3D nanometer-thin membrane borrows from biology

Mimicking the structure of the kidney, a team of scientists from Lawrence Livermore National Laboratory (LLNL) and the University of Illinois at Chicago (UIC) have created a three-dimensional nanometer (nm)-thin membrane that breaks the permeance-selectivity trade-off of artificial membranes.

Highly permeable and selective membranes are useful for a wide range of applications, such as dialysis, water purification and energy storage. However, conventional synthetic membranes based on two-dimensional structures suffer from the trade-off limitation between permeability and selectivity, arising from their intrinsically limited surface area and long complex pore geometries.

Taking a cue from biological systems that achieve a highly selective and rapid trans-membrane mass transport by employing efficient 3D functional structures, the team developed a self-supportive 3D membrane composed of two 3D interconnected channels, which are separated by a nanometer-thin porous titanium-oxide (TiO₂) layer.

This unique biomimetic 3D architecture dramatically increases the surface area, and thus the filtration area, by 6,000 times, coupled with an ultra-short diffusion distance through the 2-4-nm-thin selective layer. These features provide the 3D membrane's high separation performance with fast mass-transfer characteristics.

“Our study suggests that the 3D membrane design has great potential for overcoming the limitations of conventional synthetic membranes” said LLNL materials scientist Jianchao Ye, one of the corresponding authors of a paper appearing in the journal Materials Horizons.

“The results of this work also provide fundamental design criteria for the development of high-performance nanoporous membranes,” said Sangil Kim, former LLNL scientist now at the University of Illinois at Chicago.

The team said the new 3D membrane exhibits promising applications in biomedical engineering and the energy storage area, such as membranes for lithium-sulfide and lithium-oxide batteries.

“The 3D biomimetic membrane design demonstrated in this work will ultimately enable the development of high-performance implantable hemodialysis systems and artificial membrane lungs, thus changing the life of hundreds of thousands of Americans with total and permanent kidney failure and lung failure,” LLNL scientist and co-author Juergen Biener said.

The team also pointed out that the performance can be further improved by geometrical optimizations using 3D printing and machine learning techniques, which leads to tremendous research opportunities in the membrane field.

Other LLNL scientists include Siwei Liang, Zhen Qi, Monika Biener, Thomas Voisin, Joshua Hammons, Ich Tran, Marcus Worsley, Tom Braun, Morris Wang and Theodore Baumann. Doctoral  student Tongshuai Wang (a former LLNL summer intern) from the University of Illinois at Chicago contributed to the membrane performance tests.

The research was funded by the Laboratory Directed Research and Development program, Institutional Scientific Capability Portfolio program and the National Science Foundation.