Abstract: My research is aimed at creating materials that will be the building blocks of economical, large-scale, clean energy technologies of the future. The key to creating effective energy conversion materials is controlling the flow of energy, matter and electricity at the nanoscale by careful design of the shape, size and composition of materials at the same scale. I am primarily interested in developing materials for cheap yet efficient solar cells that either generate electricity or directly generate chemical fuels. As an example, I will present semiconductor/liquid junction solar cells constructed on metal oxide nanowire scaffolds that achieved record photocurrents, and also new results on metal sulfide materials. Equally important is the development of methods for the rapid, economical synthesis of highly structured nanomaterials in quantities that match the scale of our energy problem. As an example, I will describe novel flame-synthesis methods for the bottom-up growth of arrays of single-crystal metal oxide nanowires and composites over large areas on electrically conductive substrates. Technologies like this may someday remove barriers to the practical implementation of nanotechnology in solar energy conversion devices.

Biographical Sketch: Pratap Rao is an Assistant Professor in the Mechanical Engineering Department at the Worcester Polytechnic Institute (WPI). He received his BS in 2007 from WPI and his PhD in 2013 from Stanford University. He has co-authored 27 peer-reviewed papers that have collectively been cited over 1,700 times. His work on materials for solar energy conversion and electrocatalysis is currently funded by the National Science Foundation and the Massachusetts Clean Energy Center. At WPI, he is the recipient of the Mechanical Engineering Excellence in Research Award and the James Nichols Heald Research Award.

 

Abstract: Research in the Simmons Lab works to understand the feedback loop between cell-level processes and tissue-level mechanics. We have developed our own characterization equipment to effectively compare excised tissues, synthetic hydrogels, and engineered constructs. With our custom tools and models, we are studying a novel animal, the African Spiny Mouse, that is capable of regenerating skin, cardiac muscle, and skeletal muscle without fibrosis, and we are attempting to recreate these regenerative processes in vitro. To study pancreatic cancer, we are using cells from patients to engineer tumors-in-a-dish that have the same mechanical properties of the original tumors for translational and clinical applications.

Biographical Sketch: Chelsey S. Simmons, Ph.D., joined the Department of Mechanical and Aerospace Engineering at the University of Florida in Fall 2013, following a visiting research position at the Swiss Federal Institute of Technology (ETH) Zurich. Her research lab investigates the relationship among cell biology and tissue mechanics, and their projects are funded by the National Science Foundation, National Institutes of Health, and American Heart Association. She has received numerous fellowships and awards, including BMES-CMBE’s Rising Star Award (2017) and ASME’s New Faces Award (2015). In addition to her engineering research and coursework, Simmons received a Ph.D. Minor in Education and is the PI of a $600k Research Experiences for Teachers Site. She teaches undergraduate Mechanics of Materials and graduate BioMEMS courses and received Teacher of the Year in 2017. Simmons received her B.S. cum laude from Harvard University and her M.S. and Ph.D. from Stanford University.

Join us to learn about the exciting research that some of our Faculty and their groups are doing at our Department at our ME Lightning Talks!  Pizza will be provided.  Since space is limited, this event is limited to ME graduate students and faculty, and a limited number of ME undergraduate seniors. If you are an undergraduate senior and would like to attend, please RSVP at https://goo.gl/forms/HypP70ShGSqKTNay2  (spots will be granted in the order that confirmations are received until capacity is filled). You will receive later in the week an email confirming your attendance.

 

Prof. Thanh Nguyen – Novel processing of biodegradable and biocompatible polymers at small scales for medical applications. Biodegradable polymers have a significant impact to medical field. In my talk, I will present researches which aim to further fabricate and process the polymers at small scales, enabling their special functions for use in important medical implant devices. The first part of this talk will be focused on a novel manufacturing technology, which allows to create versatile 3D microstructures of biodegradable polymers for vaccine/drug delivery. The second part of this talk will be emphasized on a new approach, which enables the polymers to be electromechanically-active for use in an implanted biodegradable force-sensor. The presented works, while significantly enhancing functionality and usefulness of the polymers, do not compromise their excellent biodegradability and biocompatibility for medical use.

 

Prof. Georgios Matheou – Numerical model error in simulations of turbulence. Although turbulent flows are prominent and ubiquitous in many applications, their prediction remains challenging. Simulation has the potential to become the primary tool for discovery by utilizing recent advances in computing power. Thus, high fidelity simulations with good characterization of model errors are required. A study of numerical model error in passive scalar mixing is discussed. The range of values of scalar fields in turbulent flows is bounded by their boundary values, for passive scalars, and by a combination of boundary values, reaction rates, phase changes, etc., for active scalars. In practice, this fundamental constraint is often violated with scalars exhibiting unphysical excursions. Analysis of scalar-excursion statistics shows that unphysical scalar excursions in large-eddy simulations result from dispersive errors of the convection-term discretization where the subgrid-scale model provides insufficient dissipation to produce a sufficiently smooth scalar field.

