Project Overview: Stimuli-responsive materials have gained significant interest in the last decades, as they possess exclusive static and dynamic controllable properties. A new class of these materials known as magnetoactive elastomers (MAEs) are composed of mag
netic particles embedded in an elastomer. Functional behaviors of MAEs like actuation, shape memory effect, sensing, etc. make them promising candidates for various applications such as soft robotics, biomedical devices, reconfigurable structures, actuators, etc. Our research is motivated by the medical device industry need for better fitting, patient-specific devices. We have identified two applications: pediatric non-invasive (NIV) nasal cannulas and masks. As illustrated in Figure 1, nasal cannulas are utilized to offer additional oxygen to newborns with underdeveloped lungs. While these cannulas are less invasive than face masks, they can cause tissue damage to the inner nasal cavities. As a solution, a smart nasal prong device composed of magnetoactive elastomer is suggested, which can alter its shape from circular to elliptical or hourglass shapes to reduce tissue trauma. To address this need, we can design an iron oxide-loaded epoxy MAE. However, there are multiple factors that control the final properties of MAE such as the type of materials, magnetic particle-elastomer interaction, magnetic particle alignment, and processing conditions that should be optimized.
The first step in this research project is to increase the actuation ability of MAEs, which is controlled by the saturation magne tization (Ms) of MAEs. To actuate MAEs we apply a magnetic field on the sample. Based on the magnetic particles’ dipole alignment different levels of actuation occur. So, by enhancing iron oxide distribution and alignment through the magnetic field, the MAEs undergo a higher level of actuation. However, due to the high surface charge of iron oxide particles, rapid agglomeration happens after dispersing them in a polymer melt, resulting in Ms reduction. Hence improving the dispersion of iron oxide particles is essential in terms of Ms optimization. We hypothesize that enhancing the iron oxide-epoxy interaction not only leads to dispersion improvements but also increases Ms. Based on the Hildebrand-Scott solubility theory, we found that coating Polyethylene glycol on the surface of particles can improve the interaction between iron oxide-epoxy.
Background and Motivation: In recent years, the development of smart materials has been a focus of interest for biomedical deviceinnovations. Specifically, MAEs have demonstrated potential in biomedical and soft robotic applications due to their remarkable stimuli-responsivity. One of the key advantages of smart materials is their actuation capabilities without the need for direct contact, which is particularly appealing for many applications. Customization of medical devices is of utmost importance, and the incorporation of MAEs into implants can save patients from undergoing a second surgery. The use of an induction device to trigger the shape recovery of MAEs allows for the adjustment of mechanical properties without incisions to the body, providing a safer and more efficient option for patients. Overall, the development of smart materials has opened exciting possibilities for creating customizable biomedical devices. Further research and studies are being conducted to improve the design and functionality of these devices, and it is expected that these advances will lead to significant improvements in the treatment of patients.
We suggest creating and using additive manufacturing (AM) to produce smart devices that can change their shape as per the patient’s changing requirements. To make this process efficient and quick, the shape adaptation features should be automatically customized based on a set of design requirements. It would be best to manufacture the entire device as an integrated component on a single AM machine, without requiring inserts or conventionally fabricated components. The two primary research aims are:
- Design and fabricate test coupons of magneto-active elastomers (MAE); assess the effect of polyethylene glycol coatings on active properties, dispersity of iron oxide, saturation magnetization, and reproducibility.
- Investigate the effect of additives and time on viscosity/printability, and then optimize the additives concentration and processing variables in terms of printability
Research Overview: The proposed research will be led on two fronts. First, the effect of iron oxide surface treatment by polyethylene glycol on particle dispersion will be evaluated using scanning electron microscopy (SEM). It is expected that the addition of polyethylene glycol to the system enhances the iron oxide dispersion. Also, to obtain the Ms of each sample vibrating sample magnetometry (VSM) should be conducted. We anticipate that higher concentrations of polyethylene glycol on the iron oxide particles increase the Ms of the samples. Second, we will study the rheological properties of the MAEs’ slurries. As we suggested using AM for MAEs fabrication, a rheological study will help us to understand the behavior of slurries during printing. In this regard, using a viscometer we will obtain the shear stress vs. shear rate curves, which are helpful to determine viscosity shear rate-dependency. We believe that these slurries are shear-thin. Moreover, dynamic rheological characterization will be conducted as finding the gel point of the slurries, at which the storage modulus (G´) is equal to the lose modulus (G´´), is important in terms of printing shear rate. This reveals the optimum shear rate at which slurries show good printability with liquid-like behavior (G´´> G´).
Outcomes and Relevance: To make customized devices with active materials possible, they must be designed specifically for the AM process and its limitations, so that functional parts can be created on the first attempt without the need for expensive and time-consuming rework. We aim to optimize the concentration of components as well as the functionality of iron oxide particles in terms of Ms enhancement and printability. We will print active materials to produce multimaterial smart devices in a single AM process and customize each device using a computationally efficient inverse design approach to ensure that they are manufacturable.