James S. Oakdale

Printable enzyme-embedded materials for methane to methanol conversion

An industrial process for the selective activation of methane under mild conditions would be highly valuable for controlling emissions to the environment and for utilizing vast new sources of natural gas. The only selective catalysts for methane activation and conversion to methanol under mild conditions are methane monooxygenases (MMOs) found in methanotrophic bacteria; however, these enzymes are not amenable to standard enzyme immobilization approaches. Using particulate methane monooxygenase (pMMO), we create a biocatalytic polymer material that converts methane to methanol. We demonstrate embedding the material within a silicone lattice to create mechanically robust, gas-permeable membranes, and direct printing of micron-scale structures with controlled geometry. Remarkably, the enzymes retain up to 100% activity in the polymer construct. The printed enzyme-embedded polymer motif is highly flexible for future development and should be useful in a wide range of applications, especially those involving gas–liquid reactions.

Post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon lithography [A post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon polymerization]

Two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.

Microencapsulation of advanced solvents for carbon capture

Purpose-designed, water-lean solvents have been developed to improve the energy efficiency of CO2 capture from power plants, including CO2-binding organic liquids (CO2BOLs) and ionic liquids (ILs). Many of these solvents are highly viscous or change phases, posing challenges for conventional process equipment. Such problems can be overcome by encapsulation. Micro-Encapsulated CO2 Sorbents (MECS) consist of a CO2-absorbing solvent or slurry encased in spherical, CO2-permeable polymer shells. The resulting capsules have diameters in the range of 100-600 μm, greatly increasing the surface area and CO2 absorption rate of the encapsulated solvent. Encapsulating these new solvents requires careful selection of shell materials and fabrication techniques. We find several common classes of polymers are not compatible with MECS production, but we develop two custom formulations, a silicone and an acrylate, that show promise for encapsulating water-lean solvents. We make the first demonstration of an encapsulated IL for CO2 capture. The rate of CO2 absorption is enhanced by a factor of 3.5 compared to a liquid film, a value that can be improved by further development of shell materials and fabrication techniques.

Additive manufacturing of complex micro-architected graphene aerogels

3D graphene foams exhibit immense degradation of mechanical properties. Micro-architecture can alleviate this problem, but no current technique meets the manufacturing requirements. Herein we developed a light-based 3D printing process to create hierarchical graphene structures with arbitrary complexity and order-of-magnitude finer features, showing enhanced mechanical properties at decreasing density.

Enzyme-Embedded, Microstructural Reactors for Industrial Biocatalysis

In this project we explored enzyme-catalyzed methane conversion to methanol. Industrial biological approaches to methane conversion using whole organisms are predicted to be more energy efficient than chemical approaches, but are limited by mass transfer of the gas phase reactants, methane and oxygen, to the organisms. We demonstrated that 3D printing the enzyme particulate Methane Mono Oxygenase (pMMO) embedded in a polymer can improve the kinetics of methane to methanol conversion. This improvement was likely due to the ability to increase the surface area of the catalytic material using 3D printing. We also demonstrated the first continuous use of pMMO in a flow-through reactor. In order to understand the fundamental kinetic properties of pMMO, we conducted an in-depth study of pMMO kinetics using analytical tools developed in our lab. Finally, we developed a new copolymer system that allowed tuning of the gas permeability of the biocatalytic material.