 

Prof. Dianyun Zhang – An Integrated Multi-Scale and Multi-Physics Modeling Tool for Advanced Composite Structures. Fiber-reinforced polymer matrix composites have been increasingly used in aerospace structures owing to the weight and life-cycle cost savings they provide. However, manufacturing these lightweight materials involves curing an epoxy resin under elevated temperatures, which inevitably results in dimensional change and residual stress build-up. To minimize these manufacturing-induced imperfections through an optimal cure cycle, it is critical to develop a physics-based process model underlying the fundamentals of resin curing kinetics and the correlation between the process parameters and the final structural performance. In this talk, an integrated multi-physics and multiscale model will be used to predict the residual stress generation and dimensional change of a composite laminate. Predictions of the warpage of an unsymmetrical panel and the spring-in angle of an L-shaped composite flange will be used to illustrate the advantages of the proposed modeling tool.

Abstract: Materials Genome Initiative (MGI) and Integrated Computational Materials Engineering (ICME) have the potential to accelerate discovery, developing, manufacturing, and deploying of advanced materials. However, it is usually not the material performance, but the structural performance or system performance we are pursuing. To fill the gap between materials genome and structural analysis, the concept of Structure Genome (SG) is proposed. SG is the smallest mathematical building block containing all the constitutive information for a structure. The Mechanics of Structure Genome (MSG) represents a revolutionary approach to multiscale modeling drastically different from the conventional bottom-up multiscale modeling approaches. The principle of minimum information loss (PMIL) is used to avoid a priori assumptions commonly invoked in other approaches. MSG confines all approximations to the constitutive modeling which can construct constitutive models for all types of structures including 3D solids, 2D plates/shells, and 1D beams, directly linking the structural properties with microstructural details. MSG simplifies multiscale constitutive modelling to answer three fundamental questions: 1) what is the original model needed for capturing relevant physics? 2) what is the model wanted for a particular design? 3) what is the SG? MSG allows one to choose the starting scale and ending scale and capture details as needed and affordable without invalid scale separation and assumptions within scales. A companion code called SwiftComp is developed as a general-purpose constitutive modeling software which can be used as a standalone code for virtual testing of structures and materials and as a plugin for conventional finite element software packages such as Abaqus, Ansys, Nastran with efficient high-fidelity composites modeling capabilities. SG concept is applicable to any structures and materials featuring heterogeneity and anisotropy including but not limited to composite materials, 3D printed materials, metamaterials, biomaterials, auxetic materials, smart materials, soft materials, etc.

Biographical Sketch: Dr. Wenbin Yu is a Professor in the School of Aeronautics and Astronautics at Purdue University after serving ten years as a faculty at Utah State University. He received his PhD in Aerospace Engineering from Georgia Tech and MS in Engineering Mechanics from Tsinghua University, China. He serves as Director for the Composites Design and Manufacturing HUB (cdmHUB.org), and Associate Director for the Composites Virtual Factory HUB (cvfHUB.org), and is the CTO for AnalySwift LLC (analyswift.com). His expertise is in micromechanics and structural mechanics with applications to composite/smart materials. He has developed several computer codes used today by thousands of researchers and engineers in government labs, universities, research institutes and companies. He is an ASME Fellow and AIAA Associate Fellow. He served as the chair for ASME Structures and Materials Technical Committee and currently serves as the vice chair for AIAA Materials Technical Committee. He serves on the editorial boards of two international journals.

Friday, November 11 • 2:30 PM – PWEB, Rm. 175

Reconfigurable Plasmonics and Metamaterials

Yongming Liu, Assistant Professor

Department of Mechanical and Industrial Engineering

Department of Electrical and Computer Engineering

Northeastern University, Boston, USA

Email: y.liu@neu.edu;

Group Website: http://www.northeastern.edu/liulab

Abstract: Plasmonics has become a very important branch in nano optics. It allows us to concentrate, guide, and manipulate light at the deep subwavelength scale, promising enhanced light-matter interaction, next-generation optical circuits, sub-diffraction-limited imaging, and ultrasensitive biomedical detection [1-3]. Furthermore, the assembly of judiciously designed metallic structures can be used to construct metamaterials and metasurfaces with exotic properties and functionalities, including anomalous refraction/reflection, strong chirality and invisibility cloak [4,5]. There is a pressing need of tunability and reconfigurability for plasmonics and metamaterials, in order to perform distinctive functionalities and miniaturize the device footprint. In this talk, I will present our recent work in reconfigurable plasmonics and metamateirals. First, I will discuss the first demonstration of reconfigurable plasmonic lenses operating in microfluidic environment, which can dynamically diverge, collimate and focus surface plasmons [6]. Second, I will present a novel graphene metasurface to fully control the phase and amplitude of infrared light with very high efficiency. It manifests broad applications in beam steering, biochemical sensing and adaptive optics in the crucial infrared wavelength range [7]. Finally, I will discuss origami-based, dual-band chiral metasurfaces at microwave frequencies. The flexibility in folding the metasurface provides another degree of freedom for geometry control in the third dimension, which induces strong chirality from the initial, 2D achiral structure [8]. These results open up a new avenue towards lightweight reconfigurable metadevices.

