Dr. SungWoo Nam’s research program at the University of Illinois at Urbana-Champaign (UIUC) is focused on Multifunctional Engineered Nanomaterials and Devices. In particular, his laboratory focuses on nano-engineering graphene and 2-dimensional materials based nanostructures and devices for multifunctionality.

1. Mechanically-driven Nano-manufacturing:

This aspect of Nam’s research program is anchored by nanoscale materials fabrication and processing. In particular, Nam’s research group is interested in –

  1. Investigating new and manufacturable fabrication methods of graphene and 2-dimensional (2D) materials
  2. Exploring mechanically-driven self-assembly of graphene and 2D materials for advanced micro- and meso-scale meta-materials and structures
  3. Processing micro-/meso-scale structures for advanced devices and sensors

Nam’s research group has demonstrated a facile, robust, and controllable approach to assembling and densifying a parallel array of nanowires using shrinkable shape memory polymers. Using thermal-induced shrinkage of polystyrene, his research group was able to successfully assemble and densify nanowires arrays up to close-packing and, furthermore, achieve tunable density by controlling the shrinkage process (Nano Letters 14, 3304 (2014)).

Furthermore, his research group has extended this innovative work toward the texturing of 2D materials. His research team has demonstrated that the systematic shrinkage of the underlying pre-strained thermoplastic substrate induces delamination and buckling of graphene, leading to 3-dimensional (3D) textured graphene surfaces. Uniform arrays of graphene crumples were created at the centimeter scale by controlling simple thermal processing parameters without compromising the superb electrical properties of graphene. Furthermore, his team demonstrated 3-dimensional crumpled graphene field-effect transistor arrays in a solution-gated configuration. This approach can also work with arbitrary 3D surfaces, a necessary prerequisite for adaptive electronics, and will enable facile large-scale topography engineering of not only graphene but also other thin-film and 2D materials. This work demonstrated the unique capability of strain and topography engineering of 2D materials (Nano Letters 15, 1829 (2015)).

More recently, his research group has demonstrated a robust approach to integrating graphene onto 3D microstructured surfaces while maintaining the structural integrity of graphene, where the out-of-plane dimensions of the 3D features vary from 3.5 to 50 μm. His team utilized substrate swelling, shrinking, and adaptation to achieve damage-free, large area integration of graphene on 3D microstructures. He also demonstrated the versatility of the approach by extension to a variety of 3D microstructured geometries. This work addresses the challenges associated with fractures from local stress during transfer onto three-dimensional microstructured surfaces, and will pave the way for 3D integration of 2D materials and expand potential realm of applications of graphene and 2D materials (Nano Letters 15, 4525 (2015)).

2. Fundamental Investigations on Surface Characteristics of Graphene and 2D Materials:

This aspect of Nam’s research program is directed toward understanding the surface energy and adhesion of graphene and 2D materials. In particular, the research advances our fundamental knowledge of underlying substrates and the effects of surface airborne contamination on graphene’s surface energy/adhesion.

Nam’s research group expands fundamental understandings of the wettability of graphene. His group investigated the intrinsic water contact angle (WCA) of multilayer graphene to explore different methods of cleaning multilayer graphene and evaluate the efficiency of those methods on the basis of spectroscopic analysis. In particular, Nam’s group has carried out comprehensive studies of various graphene surface treatments/cleaning methods to achieve low, intrinsic WCA, and demonstrated that such WCA is correlated with spectroscopic analysis. A WCA value of 45° was measured for a clean graphene surface, and X-ray photoelectron spectroscopy results revealed that the WCA value changed drastically depending on the amounts of oxygen-containing and hydrocarbon-containing groups on the surface. This work was the first to demonstrate semi-quantitative XPS analysis of graphene surface contamination and provide a platform to understand the wettability of graphene surfaces (Langmuir 30, 12827 (2014)).

3. Multifunctional Mechanical Meta-Materials and Sensor Devices:

Nam’s research group has been investigating mechanically-tunable materials and sensor devices by looking into potential applications of nano-engineered graphene and 2D nanostructures. In particular, his group has developed flexible and stretchable graphene photosensors and strain gauges based on crumpled graphene structures. Furthermore, hybrid structures of crumpled graphene and Au plasmonic nanoantenna are also investigated for high performance, 3D optical sensors. Nam’s research group is also investigating novel chemical and biosensor applications by bridging multifunctional nano-devices and biological systems to enable new opportunities for quantitative biology in their natural 3-dimensional (3D) forms. Related research efforts were published in Nano Letters 13, 2814 (2013) and Nature Materials 11, 120 (2012).