Multifunctional Cellular Solids

Nanotechnology has enabled the engineering of materials with improved physical properties, but these engineered systems lack the complex functionalities common in natural materials (like self-healing bone fractures). The Pikul Research Group group seeks to develop multifunctional nanoscale materials systems utilizing modern engineering and design principles to achieve mechanical and chemical properties not available in natural or man-made materials.

High strength inverse opal based cellular solids:

In this work, we fabricated nickel and rhenium nanocomposite inverse opal cellular solids with controllable specific moduli between 4 and 20 GPa / (Mg/m3) and specific strengths up to 230 MPa / (Mg/m3), which is greater than most high strength alloys including 4143 steel and Ti-6Al-4V. The nanoscale confinement of the strut diameter provides up to a 5X increase in the nickel strength over the bulk electrodeposited nickel. The inverse opal cellular solids were fabricated over 2 cm2 areas and made flexible or rigid based on the underlying substrate. The combination of self-assembly and near room temperature electrodeposition allow for scalable fabrication of the cellular solids with high specific strength and down to 10 nm control of structure and chemistry.

Figure 1
Figure 1: (a) The fabrication process for a unit cell of the cellular solid. (b)-(g) Cross section SEM images of nickel cellular solids used for mechanical testing. (b)-(c) A nickel inverse opal with no coating. (d)-(e) A nickel inverse opal with 19 nm of additional nickel electrodeposited. f) A nickel inverse opal with 25 nm of additional rhenium-nickel electrodeposited. (g) A closer image of one of the struts in (f). (h) A 2 cm2 nickel cellular solid with 500 nm pores and 15 µm thickness grown on a gold/chromium coated glass slide. (i) A nickel cellular solid with 300 nm pores grown on gold/chromium coated 20 µm thick polyimide.

The strut size, solids volume fraction, and chemistry of inverse opal cellular solids can be tuned to control the specific modulus and specific strength. When compared to other engineered materials, nickel inverse opal cellular solids provide a unique combination of moderate specific stiffness similar to natural structural materials and high specific strengths greater than most engineering alloys.

Figure 3: An Ashby plot comparing the specific modulus and specific strength of the nanoporous nickel cellular solids with nickel coating (orange) and rhenium coating (red) to other high strength materials. Natural materials are shown in green. Bulk electrodeposited nickel is shown in blue. Common Ti, Al, Ni, and Fe high strength alloys are labeled 1 – 8: 1 – CP Ti, 2 – 2024-T4, 3 – Inconel 718, 4 – 4143 steel, 5 – 7075-T6, 6 – HSSS steel, 7 – Ti-6Al-4V, 8 – Ti-10V-2Fe-3Al.


[1] James H. Pikul, Sezer Ozerinc, Runyu Zhang, Paul V. Braun, and William P. King, “Micro architected porous material with high strength and controllable stiffness”, IEEE Micro Electro Mechanical Systems Conference 2016, Shanghai.