Biographical Sketch: Dr. Yongmin Liu obtained his Ph.D. from the University of California, Berkeley in 2009. He joined the faculty of Northeastern University at Boston in fall 2012 with a joint appointment in the Department of Mechanical & Industrial Engineering and the Department of Electrical & Computer Engineering. Dr. Liu’s research interests include nano optics, nanoscale materials and engineering, plasmonics, metamaterials, biophotonics, and nano optomechanics. He has authored and co-authored over 50 journal papers, including Science, Nature, Nature Nanotechnology, Nature Communications, Physical Review Letters and Nano Letters. Dr. Liu received Office of Naval Research Young Investigator Award (2016), 3M Non-Tenured Faculty Award (2016), Air Force Summer Faculty Fellowship (2015), and Chinese Government Award for Outstanding Students Abroad (2009). Currently he serves as an editorial board member for Scientific Reports, EPJ Applied Metamaterials and Nano Convergence.

References: [1] S. A. Maier, “Plasmonics: fundamentals and applications”, Springer Science+ Business Media (2007); [2] T. Zentgraf et al., Nature Nanotechnology 6, 151 (2011); [3] Y. M. Liu, et al., Nano Letters 12, 4853 (2012); [4] Y. M. Liu and X. Zhang, Chemical Society Reviews 40, 2494 (2011); [5] K. Yao and Y. M. Liu, Nanotechnology Review 3, 177 (2014); [6] C. L. Zhao et al., Nature Communications 4:2350 (2013); [7] Z. B. Li et al., Scientific Reports 5, 12423 (2015); [8] Z. Wang et al., manuscript in preparation.

For additional information, please contact Prof. Ying Li at (860) 486-7110, yingli@engr.uconn.edu or

Laurie Hockla at (860) 486-2189, hockla@engr.uconn.edu

Friday, September 9 • 2:30 PM – PWEB, Rm. 175

High-throughput 3D Printing of Functional Biomedical Devices 

 

Cheng Sun

Professor of Mechanical Engineering

Northwestern University, Evanston IL 60208

Abstract: Advancements in healthcare have opened up the promising opportunities for personalized medicine to improve patient outcomes while decreasing costs. However, widespread adoption remains a major challenge due to the additional time and expense required to individualize treatments to patient-specific conditions. Three-dimensional (3D) printing is an emerging technology with the potential to fabricate personalized biomedical devices at low cost with extremely short lead-time. Recent achievements in the field have utilized 3D printing to manufacture arterial stents, airway tubes, bones, and dental prosthetics with relative large dimensions. However, there remains a knowledge gap for the fabrication of biomedical device with fine feature size without compromising the fabrication speed. I will talk about a highly scalable 3D printing system – continuous liquid interface production microstereolithography (μCLIP) with sub-10 um fabrication precision. I will present our recent development of fast 3D printing of completely customizable stents using the μCLIP process. Stents achieved a lateral resolution of 7.1 x 7.1 mm, with a curing thickness of 20 mm. A 20 mm length stent was printed in approximately 70 minutes and had adequate strength. The mechanical properties of 3D-printed stents with struts of 150 µm and walls thickness of 500 μm were comparable to those of a control bare metal nitinol stent. Furthermore, 3D-printed stents are customizable, could be compressed and self-expanded within a clinically relevant time frame upon deployment, and significantly improve the mechanical properties of a pig artery after deployment. Furthermore, I will discuss the method to fabricate a customized contact lens using 3D printed mold. The biocompatibility and optical performance of the lens has been further characterized experimentally using rat model.

 

Biographical Sketch: Professor Cheng Sun is an Associate Professor at Mechanical Engineering Department at Northwestern University, where he has been since 2007. He received his PhD in Industrial Engineering from Pennsylvania State University in 2002. He received his MS and BS in Physics from Nanjing University in 1993 and 1996, respectively. Prior to coming to Northwestern, he was a Chief Operating Officer and Senior Scientist at the NSF Nanoscale Science and Engineering Center for Scalable and Integrated Nanomanufacturing at UC Berkeley. Dr. Sun received a CAREER Award from the National Science Foundation in 2009 and ASME Chao and Trigger Young Manufacturing Engineer Award, 2011. Dr. Sun’s primary research interests are in the fields of advanced manufacturing necessitate developments the emerging applications in the areas of photonics, energy, and biomedical engineering. His research group is engaged in developing novel micro-/nano-scale fabrication techniques and integrated nano-system. He has published more than 70 journal papers including publications in Science, Nature Nanotechnology, Nature Materials, and Nature Communication. http://sun.mech.northwestern.edu.

For additional information, please contact Prof. Ying Li at (860) 486-7110, yingli@engr.uconn.edu or Laurie Hockla at (860) 486-2189, hockla@engr.uconn.edu