Plants suitable for extensive green roofs must tolerate extreme rooftop conditions, and the substrates in which they grow must fulfill horticultural and structural requirements. Deeper substrates may retain more water for plants during dry periods, but will also weigh more, especially when near saturation. A study in central Pennsylvania was conducted to evaluate the influence of substrate type and depth on establishment of five green roof plants. Two stonecrops [white stonecrop (Sedum album) and tasteless stonecrop (Sedum sexangulare)], one ice plant (Delosperma nubigenum), and two herbaceous perennials [maiden pink (Dianthus deltoides) and saxifrage pink (Petrorhagia saxifraga)] were planted in three depths (30, 60, and 120 mm) of two commercially available green roof substrates (expanded shale and expanded clay). Study flats inside a plasticulture tunnel received three drought treatments (no drought, 2 weeks early drought, and 2 weeks late drought). The two stonecrops performed well under most conditions, although tasteless stonecrop was stunted by early drought. Ice plant only grew well when provided with water. When subjected to any drought, the herbaceous perennials had the fewest survivors in the expanded shale. Saxifrage pink flowered profusely wherever it survived. The study plants were most affected by substrate depth, except for maiden pink, which responded solely to drought. When subjected to early drought conditions, the herbaceous perennials did not survive in 30 mm of either substrate, or in 60 mm of expanded shale. Although the stonecrops performed well in 60 mm of substrate when subjected to drought, their performance was superior in the expanded clay compared with shale.

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A plantless system using subirrigation was developed to measure water absorption and loss in soilless media amended with hydrophilic polymers, a wetting agent, or combinations of these amendments. Peat-perlite-vermiculite and bark-peat-perlite controls achieved 67% and 52% of container capacity, respectively, after 20 daily irrigation cycles. Maximum water content of amended media was 78% of container capacity. Adding only a hydrophilic polymer did not increase total water content significantly. Adding a wetting agent increased water absorption in both media. However, when hydrophilic polymer and wetting agent were present, the medium absorbed more water than with wetting agent alone. More extractable water was removed from media containing wetting agent. Water loss rate by evaporation was not affected significantly by medium, hydrophilic polymer, wetting agent, or any combination of these variables.

Ultrasonic mid-air haptic feedback enables the tactile exploration of virtual objects in digital environments. However, an object's shape and texture is perceived multimodally, commencing before tactile contact is made. Visual cues, such as the spatial distribution of surface elements, play a critical first step in forming an expectation of how a texture should feel. When rendering surface texture virtually, its verisimilitude is dependent on whether these visually inferred prior expectations are experienced during tactile exploration. To that end, our work proposes a method where the visual perception of roughness is integrated into the rendering algorithm of mid-air haptic texture feedback. We develop a machine learning model trained on crowd-sourced visual roughness ratings of texture images from the Penn Haptic Texture Toolkit (HaTT ). We establish tactile roughness ratings for different mid-air haptic stimuli and match these ratings to our model's output, creating an end-to-end automated visuo-haptic rendering algorithm. We validate our approach by conducting a user study to examine the utility of the mid-air haptic feedback. This work can be used to automatically create tactile virtual surfaces where the visual perception of texture roughness guides the design of mid-air haptic feedback.