In-Mold Assembly of Multi-Functional Structures

Combining the recent advances in injection moldable polymer composites with the multi-material molding techniques enable fabrication of multi-functional structures to serve multiple functions (e.g., carry load, support motion, dissipate heat, store energy). Current in-mold assembly methods, however, cannot be simply scaled to create structures with miniature features, as the process conditions and the assembly failure modes change with the feature size. This dissertation identifies and addresses the issues associated with the in-mold assembly of multi-functional structures with miniature components. First, the functional capability of embedding actuators is developed. As a part of this effort, computational modeling methods are developed to assess the functionality of the structure with respect to the material properties, process parameters and the heat source. Using these models, the effective material thermal conductivity required to dissipate the heat generated by the embedded small scale actuator is identified. Also, the influence of the fiber orientation on the heat dissipation performance is characterized. Finally, models for integrated product and process design are presented to ensure the miniature actuator survivability during embedding process. The second functional capability developed as a part of this dissertation is the in-mold assembly of multi-material structures capable of motion and load transfer, such as mechanisms with compliant hinges. The necessary hinge and link design features are identified. The shapes and orientations of these features are analyzed with respect to their functionality, mutual dependencies, and the process cost. The parametric model of the interface design is developed. This model is used to minimize both the final assembly weight and the mold complexity as the process cost measure. Also, to minimize the manufacturing waste and the risk of assembly failure due to unbalanced mold filling, the design optimization of runner systems used in multi-cavity molds for in-mold assembly is developed. The complete optimization model is characterized and formulated. The best method to solve the runner optimization problem is identified. To demonstrate the applicability of the tools developed in this dissertation towards the miniaturization of robotic devices, a case study of a novel miniature air vehicle drive mechanism is presented

Recent trends, technical concepts and components of computer-assisted orthopedic surgery systems: A comprehensive review

Computer-assisted orthopedic surgery (CAOS) systems have become one of the most important and challenging types of system in clinical orthopedics, as they enable precise treatment of musculoskeletal diseases, employing modern clinical navigation systems and surgical tools. This paper brings a comprehensive review of recent trends and possibilities of CAOS systems. There are three types of the surgical planning systems, including: systems based on the volumetric images (computer tomography (CT), magnetic resonance imaging (MRI) or ultrasound images), further systems utilize either 2D or 3D fluoroscopic images, and the last one utilizes the kinetic information about the joints and morphological information about the target bones. This complex review is focused on three fundamental aspects of CAOS systems: their essential components, types of CAOS systems, and mechanical tools used in CAOS systems. In this review, we also outline the possibilities for using ultrasound computer-assisted orthopedic surgery (UCAOS) systems as an alternative to conventionally used CAOS systems.Web of Science1923art. no. 519

4D Microprinting Based on Liquid Crystalline Elastomers

Two-photon laser printing (2PLP) is a disruptive three-dimensional (3D) printing technique that can afford structural fabrication at the submicrometer scale. Apart from constructing static 3D structures, research in fabricating dynamic ones, known as "4D printing”, is becoming a burgeoning field. 4D printed structures exhibit adaptability or tunability towards their environment through the control of an external stimulus. In contrast to the rapid growth in macroscale fabrication, progress in microprinted actuators has only been scarcely reported. Liquid crystal elastomer (LCE) stands out among the promising classes of smart materials for fabricating microrobotics or microactuators due to its distinct anisotropic property, which enables the printed structures to exhibit automated reversible movements upon exposure to stimuli without environmental limitations. Nevertheless, the use of 2PLP for the manufacture of 4D printed LCE microstructures with high versatility and complexity have presented some challenges, limiting their implementation in final applications. This thesis aims to overcome two main obstacles faced in this regard: first, the limitation of two-photon printable stimuli-responsive materials; and second, the lack of a facile approach for aligning liquid crystal (LC) within three dimensions. The first part of this thesis aims on expanding the library of materials used for implementing light responsiveness into LC microstructures, as light provides a higher degree of temporal and spatial control compared to other stimuli. The initial approach has involved incorporation of acrylate-functionalized photoresponsive molecules, such as azobenzene and the donor-acceptor Stenhouse adduct (DASA), into a LC ink using a conventional synthetic method. However, several challenges, such as compatibility with the LC ink, have prevented the achievement of 4D printing via 2PLP. The second approach is based on post-modifying printed LC structures and successfully fabricated microactuators with five different photoresponsive features by individually incorporating each light-absorbing molecule. Furthermore, LC microactuators that exhibit distinct actuation patterns under different colors of light were fabricated by simultaneously implementing orthogonal photoresponsive molecules. The second project presented in this thesis focuses on developing a new strategy to induce alignment domains in a more flexible manner, with the aim of spatially tailoring the LC topology of the 3D printed microstructures. This is achieved by microprinting 3D scaffolds based on polydimethylsiloxane (PDMS) to manipulate the alignment directions of LC molecules. Taking advantage of 2PLP to fabricate arbitrary scaffolds, LC alignments, including planar and radial patterns, could be introduced freely and simultaneously in three-dimensional space with varying degrees of complexity. The applicability of this alignment approach was demonstrated by fabricating responsive LC microstructures within different PDMS environments, and distinct actuation patterns were observed. Overall, these two breakthroughs have unveiled a wide array of new potentials for the utilization of responsive LC microsystems with tunable functionalities and customizable actuation responses, that can be applied across various domains and applications

Technology 2001: The Second National Technology Transfer Conference and Exposition, volume 2

Proceedings of the workshop are presented. The mission of the conference was to transfer advanced technologies developed by the Federal government, its contractors, and other high-tech organizations to U.S. industries for their use in developing new or improved products and processes. Volume two presents papers on the following topics: materials science, robotics, test and measurement, advanced manufacturing, artificial intelligence, biotechnology, electronics, and software engineering

12th EASN International Conference on "Innovation in Aviation & Space for opening New Horizons"

Epoxy resins show a combination of thermal stability, good mechanical performance, and durability, which make these materials suitable for many applications in the Aerospace industry. Different types of curing agents can be utilized for curing epoxy systems. The use of aliphatic amines as curing agent is preferable over the toxic aromatic ones, though their incorporation increases the flammability of the resin. Recently, we have developed different hybrid strategies, where the sol-gel technique has been exploited in combination with two DOPO-based flame retardants and other synergists or the use of humic acid and ammonium polyphosphate to achieve non-dripping V-0 classification in UL 94 vertical flame spread tests, with low phosphorous loadings (e.g., 1-2 wt%). These strategies improved the flame retardancy of the epoxy matrix, without any detrimental impact on the mechanical and thermal properties of the composites. Finally, the formation of a hybrid silica-epoxy network accounted for the establishment of tailored interphases, due to a better dispersion of more polar additives in the hydrophobic resin

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018