Seminar - Xihua Wang

Tuesday, April 18, 2017 10:30 am - 10:30 am EDT (GMT -04:00)


Xihua Wang, Assistant Professor, Electrical and Computer Engineering, University of Alberta, Canada


Engineered micro/nanostructures for flexible photonics and electronics


In this talk, I will show my group’s recent efforts in the design and fabrication of engineered micro/nanostructures on plastic and nanofibril paper substrates for solar energy harvesting and sensing applications. Diffraction gratings have been applied for photon management in thin-film solar cells. Leveraging the photon management ability of polystyrene nanosphere lithography, the simplicity of the self-assembly fabrication process, and highly elastomeric properties of polydimethysiloxane (PDMS), we proposed a novel stretchable transmissive hexagonal diffraction grating. The developed grating exhibits highly efficient and broadband light diffraction independent of incident light polarization and angle of incidence while concurrently being able to achieve high diffraction efficiencies of about 80%, with potential applications in solar cells and LEDs.

Cellulose nanocrystals (CNCs), wood-derived eco-friendly materials, recently attract a great attention in flexible and stretchable electronics. In addition to the unique property of dissolving in water, CNC materials could be applied for future flexible electronics for high tensile strength, low density, low thermal expansion, and non-toxicity. We demonstrated the fabrication of strain sensors on CNC-based paper substrates using stencil lithography. We also show the quantum dot (QD) doped CNC nanofibril papers for luminescent solar concentrators.

Nanomaterial based strain and pressure sensors have been reported for wearable electronics, health monitoring devices, and e-skin products. Aside from high sensitivity of these sensors, their stability and reproducibility are seldom investigated. Furthermore, due to the complicated fabrication process and re-calibration issues raised in operation, these sensors are still staying in research labs. We reported a new class of flexible sensors – digital microelectromechanical sensors for strain and force sensing using microstructure engineering of PDMS. These digital sensors can be engineered with various sensitivities for different applications, and show no degradation after 10,000 times’ bending or pressing in operation.

Speaker's Biography

Dr. Xihua Wang is an Assistant Professor in the Department of Electrical and Computer Engineering at the University of Alberta and a registered professional engineer (P.Eng.) in Alberta. He works in the area of nanomaterials and nanofabrication for photonic, electronic, and optoelectronic applications, and has published 31 papers in prestigious journal with an h-index of 18 with over 3,000 citations. Dr. Wang received the BSc degree in Physics from Peking University (Beijing) in 2003, and the Master and PhD degrees in Physics from Boston University in 2005 and 2009, respectively. He was a Postdoctoral Fellow in Dr. Sargent’s group at the University of Toronto from 2009 to 2012. He has previously received the Photonics Graduate Fellowship at Boston University (2006) and the Ontario Postdoctoral Fellowship at the University of Toronto (2010).

Invited by Professor Dayan Ban