Chen Group Statement of Research

We are interested in nanostructured biomaterials and nanophotonics for biomedical engineering applications. We investigate not only the fundamental scientific issues, such as cell interactions with nano-environments, nanomaterials synthesis, and nanoscale optics and thermal/fluid transport, but also the potential applications for medicine and the life sciences.

1. Biomaterials and Biomanufacturing:

Biomaterials – particularly biodegradable polymers – comprise a rapidly evolving set of medical technologies with numerous applications. While medical implants made of metals or glass would permanently remain in the biological tissue if not removed surgically, biomedical nano/micro-devices made of biodegradable polymers would naturally degrade and disappear in tissue over a desired period of time, eliminating the need for an additional surgery for implant removal. As a leading research team in this area, we have been developing laser and UV light based processing techniques, including laser direct ablation, laser melting, UV nanoimprinting, and stereolithography for biomaterials. We also investigate the mechanical, chemical and biological properties of such biomaterials and explore cell-material interactions through experiments and simulation. We have been creating 3D biomaterials with gradient of stiffness, Poisson’s ratio, geometry, size, and growth factor. Our targeted applications are drug delivery, nerve repair, and tissue regeneration.

Figure 1: (Left) 3D Scaffolds with designer shapes fabricated by DMD-based projection printing (DMD-PP), (middle) Nano-scaffold made by femtosecond laser direct-write, (right) auxetic scaffold with a negative Poisson’s ratio.

D. Y. Fozdar, P. Soman, J. W. Lee, L.-H. Han, S.C. Chen, “Three-dimensional Polymer Constructs Exhibiting a Tunable Negative Poisson's Ratio”, Advanced Functional Materials, Vol. 21 (No. 14), pp. 2712–2720, 2011.
W. Zhang and S.C. Chen, “Femtosecond Laser Nanofabrication of Hydrogel Biomaterial, MRS Bulletin, Vol. 36, pp. 1028-1032, December 2011.
S. Suri, L.H. Han, W. Zhang, A. Singh, S.C. Chen, C. E. Schmidt, “Solid Freeform Fabrication of Designer Scaffolds of Hyaluronic Acid for Tissue Engineering”, Biomedical Microdevices, Vol. 13 (6), pp. 983-993, 2011.

2. Nano/Micro-scale Tissue Engineering:

Our research in functionalized biomaterials provides enhanced knowledge of cell-material interactions at nano and microscales in response to integrated physical and chemical stimuli. The breadth of our focus spans the full range of physical dimensions (from nano- to micro- to meso-scale), time span (from femtoseconds to days), and biological dimensions (from molecular to cellular to tissue).

We are developing 3D nano/micro-structures to study cardiac cell interactions within 2D and 3D microenvironments with nanoscale control of growth factors and topographic guidance. This work will shed insight into the effects of external signals on biological events involved in development and tissue regeneration, and could provide insight into the desirable characteristics for therapeutic systems to aid cardiac tissue repair and regeneration.

In stem cell engineering, we are developing 3D scaffolds with nanotextures to study stem cell behavior in such 3D nano-environments. Through precise control of spatial and temporal distributions of biological factors in 3D scaffolds, we are also investigating the interactions of stem cells with extracellular matrix (ECM) proteins at the nanometer length scale, with the ultimate aim of creating advanced, clinically translatable biomimetic scaffolds. Our goal is to repair tissue defects resulting from cancer, trauma, congenital abnormalities, and infections.

Figure 2: (Left) Immunofluorescence images showing the biological functionality of the HUVEC seeded scaffolds. (Right) human mesenchymal stem cells seeded on a single-layer PEG scaffold with a zero Poisson’s ratio.

R. Gauvin, Y.-C. Chen, J. W. Lee, P. Soman, P. Zorlutuna, J. Nichol, S.C. Chen and A. Khademhosseini, “Microfabrication of complex porous tissue engineering scaffolds using 3D projection stereolithography,” Biomaterials, Vol. 33 (no.15), pp. 3824-3834, 2012.
P. Soman, D. Fozdar, J. W. Lee, A. Phadke, S. Varghese and S.C. Chen, “Three-dimensional Polymer Constructs Exhibiting a Zero Poisson’s Ratio”, Soft Matter, Vol. 8 (18), pp. 4946-4951, 2012.

3. Nanomaterials and Nanomanufacturing

Nanofabrication represents the essential steps in producing a nano-device or nanosystem. We have developed a set of novel, massively parallel nano-patterning techniques including: a) Surface Plasmons Assisted Nanolithography (SPAN); b) Digital Micro-mirror Device based Projection Printing (DMD-PP); c) Nanofabrication using Near-Field Laser optics (Nano-NFL); and d) Flash Imprint Lithography using a Mask Aligner (FILM). Our continued efforts in developing novel nanofabrication techniques include approaches that integrate top-down with bottom-up processes. Our aim is to apply these processes for the development of innovative biomedical devices for applications in medicine and the life sciences.

Figure 3: (Left) Nanoimprinting of hydrogel. (Right) PEG-coated gold nano-rods

D. Y. Fozdar, J. Lee, C. E. Schmidt, S.C. Chen, “Selective Axonal Growth of Embryonic Hippocampal Neurons to Competing Topographical Features of Various Size and Shape”, International Journal of Nanomedicine, Vol. 2011 (No. 6), pp. 45-57, 2010.
S. M. Wu, L. H. Han, S. C. Chen, “Three Dimensional Selective Growth of Nanoparticles on a Polymer Microstructure”, Nanotechnology, Vol. 20, pp. 285312 (1-4), 2009.

4. Nanophotonics and Metamaterials

Metamaterials are novel composites with artificial “atoms” and “molecules” that offer unique functionalities that never exist naturally. The “atoms” and “molecules” in metamaterials can be tailored in shape and size, the lattice constant and inter-atomic interaction can be precisely tuned, and “defects” can be designed and placed at desired locations. Such metamaterials could result in powerful new ways to probe, interrogate, and modify biological systems, from new high information-content intracellular probes to new strategies for disease diagnosis and therapeutics. Our current focus in metamaterials is nanophotonics to generate and manipulate light at the nanoscale, targeting applications in sensing, imaging, and gene regulation of biological systems. Novel cellular and molecular imaging techniques are essential to the advancement of fundamental biological research, as well as applied biomedical diagnostics.

Figure 4: (Left) Direct-write 3D metamaterials using plasmonic nanolithography. (Right) Tunable plasmonic superlens for subwavelength imaging

A. Battula and S. C. Chen, “Tunable Plasmonic-Crystal Superlens for Subwavelength Imaging”, Physical Review B, Vol. 76 (no.19), pp. 193408 (1-4), 2007.
D.B. Shao and S.C. Chen, “Direct Patterning of Three-dimensional Periodic Nanostructures by Surface-Plasmon-Assisted Nanolithography”, Nano Letters, Vol. 6 (10), pp. 2279-2283, 2006.