Our research is supported by National Science Foundation, ACS-PRF, MAST Center and the University of Colorado. Detailed descriptions of on-going projects can be found in the Research page. We focus on the dynamics of nano-structured polymers. More specifically, we are interested in:
- Structure and dynamics of polymers in bulk and under confinement
- Fabrication and characterization of nanostructured materials
- Stability and Instability of the polymer nanostructures
- Nanoimprint Lithography
- Separation membranes and porous materials
06/20/2014 - Zheng's paper has been published on Polymer!In this study, we investigated the evolving structures of PS/PMMA blend films under symmetrical confinement with a normal pressure. When no external pressure was exerted on the film, the formation of PMMA wetting layer at the blend-substrate interface was predominant. With the presence of a strong external pressure, the preferential wetting was completely prevented. This was caused by the external pressure counter-balancing the wetting pressure, which drained the PMMA from the wetting layer back into isolated domains. Therefore, the study showed that pressure could be an effective means to create “neutral wetting” situation for the PS/PMMA films on preferential wetting substrates.
04/11/2014 - Maruf's Dissertation Defense
Congratulations to Maruf on passing his PhD dissertation defense! His project focused on creating high performance fouling-resistance ultrafiltration membrane via surface pattern engineering.
11/22/2013 - Liang and Zheng have passed Comps Exam!The research work of both Liang's and Zheng's have passed the examination of their committees. They have successfully advanced to doctoral candidacy! Congrats, Liang and Zheng!
10/25/2013 - Lewis's first paper gets published on Advanced Materials!In this study, we demonstrate the direct deformation and shape memory capabilities of micron-sized polystyrene particles using nanoimprint lithography. We exploit the ability to program and recovery new particle shapes to create a range of smart "Janus particles" with contrasting properties in conductivity and topography, by use of metal-layer constrained recovery.
10/17/2013 - Maruf's new paper is now published on Journal of Membrane Science!Maruf has published his recent work on patterning thin film composite membranes in Journal of Membrane Science. This paper, entitled "Fabrication and characterization of a surface-patterned thin film composite membrane” for the first time reports the fabrication of a submicron-patterned thin film composite membrane using a two-step fabrication process: 1) nanoimprinting a polyethersulfone support, and (2) forming a thin dense film atop the imprinted support via interfacial polymerization. This study provides an important perspective regarding the promise of surface patterning as an effective alternative to chemical modification for fouling mitigation in liquid-based separation membranes.
07/28/2013 - Zheng has a new paper published on Polymer!Zheng has published his most recent experimental exploration on fabricating well-aligned carbon nanoribbons via a highly controllable and high-throughput methodology. The paper, titled "Carbon nanopatterns and nanoribbons from directly nanoimprinted polyacrylonitrile: Correlation between crystallite orientation and nanoimprint process”, reports the fabrication of lithographically defined carbon patterns and nanoribbons using a common carbon precursor, polyacrylonitrile (PAN). This work is partially supported by a named award from the Beverly Sears Graduate Student Grant.
06/03/2013 - Welcome Hunter Nelson from Broomfield High School!
The group welcomes Hunter Nelson from Broomfield High School. As his science project, Hunter will work with Liang to conduct research on applications of surface-patterned shape memory polymers.
(Left: Hunter; Right: Liang)
05/31/2013 - Maruf publishes on Journal of Membrane Science!Maruf got another paper published this year in Journal of Membrane Science. The paper, titled "Influence of sub-micron surface patterns on the deposition of model proteins during active filtration”, is a continuation of his research on surface patterning of commercial membranes using nanoimprint lithography (NIL). This specific work discovered significant reduction in protein deposition on the imprinted ultrafiltration membranes due to the hydrodynamic effects associated with the surface patterns. This phenomenon was independent of solution pH and ionic strength.
03/15/2013 - Zhen passed his PhD dissertation defense!Congratulations to Zhen for passing his PhD thesis defense! Zhen's thesis, entitled "Demixing of Polymers Under Nanoimprinting Process", was presented to a five-member thesis committee; he successfully passed the scrutiny of the committee. In Zhen's doctoral research, he studied the influence of substrate surface energy on the morphological evolution of planar polymer blend films and topographically patterned films. He demontrated that high-fidelity pattern replication can be achieved on demixed blend films using nanoimprint lithography, which can then evolve into a wide range of unique and hierachical micro or nanostructures. He has authored a total of 7 research papers published on leading polymer and nanoscience journals. He is also the recipient of the 2010-2012 Teets Family Fellowship (2 out of all graduate students in engineering college). Congratulations, Dr. Wang!
03/12/2013 - Zheng's proposal to the Beverly Sears Graduate Student Grant won a named award!Zheng's proposal of "Developing a controllable and high-throughput methodology for engineering well-aligned carbon nanofibers" has been approved by the Beverly Sears Graduate Student Grant program and ranked top 5% among all submissions across the campus. Zheng has also been selected to receive the Friends of the Graduate School Named Award, in the honor of private donors who support the research and creative goals of graduate students. Only the highest ranked proposals are considered for the small number of named awards, and recipients receive the full amount of their request.
02/18/2013 - Liang's paper has been accepted to be published on Soft Matter!In this report titled "Photocrosslinking-induced Phase Separation in Evaporative Solvents: Formation of Skin Layers and Microspheres", we investigated the structure formation of films obtained via photocrosslinking of precursors during the evaporation of solvents. The film structure after processing is highly hierarchical, featuring a skin layer on top of a layer of microspheres formed via reaction induced phase separation mechanism. More importantly, the feature size of structures can be readily achieved by changing processing parameters including N2 flow rate, UV intensity and precursor concentrations.
02/08/2013 - Zheng's paper has been published on LangmuirWe studied the "influence of substrate confinement on the phase-correlation in the capillary breakup of arrays of patterned polymer stripes". For the two extreme cases of viscosity ratios we investigated, in-phase breakup of strongly confined immiscible polymer stripes was always observed, regardless of the specific geometry.This was because the rigid substrate suppressed undulations on the polymer stripes from being developed perpendicularly to the substrate and, therefore, lateral undulations between neighboring stripes became strongly coupled.
01/09/2013 - Maruf's paper is now published on Journal of Membrane Science!
In this study titled "Use of nanoimprinted surface patterns to mitigate colloidal deposition on ultrafiltration membranes", we demonstrate that submicron patterns can be successfully imprinted onto a commercial polysulfone ultrafiltration membrane surface using nanoimprint lithography (NIL) without sacrificing much of its permeability properties. The presence of these patterns led to significantly improved deposition resistance during filtration of colloidal silica particle suspensions. These results suggest a promising chemical-free manufacturing route to achieve antifouling properties for commercial ultrafiltration membrane.