Investigating environmental burdens and benefits of biologically inspired self-cleaning surfaces
Section snippets
Biologically inspired design and sustainability
Biologically inspired design is used as an approach to environmentally sustainable engineering. In a biologically inspired approach, a designer abstracts ideas and principles from nature. The designer then uses the abstracted principle or idea with the goal of producing an environmentally superior design. Self-cleaning surface technology inspired by observations of organism surfaces is one example. Given life's success and long history of persistence, it is logical to turn to the living world
Biological inspiration and benefits
To appreciate the potential benefits of self-cleaning surfaces, one must understand the biological phenomenon. Micro- and nano-scale surface roughness features combine with hydrophobic surface chemistries to generate the self-cleaning phenomenon. These changes create highly hydrophobic surfaces which cause water to “bead,” as shown in Fig. 1.
The beaded water quickly leaves the surface of an organism, taking contaminants with it. The self-cleaning ability is called the “Lotus Effect,” in honor
Goal scope and functional unit
The study's goal is to compare the life cycle of a self-cleaning surface created using a chemical coating to conventionally cleaned surfaces. It seeks to determine whether the environmental production burdens heavily outweigh the self-cleaning surface's use phase advantages.
The scope of the study includes the materials acquisition, production, and use phases for self-cleaning surface and conventional cleaning life cycles. It incorporates the main resources consumed and emissions generated
Results
Table 6 contains the results of the inventories for the self-cleaning coating and four conventional cleaning scenarios. Reading the table from left to right, the first two columns contain data for production and mist cleaning of the bio-inspired coating, respectively. One obtains the entire life cycle impact for one cleaning of a bio-inspired surface by summing the burdens in the first two columns. The middle columns contain data for conventional cleaning scenarios that represent an average of
Comparing self-cleaning surfaces and conventional cleaning
Self-cleaning surfaces created using the analyzed coating fail to demonstrate clear environmental superiority. The life cycle inventory summarized in Table 6 reveals comparatively large environmental burdens for self-cleaning surfaces. Some conventional cleaning scenarios dominate self-cleaning surfaces for the tabulated environmental burden dimensions. However, as Fig. 5 illustrates, coating durability can influence this result.
Despite low use phase burdens, the analyzed surface exhibits high
Summary and closure
Overall, the LCI study's outcome suggests the need for caution and deliberation on the part of those seeking sustainable engineering guidance from nature and those too quick to dismiss nature's lessons. On the one hand, imitating a feature of many living surfaces did not generate a clear environmental advantage when viewed from a life cycle perspective. On the other, a new technology demonstrated a degree of environmental competitiveness with a mature one. This latter point suggests that
Acknowledgements
We gratefully acknowledge NSF DMI 0600243 for financially supporting this project, Laura Raibeck and John Reap.
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