Oligonucleotide-spider silk conjugates can be placed on silicon wafers by complementary DNA strands, which are coupled chemically to the surface. Such specific immobilization of spider silk proteins allows the nucleation and guided growth of β-sheet-rich nanofibrils in the presence of phosphate ions on the surface. Adjustment of the concentration of the immobilized conjugate, phosphate concentration and time of the assembly reaction enables control over fibril surface density and length. Furthermore, soft lithography was used to direct the conjugates on predetermined spots with a submicron resolution yielding high contrast surface patterns. This approach, which combines bottom-up and top-down surface structuring, opens up new possibilities in protein fibril based bionanotechnology.
Centralized manufacturing and global supply chains have emerged as an efficient strategy for large-scale production of goods throughout the 20th century. However, while this system of production is highly efficient, it is not resilient. The COVID-19 pandemic has seen numerous supply chains fail to adapt to sudden changes in supply and demand, including those for goods critical to the pandemic response such as personal protective equipment. Here, we consider the production of the non-woven polypropylene filtration media used in face filtering respirators (FFRs). The FFR supply chain’s reliance on non-woven media sourced from large, centralized manufacturing facilities led to a supply chain failure. In this study, we present an alternative manufacturing strategy that allows us to move towards a more distributed manufacturing practice that is both scalable and robust. Specifically, we demonstrate that a fiber production technique known as centrifugal melt spinning can be implemented with modified, commercially-available cotton candy machines to produce nano- and microscale non-woven fibers. We evaluate several post processing strategies to transform the produced material into viable filtration media and then characterize these materials by measuring filtration efficiency and breathability, comparing them against equivalent materials used in commercially-available FFRs. Additionally, we demonstrate that waste plastic can be processed with this technique, enabling the development of distributed recycling strategies to address the growing plastic waste crisis. Since this method can be employed at small scales, it allows for the development of an adaptable and rapidly deployable distributed manufacturing network for non-woven materials that is financially accessible to more people than is currently possible.
Significance Advances in material fabrication have made it possible to produce materials with an increasing range of geometries, including those with no precedent in nature. However, the relationships between geometry and state or the dynamics governing transitions between states in condensed material systems are not well understood and remain difficult to observe. Here, we use evaporating liquid droplets with a capacity for motion in response to long-range vapor-mediated interactions to create a new class of condensed matter system. The role of long-range interactions is understood by developing a simple, numerical model. A key feature of this system is the ability to rapidly fabricate nearly any 2D pattern and observe the motion of interacting elements at the macroscale.
Agaves are robust, draught tolerant plants that have been cultivated for their high-strength fibers for centuries and they hold great promise as a crop in the face of increasing water scarcity associated with a warming planet. Meanwhile, millions of women lack access to sanitary products to safely manage their menstruation particularly in low- and middle-income countries characterized by a dry climate. To address this issue, we show a processing route that transforms the leaves of the succulent Agave sisalana into a highly absorbent and retentive (23 g/g) material. The process involves delignification combined with mechanical fluffing to increase affinity for water and porosity, respectively. This process leads to a material with an absorption capacity exceeding those found in commercially available products such as menstrual pads. Finally, the carbon footprint water usage associated with this process is comparable with common alternatives with the added benefit that it can be carried out at small scales while remaining environmentally sustainable. Our work represents a step towards distributed manufacturing of essential health and hygiene products based on a local bioeconomy.
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