In prior generations, proteins were taken from horses and other animals to make glues. Petroleum-derived polymers including epoxies and cyanoacrylates have since replaced proteins owing to improved performance. These modern materials come at a cost of toxicity as well as being derived from limited resources. Ideally, replacement adhesives will be made from benign, cheap, and renewable feedstocks. Such a transition to biobased materials, however, will not occur until similar or improved performance can be achieved. We have discovered that coupling of proteins and sugars gives rise to strong adhesives. An unexpected connection was made between adhesion and Maillard chemistry, known to be at the heart of cooking foods. Cross-linked proteins bonded metal and wood with high strengths, in some cases showing forces exceeding those withstood by the substrates themselves. Simple cooking chemistry may provide a route to future high-performance materials derived from low-cost, environmentally benign components.

Evolutionary pressure has pushed many extant species to develop micro/nanostructures that can significantly affect wettability and enable functionalities such as droplet jumping, self-cleaning, antifogging, antimicrobial, and antireflectivity. In particular, significant effort is underway to understand the insect wing surface structure to establish rational design tools for the development of novel engineered materials. Most studies, however, have focused on superhydrophobic wings obtained from a single insect species, in particular, the Psaltoda claripennis cicada. Here, we investigate the relationship between the spatially dependent wing wettability, topology, and droplet jumping behavior of multiple cicada species and their habitat, lifecycle, and interspecies relatedness. We focus on cicada wings of four different species: Neotibicen pruinosus, N. tibicen, Megatibicen dorsatus, and Magicicada septendecim and take a comparative approach. Using spatially resolved microgoniometry, scanning electron microscopy, atomic force microscopy, and high speed optical microscopy, we show that within cicada species, the wettability of wings is spatially homogeneous across wing cells. All four species were shown to have truncated conical pillars with widely varying length scales ranging from 50 to 400 nm in height. Comparison of the wettability revealed three cicada species with wings that are superhydrophobic (>150°) with low contact angle hysteresis (<5°), resulting in stable droplet jumping behavior. The fourth, more distantly related species (Ma. septendecim) showed only moderate hydrophobic behavior, eliminating some of the beneficial surface functional aspects for this cicada. Correlation between cicada habitat and wing wettability yielded little connection as wetter, swampy environments do not necessarily equate to higher measured wing hydrophobicity. The results, however, do point to species relatedness and reproductive strategy as a closer proxy for predicting wettability and surface structure and resultant enhanced wing surface functionality. This work not only elucidates the differences between inter- and intraspecies cicada wing topology, wettability, and water shedding behavior but also enables the development of rational design tools for the manufacture of artificial surfaces for energy and water applications.

Biofouling disrupts the surface functionality and integrity of engineered substrates. A variety of natural materials such as plant leaves and insect wings have evolved sophisticated physical mechanisms capable of preventing biofouling. Over the past decade, several reports have pinpointed nanoscale surface topography as an important regulator of surface adhesion and growth of bacteria. Although artificial nanoengineered features have been used to create bactericidal materials that kill adhered bacteria, functional surfaces capable of synergistically providing antiadhesion and bactericidal properties remain to be developed. Furthermore, fundamental questions pertaining to the need for intrinsic hydrophobicity to achieve bactericidal performance and the role of structure length scale (nano vs micro) are still being explored. Here, we demonstrate highly scalable, cost-effective, and efficient nanoengineered multifunctional surfaces that possess both antiadhesion and bactericidal properties on industrially relevant copper (Cu) and aluminum (Al) substrates. We characterize antiadhesion and bactericidal performance using a combination of scanning electron microscopy (SEM), atomic force microscopy (AFM), live/dead bacterial staining and imaging, as well as solution-phase and Petrifilm measurements of bacterial viability. Our results showed that nanostructures created on both Cu and Al were capable of physical deformation of adhered Escherichia coli bacteria. Bacterial viability measurements on both Cu and Al indicated a complex interaction between the antiadhesion and bactericidal nature of these materials and their surface topography, chemistry, and structure. Increased superhydrophobicity greatly decreased bacterial adhesion while not significantly influencing surface bactericidal performance. Furthermore, we observed that more densely packed nanoscale structures improved antiadhesion properties when compared to larger features, even over extended time scales of up to 24 h. Our data suggests that the superhydrophobic Al substrate possesses superior antiadhesion and bactericidal effects, even over long time courses. The techniques and insights presented here will inform future work on antiadhesion and bactericidal multifunctional surfaces and enable their rational design.