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Biomaterials

Biomaterials - Poster Session E

Poster C2 - The Formation of Complex Gold Wrinkles on 4D Printed Substrates

Saturday, October 26, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Surface wrinkle patterns are an important tool in various fields, such as tissue engineering, because surface topography can play a crucial role in cellular behavior and tissue regeneration (Yang et al., 2013; Sun et al., 2020; Oguntade et al., 2024). Surface wrinkles can be formed through mechanical instability driven wrinkling. This mechanism involves the mechanical contraction of a substrate to buckle a thin-film coating, thereby forming wrinkle patterns. However, achieving complex wrinkle formations—characterized by intricate and multi-directional patterns as opposed to simple, unidirectional ridges—remains challenging since specialized rigs are required. To facilitate the straightforward formation of simple and complex wrinkles, this work utilizes 4D printing to fabricate substrates capable of uniaxial and biaxial strain programming because such substrates will produce simple and complex wrinkles, respectively. 4D printing makes this possible because it involves 3D printing of smart materials, thus, introducing a stimuli-dependent and time-dependent functionality to the architectural control offered by 3D printing. By leveraging the unique control offered by 4D printing, the goal is to elucidate the relationship between substrate filament orientation, strain programming, and wrinkle morphology to expand theoretical understanding and advance strategies for creating tunable surface wrinkle patterns. To achieve this goal, we printed substrates composed of layers with varying filament orientations and tested the effect of these orientations on the wrinkle patterns that result upon activation of the substrate.

Materials and

Methods:  The approach began with the fabrication of substrates using an Ender 3 3D printer and smart material (polyurethane SMP; Figure 1). To achieve the uniaxial and biaxial strain programming necessary for simple and complex wrinkles, substrates were composed of either parallel extruded filaments (Figure 1B top) or alternating filament orientations (Figure 1B bottom). Wrinkles were formed through a process wherein a thin gold layer was applied to the samples using a sputter coater for 60s (Figure 1C). Since the polyurethane SMP is a smart material, heating it induces wrinkle formation by causing the substrate to contract buckling the gold layer (Figure 1C and 1D). The Hirox digital microscope was used to visualize wrinkles and measure strain changes.

Results, Conclusions, and Discussions: Although we expected to observe a correlation between filament orientation and wrinkle morphology, and how x-axis and y-axis strains relate to these parameters, the data collected did not consistently reflect this trend (Figure 2). The results reveal irregularities in the strain measurements, with no clear transition of y strain from positive to negative and inconsistent decreases in x-axis strain (Figure 4). While variations in wrinkle patterns are visible, the expected correlation between filament orientation and wrinkle complexity was not clearly observed (Figure 3). The images show variations and inconsistencies in wrinkle formation and strain measurements. This suggests that humidity affecting the filament during printing may have contributed to these inconsistencies. Future experiments will focus on controlling environmental factors, such as humidity, to achieve more reliable data. Preliminary findings suggest that these factors significantly impact wrinkle formation, highlighting the need for precise control of conditions to obtain consistent results.

This study advances the understanding of wrinkle formation on 4D printed substrates, highlighting practical implications. Controlling wrinkle morphology through printing parameters can lead to innovative applications in tissue engineering, where surface topography is crucial for cellular behavior and tissue regeneration. Future work will explore the scalability of these findings and their application in creating dynamic microenvironments for biomedical applications. Additionally, the potential antibacterial properties of these surfaces warrant further investigation, potentially leading to new surface modification strategies for medical and industrial uses. Future experiments will also aim to control for environmental factors such as humidity to ensure consistent and reliable data collection.

Acknowledgements (Optional):