Interface engineering and mechanics in haptics and additive manufacturing
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
The properties and mechanics of interfaces can control a material system’s engineering performance, from the object-finger interface in haptic materials to the interfaces created between tracks in additive manufacturing. These interfaces dictate the tactile perception of an object and the performance of 3D printed parts. By engineering material surfaces to control friction at the object-finger interface, we can change how an object feels. By designing material and process techniques with tailored operating parameters, we can build more advanced material structures. Identifying the mechanics at these interfaces is essential in closing existing gaps to engineer materials with greater performance, reliability, and scope. ☐ The object-finger interface, through friction and adhesion, generates the stimuli behind human touch perception. However, this interface is poorly understood due to its dynamic nature and contact of soft objects. As such, a knowledge gap is presented for practical implementation, such as advancement of tactile aids for people who are visually impaired or blind. Here, surface chemistry modification of everyday objects is achieved by coating two different colored objects with chemically distinct silane precursors. Mechanical friction characterization is performed on each surface, and analysis of these friction signals is presented as a predictor for distinct tactile perception. Congenitally blind human testing participants are able to reliably distinguish the different colored objects by touch alone, in a demonstration of surface chemistry modification as a practical tactile aid. Translating this work into more widely used polymer platforms, a polystyrene solution is selectively spray-coated onto textured surfaces as a method of durable and scalable application of chemical features onto traditional physical surface features. Morphological control of a poly(styrene)-b- poly(ethylene oxide) block copolymer coating is investigated as an additional modality of surface design. Phase-separation of the block copolymer film presents a chemically nanopatterned surface, distinct to that of a disordered film. The methods described here again undergo human testing and provide the necessary insight to design haptic cues based on microstructural control of interfaces with material chemistry. ☐ Finally, several instruments and processing methods are developed to address existing obstacles in material extrusion additive manufacturing. A novel material delivery system is developed which bypasses the current material limiting step of filament feedstock, greatly expanding the variety of materials available to the process. A second novel instrument is developed for in-process coextrusion of materials. It produces a coaxial composite core-shell track morphology, which can be directly varied during manufacturing to tune material properties throughout an object. Thermorheological modeling of a track interface provides insight for material and parametric design in order to approach bulk material properties. Additional material and process techniques are included to highlight other areas of track interface engineering. These tools and techniques create stronger parts out of more materials, and significantly progress the process from its current technological state. ☐ The work presented here shows how interfaces can dictate ultimate performance, whether for the dynamic object-finger interface or fused material interfaces. The results advance the state of interface and material engineering in the fields of haptics and additive manufacturing.
Description
Keywords
Additive manufacturing, Adhesion, Haptic materials