Date of Award

8-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Materials Science and Engineering

Committee Member

Dr. Konstantin G. Kornev, Committee Chair

Committee Member

Dr. Marek Urban

Committee Member

Dr. Igor Luzinov

Committee Member

Dr. Peter Adler

Abstract

This dissertation is structured around the development of a micro and nano-rheological instrument capable of measuring mPa·s-level viscosity of nanoliter droplets and micron thick films in a 10-20 second timeframe and using it to study the kinetics of formation of a blood clot in insects. To understand the materials science behind this clot formation, we enrich the microrheological study with studies of extensional rheology of various maturity stages of clots as well as studies of the surface tension isotherms, dynamic surface tensions, and surface rheology. To study the rapidly changing structure of the clots, we employ high magnification microscopy and scanning electron microscopy. Overall, we perform a detailed study of physical materials properties and structure of the material, which helps us better understand its outstanding performance. In Chapter 1, we introduce an engineering reader to the biological aspect of the problem and discuss the functionality of the material in an insect body. In Chapter 2, we discuss the importance of understanding multiscale rheology of the material and review the current methodologies available and their limitations with regards to the study of changing insect blood. In chapter 3, we discuss the principle of our methodology and the realization of the device with which we study the nanorheology with high precision and temporal resolution. In chapter 4, we present nanoscale viscosity measurements of blood of adult butterflies and moths: Manduca sexta, Vanessa cardui, and Danaus plexippus and discuss the significant deviations of the viscosities from the viscosity of water. In chapter 5, we present the nanorheological measurements of forming and maturing clots in the blood of M. sexta caterpillars and present the discovery of characteristic times of formation of these clots. In chapter 6, we present and discuss the fibrous and cellular structures of the forming blood clots of M. sexta caterpillars. In chapter 7, we study extensional rheology of forming blood clots of M. sexta caterpillars. In chapter 8, we discuss the structure formed in the clots in response to our extensional experiments and relate that to the functions of the clot constituents. Finally, in chapter 9, we study the materials properties of the surface of hemolymph of adult M. sexta, V. cardui, D. plexippus, and caterpillar M. sexta and relate them to the nano and microrheological measurements we performed on the material. We thus characterize the time-dependent structure-properties-performance triangles of blood and the forming blood clots in the studied insects.

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