Services that support the generation, transmission, and distribution of electricity and provide value through avoided electricity system costs (generation and/or delivery costs); this report focuses on grid services that can be provided by grid-interactive efficient buildings. Distributed energy resource (DER) A resource sited close to customers that can provide all or some of their immediate power needs and/or can be used by the utility system to either reduce demand or provide supply to satisfy the energy, capacity, or ancillary service needs of the grid. Load profile A building's load profile describes when-time of day or hour of the year-the building is consuming energy (typically used to refer to electricity consumption but can also describe on-site fuel use); load shape and load curve are often used interchangeably, but all refer to the timing of energy use. Energy efficiency Ongoing reduction in energy use to provide the same or improved level of function. Demand flexibility Capability of DERs to adjust a building's load profile across different timescales; energy flexibility and load flexibility are often used interchangeably with demand flexibility. Demand response Change in the rate of electricity consumption in response to price signals or specific requests of a grid operator. Demand-side management The modification of energy demand by customers through strategies, including energy efficiency, demand response, distributed generation, energy storage, electric vehicles, and/or time-of-use pricing structures. Grid-interactive efficient building (GEB) An energy-efficient building that uses smart technologies and on-site DERs to provide demand flexibility while co-optimizing for energy cost, grid services, and occupant needs and preferences in a continuous and integrated way. Smart technologies for energy management Advanced controls, sensors, models, and analytics used to manage DERs. GEBs are characterized by their use of these technologies.