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PhD Thesis_Dharamdeep Jain.pdf (5.79 MB)

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Humidity Driven Performance of Biological Adhesives

Jain, Dharamdeep
http://rave.ohiolink.edu/etdc/view?acc_num=akron1510053266807976

Abstract Details

2018, Doctor of Philosophy, University of Akron, Polymer Science.
Biological adhesives are sticky secretions or structures produced by several organisms in nature to serve roles such as locomotion, prey capture and defense. These adhesives stick in a variety of environmental conditions and can maintain their adhesion exceptionally well. The present work focuses on understanding one such environmental factor, `humidity’ and presents its correlation with the material composition in influencing the adhesion mechanism in two diverse biological attachment systems: Capture silk and Gecko setae. Understanding adhesion in these natural systems is essential with respect to humidity since many synthetic materials including glues fail in presence of water. The first and second studies focus on the glue laden capture silk produced by web building spiders. In the first study, we explored the capture silk of cobweb weaver `black widow spider’ known as `gumfoot glue’. We first investigated the chemical composition of the glue and for the first time reported that it is majorly a combination of hygroscopic organic salts (low molecular mass compounds, LMMCs) and novel glycoproteins, apart from previously known peptides. Next, we correlated the glue composition with humidity based macro and molecular level studies and showed the synergistic role of LMMCs and glycoproteins in adhesion across the range of humidity conditions. Based on the first study which showed the presence and importance of diverse LMMCs in capture silk adhesion, we designed our second study in understanding the role of LMMCs in the capture silk. Based on hypothesis that LMMC’s compositions control the maximum adhesion and viscosity trends across species, we designed the study in which by using Solution-State NMR, we first analyzed the water-soluble extract of glues for four different spider species from diverse habitats and found extract belonging to each species is a distinct combination of organic LMMCs present in varied proportions. Next, we studied the water uptake of glues and their isolated LMMCs compositions. The results showed that hygroscopic strength of LMMCs alone can’t explain the adhesion response of glues. We believe it is the chemical interactions of diverse LMMCs with glycoproteins that controls the adhesion mechanism of capture silks in presence of humidity. In the third, fourth and fifth studies, we switch to a different adhesive system and present investigations based on the hairs present on gecko feet, known as `setae’. In the third study, we first time established the chemical composition of hairs by characterizing molts from gecko feet and showed the presence of ß-keratin and unbound lipids. Also, we showed lipids in hairs were more mobile as compared to lipids in epidermal skin based on which we proposed structural arrangement of lipids and keratin in the setal hairs. The fourth study focused on understanding the role of surface lipids detected in the third study. By means of shear adhesion and contact angle experiments, we found those lipids do not affect adhesive and anti-adhesive properties respectively. The existing hypothesis of ß-keratin softening and leading to higher adhesion in presence of humidity was tested in our fifth study. By series of water uptake and NMR measurements, we found ß-keratin absorbs water and gets soft at a macro and molecular level. Friction cell based shear adhesion measurements on setae supported the hypothesis and showed an increase in adhesion with increase in humidity. The research studies presented provides a detailed account of correlation of environmentally relevant parameter, `humidity’ with the building blocks of capture silk and gecko setae and their adhesion performance. The results provide design insights in developing synthetic materials such as adhesives that can work in different humidity environments.
Ali Dhinojwala, Dr. (Advisor)
Mesfin Tsige, Dr. (Committee Chair)
Todd A. Blackledge, Dr. (Committee Member)
Miyoshi Toshikazu, Dr. (Committee Member)
Joy Abraham, Dr. (Committee Member)
210 p.
Biology; Biophysics; Materials Science; Polymers
Biomimicry, Adhesion, Spider Silk, Capture Silk, Geckos, Setae, Water, Lipids, Keratin, Glycoproteins, Hygroscopic Compounds

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Citations

  • Jain, D. (2018). Humidity Driven Performance of Biological Adhesives [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510053266807976

    APA Style (7th edition)

  • Jain, Dharamdeep. Humidity Driven Performance of Biological Adhesives. 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1510053266807976.

    MLA Style (8th edition)

  • Jain, Dharamdeep. "Humidity Driven Performance of Biological Adhesives." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510053266807976

    Chicago Manual of Style (17th edition)

akron1510053266807976
83
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This open access ETD is published by University of Akron and OhioLINK.