Micro/nano-structured materials possess exclusive thermal, electrical, mechanical, and surface properties that are crucial for many important applications, such as thermal management, electrochemical energy storage and conversion, high-strength and lightweight structures, sensors, and drug delivery carriers. In order to effectively utilize these materials, advanced methods need to be developed for large-scale fabrication and integration with meso/macro scale systems. While fabrication of micro/nano-structured materials requires fundamental understanding of materials behavior at the atomic scale, translating laboratory results into large-scale applications also presents a substantial challenge. The goal of our research effort is to establish a world-renowned program that will not only foster scientific discovery, but also promote real world problem solving in the area of micro and nano-manufacturing.


Solid State Foaming

The inherent advantage of solid-state foaming is the ability to control the foam morphology by varying the process parameters. This allows us to vary the pore size and porosity as per the needs of the intended application. Even though these foams exhibit good properties such as low thermal conductivity that are favorable for certain applications, they suffer from low electrical conductivity and poor ablative performance restricting their usage for other applications. One possible solution to overcome this shortcoming is to add nano particles to enhance the desired property of the foam. A variety of polymers including bio-compatible/degradable polymers could be processed using this technique. On the experimental front this involves material processing techniques such as solid state foaming, compounding, injection molding, inverse molding, solvent casting, and additive manufacturing. Computational studies involve developing models using Monte Carlo methods, molecular dynamics and finite element analysis to predict the properties of these foams as a function of nano particle loading, pore size and porosity. These models would serve as a design tool to determine the foam morphology based on the requirements of the desired application.


Process Outline

The goal of this research project is to fabricate extracorporeal bio-artificial organ systems utilizing three dimensional (3D) tissue scaffolds that will assist in organ transplantation. This project extends on the work currently being performed in our research group on fabrication of 3D tissue scaffolds for biomedical applications. 3D tissue scaffolds can be used to grow cells and replicate the functioning of the tissues in the human body. However, the major challenge in the fabrication of large scale 3D tissue scaffolds is the need to have highly porous and interconnected scaffolds with desired mechanical properties to allow for cell growth and proliferation. In this study, multiple approaches to fabricate tissue scaffolds with dual pore networks will be evaluated. These include combined 3D printing and solid state foaming, leaching of 3D printed scaffolds, and laser foaming of 3D printed structures. Scaffolds need to have dual pore networks to ensure that there are separate passage ways for flow of nutrients and waste respectively. These scaffolds with desired properties will be incorporated into bioreactor chambers integrated with sensors and fluidic networks resulting in extracorporeal bio-artificial organs. The bioreactor chamber will work in conjunction with fluidic networks to circulate nutrients and drugs and remove waste.


Vacuum FiltrationParticle assembly processes using polymer or silica spheres offer the capability of fabricating close-packed highly ordered structures. These opal structures could then be used as templates to fabricate polymer, metal (nickel) and ceramic foams. This technique provides a method of processing materials with small feature sizes that otherwise cannot be processed. Apart from the experimental work, computational efforts are focused on investigating permeability and fluid flow in the porous structure.


Porous surface of polymer nanofoamsPolymer nanofoams with pore sizes less than 10 nm can be used for highly selective gas separations in the petrochemical industry reducing overall costs. Solid-state foaming has potential to be employed to fabricate nanostructured open celled foams with pore size less than 10 nm. The experimental work is focused on determining critical gas sorption and foaming conditions to reduce the pore size down to 10 nm and fabricate skinless open celled nano foams.