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Author: Elder, Theresa Marie

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    Bending and Force Recovery in Polymer Films and Microgel Formation
    (North Dakota State University, 2018) Elder, Theresa Marie
    To determine correlation between geometry and material three different model films: polymethylsiloxane (PDMS), polystyrene (PS), and polycarbonate (PC), were singly bent and doubly bent (forming D-cones). Bends were chosen as they are fundamental in larger complex geometries such as origami and crumples. Bending was carried out between two plates taking force and displacement measurements. Processing of data using moment equations yielded values for bending moduli for studied films that were close to accepted values. Force recovery showed logarithmic trends for PDMS and stretched exponential trends for PS and PC. In a separate experiment a triblock copolymer of polystyrene–polyacrylic acid–polystyrene was subjected to different good and bad solvent mixing with any resulting particle morphology examined. Particles formed more uniformly with high water concentration, particles formed with high toluene concentration and agitation yielded three separate morphologies.
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    Adhesion With Slender Structures: Tape Loops, Crumples, and Origami
    (North Dakota State University, 2021) Elder, Theresa Marie
    The desire for improved adhesive systems led us to examine three geometries: tape loops, crumples, and origami shapes. The tape loop is mechanically interesting because it is stable in more than one configuration. For example, the first configuration is a circular loop. The second is an elongated oval shape that occurs after the loop is pushed into a surface. In this work we examined this cycle and derive a simple mathematical model. We found a solution to the model that only needs one input measurement, that of the loop radius, to determine a tape loop’s adhesion. We explored how a sticky but crumpled film adhered to smooth and rough surfaces. To do this we crumpled inextensible sheets because crumples have been shown to maintain a high compliance while increasing contact area through deforming around obstacles. We found that there was no significant difference in the adhesive behavior of the crumples on rough surfaces compared to flat surfaces. Finally, we designed a switchable adhesive based on thin film origami. We examined a unit cell of the Ron Resch pattern which had two different configurations (open and closed) aided by a 3-D printed device In the closed state the device had a high pull off force, and in the open state a different style of peel off occurred, lowering the peak force. We present promising results that show this to be the case.