Materials engineers face various tasks that require multidisciplinary approaches to solve specific problems. While every task of a materials engineer must prioritize the performance of the overall system with a careful concerns on economic perspective, problem solving requires deep understanding of chemistry, physics, and other engineering disciplines including mechanical, electrical, and chemical. In my research group at the Univ. of Alberta, we solve problems related to soft materials with high toughness, such as gels, elastomers, and textiles. These materials can accommodate extensive dimensional changes during operation, and thus are often employed in the wearable devices and medical instruments, along with many other engineering applications. In this presentation, I tell two anecdotes to showcase how material engineers collaborate with chemistry researchers to solve problems.
The first example is related to the development of ex-vivo heart perfusion (EVHP) device for heart transplant. EVHP) is an innovative technology in which a donor heart is kept alive and beating outside of the human body. During EVHP, the organ is kept near body temperature (37 °C) and perfusate (enriched blood) flows through the heart chambers, simulating physiological conditions. Currently, overly stiff tubing used in EVHP devices causes premature pressure wave reflection during heartbeat, which can increase risk of donor organ rejection. Use of aorta-inspired compliant tubing for EVHP devices, namely, RTV silicone elastomer tubes ‘jacketed’ by a sleeve of knitted fabric, was hypothesized to potentially mitigate this problem. We used a custom-built flow loop to pump fluid into sections of compliant tubing at known pressures and measured the response; our main finding was that the tubes deform rapidly as pressure initially increases, but eventually display ‘self-regulation’ behavior where their continued distension is tempered by the stiffening of fibres in the fabric. The experimental findings were supported by our 3-dimensional finite element simulations in ABAQUS using material coefficients obtained from uniaxial tensile tests of the tubing materials.
In the second example, methodologies from polymer physics are utilized to elucidate the phase behavior of water in hydrogels, specifically the behavior of water molecules in polyampholyte gel matrix at low temperature conditions as low as –56 °C. Here, small- and wide-angle x-ray scattering (SAXS and WAXS), low-dose field-emission SEM (FE-SEM), scanning transmission electron microscopy (STEM), differential scanning calorimetry (DSC), and 1H and 2H solid- state neutron magnetic resonance (NMR) are used to understand the enhanced ionic conduction at the ice-forming temperature ranges. Based on the understanding, we demonstrate the use of the hydrogel as a gel polymer electrolyte for low-temperature applications. We also showcase the polyampholyte hydrogel’s applications in thermally sensitive smart windows (by harnessing upper critical solution temperature (UCST) nature of the hydrogel’s phase behaviour) and in electronic skins (by harnessing the electrically conductive nature of the salt-containing hydrogel).