Our research thrust revolves around the interface of materials science and advanced manufacturing. We are particularly interested in understanding the fundamental processing-structure-property relationships in advanced materials and integrating control over materials on multiple length scales (atomic, microstructural, architectural) through materials processing and additive manufacturing (or 3D printing), to eventually arrive at extreme properties. Specific research activities include, but are not limited to:  

• Additive manufacturing technologies including laser powder bed fusion (also called selective laser melting), laser-directed energy deposition, direct ink writing, and plasma arc additive manufacturing. 
• Highthroughput materials design through combinatorial additive manufacturing approach. 
• Design and fabrication of architected materials (e.g., cellular materials, heterogeneous composites, functionally graded materials) with engineered structures through multi-material additive manufacturing, thermoplastic forming, powder metallurgy, and electrochemical processing for structural and energy (electrocatalysts and battery) applications.
• Manufacturing and design of advanced structural materials (e.g., metallic glasses, high-entropy alloys, lightweight and high-strength steels, aerospace superalloys, refractory alloys, etc).  

Example: Additive manufacturing of 3D architected materials with unique mechanical performance. 

Architected materials are ubiquitous in nature and engineering materials alike. By delicately structuring the constituent materials, naturally occuring materials such as bone and sponge often achieve extraordinary mechanical efficiency, from which we learn lessons on design of engineering architected materials. Combining the structural design motif and the versatile additive manufacturing tools such as laser powder bed fusion and direct ink writing, a rich variety of lightweight architected materials made of metallic glases, crystalline metals, ceramics, graphene, polymers, and even multi-materials can be fabricated and optimized for target mechanical performance, for example, high elasticity, stiffness, strength, or damage tolerance.

Example: Additive manufacturing of 3D hierarchical metal electrochemical catalyst with high surface area and rapid mass transport. 
Nanoporous metals are ideal electrochemical catalysts by offering both large surface area and high electrical conductivity. However, the slow mass transport kinetics within monolithic nanoporous metals often prevents scalable electrochemical applications. Using direct ink writing based additive manufacturing combined with chemical dealloying, 3D hierarchical metal catalysts with digitally controlled macroarchitectures (mm~cm) and nanoporous network structures (nm) can be achieved to increase and direct the mass transport while maintaining the high specific surface area. This approach can be applied to a variety of metal and alloy (e.g., Au-Ag, Mn-Ni, Mn-Cu) systems to revolutionize the design of electrochemical plants.

Example: Additive manufacturing of hierarchical metals with high strength and ductility.
Traditional metallurgical approaches to strengthening of crystalline metals often come at the expense of ductility. Using laser-based additive manufacturing, materials with unprecedented strength and ductility can be achieved due to the unique and highly non-equilibrium microstructure upon repeated and rapid solidification. During layer-by-layer builds, for example, additively manufactured metals such as 316L steels and high-entropy alloys often demonstrate hierarchically heterogeneous microstructures with length scales spanning nearly six orders of magnitude, including chemical segregations and precipitates, dislocations, solidification cellular structures, low-angle grain boundaries, and tortuous high angle grain boundaries that deliver high strength and steady work-hardening and hence break the strength-ductility trade-off in conventional materials.

Example: Understanding the mechanical behavior of metallic glasses (MGs).
?Whereas MGs possess high strengths, their fracture or damage tolerance behavior varies dramatically among different chemical compositions or different structural states (within the same composition). Using thermoplastic forming, MGs fracture toughness test samples can be precisely fabricated with well-controlled metastable state under reproducible processing conditions, which allows systematic study of composition-microstructure-(fracture) property-processing relationships in MGs.