Highly adherent wettability patterns on the substrate-independent superhydrophobic surfaces of trimethoxyoctadecylsilane modified titanium dioxide (TiO)-based coatings were prepared by using commercial photolithography. Three custom unidirectional channels with gradient wettability patterns were obtained by spatially selective wettability conversion from superhydrophobic to superhydrophilic when the coatings were exposed to ultraviolet light (∼365 nm). The movement behavior of droplets on these unidirectional channels was studied and the displacement of droplet movement was effectively controlled. Integrating the idea of gradient wettability patterns into planar microfluidic devices (microreactors), a self-driven fluid transport was achieved to realize droplet metering, merging or reaction, and rapid transport. This self-driven fluid transport with gradient wettability patterns has great potential in fabricating a new category of pump-free microfluidic systems that can be used in various conditions.

The wetting transition on submersed superhydrophobic surfaces with hierarchical structures and the influence of trapped air on superhydrophobic stability are predicted based on the thermodynamics and mechanical analyses. The dewetting transition on the hierarchically structured surfaces is investigated, and two necessary thermodynamic conditions and a mechanical balance condition for dewetting transition are proposed. The corresponding thermodynamic phase diagram of reversible transition and the critical reversed pressure well explain the experimental results reported previously. Our theory provides a useful guideline for precise controlling of breaking down and recovering of superhydrophobicity by designing superhydrophobic surfaces with hierarchical structures under water.

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Sears, Roebuck and Company uses a vehicle-routing-and-scheduling system based on a geographic information system to run its delivery and home service fleets more efficiently. Although the problems to be solved can be modeled as vehicle-routing problems with time windows (VRPTW), the size of the problems and thus practical complexity make these problems of both theoretical and practical interest. We constructed a series of algorithms, including the algorithm to build the origin-and-destination matrix, the algorithm to assign resources, and algorithms to perform sequencing and route improvement. The combination of GIS and OR techniques makes the system quite efficient. The system has improved the Sears technician-dispatching and home-delivery business; resulting in over $9 million in one-time savings and over $42 million in annual savings. The success of this application also suggests a promising link between GIS and OR techniques.

Schindler, the world's largest escalator company and second-largest elevator company, maintains tens of thousands of elevators and escalators throughout North America. Thousands of technicians are on the road each day to maintain, repair, and help in emergencies. Each technician's route requires precise and optimized planning. Schindler Elevator Corporation turned to Environmental Systems Research Institute (ESRI) to develop an automated route-scheduling and planning system. ESRI provided a geographic-information-system-integrated application that employs operations research techniques to optimize preventive maintenance operations. It relies on a series of algorithms to assign maintenance work to technicians and to create efficient day-routes by solving the periodic-vehicle-routing problem. These automated tools allow Schindler to restructure and streamline service areas. The optimization system saves over $1 million annually and increases Schindler's managers' awareness of operating revenue.