Newsletter, January 2014

    MIT Materials News that Matters

    January 2014
    Materials Processing Center at MIT MIT Dome
    77 Massachusetts Avenue
    Cambridge, Massachusetts 02139
    Faculty Highlight: A. John Hart 
    Making things big
    Mechanical engineering professor A. John Hart explores the science and technology of nano manufacturing.

    Associate Professor of Mechanical Engineering A. John Hart hopes progress in the science and technology of micro and nano manufacturing will enable new technologies ranging from consumer electronics and medical devices to arts and crafts.

    Associate Professor of Mechanical Engineering A. John Hart
    with a folding paper cylinder. Paper's ability to fold and unfold many times and retain its integrity is a motivation for Hart's
    work on origami-inspired engineering.
    Photo: Denis Paiste, Materials Processing Center

    "Being in mechanical engineering, in the area of manufacturing, I feel especially motivated to do things that can make a practical impact in how materials are made and how everyday things are improved," Hart says.

    His expansive interests include carbon nanotubes and graphene, 3D printing and other additive manufacturing processes and origami-inspired engineering. He is also interested in images of nano and micro-scale structures as media of art and communication, most famously his "Nanobama" microscopic faces of Barack Obama (2008) that were noticed by newspapers from Japan to Czechoslovakia and drew attention from the White House. The tiny carbon nanotube images of President Obama were made from patterned carbon nanotubes and imaged using a scanning electron microscope.  Read more. 

    Improving Carbon Nanotube Consistency in the Lab   
    Mechanical engineering professor, graduate student automate chemical vapor deposition process with bench-top 'Robofurnace.'
    Video: Robofurnace operation speeded up. Courtesy Ryan Oliver, Mechanosynthesis Group
    Video: Robofurnace operation speeded up. Courtesy Ryan Oliver, Mechanosynthesis Group

    Bench-top automation in the lab can result in reduced variation in carbon nanotube growth, as well as better production of other nanomaterials, according to a research report by a team who originated the work at the University of Michigan, and now reside at MIT.

    Visiting graduate student Ryan Oliver and Associate Professor of Mechanical Engineering  A. John Hart published their results in "Robofurnace: A semi-automated laboratory chemical vapor deposition system for high-throughput nanomaterial synthesis and process discovery" in the Review of Scientific Instruments in November 2013.

    Oliver says the reductions in variation can accelerate the research cycle. Robofurnace demonstrated that controlling the experiment has benefits. A parametric study using Robofurnace boosted density of CNT forests grown in the Hart lab by at least 10 times over previously reported values in the same laboratory. Read more.

    Carbon Nanotubes Under Stress

      MIT Post-Doc Mostafa Bedewy shows complex competition between chemical activation and mechanical forces in growing CNT forests.

    VIDEO: Taking the Measure of Nanotube Growth
     VIDEO: Taking the Measure of Nanotube Growth

    Better production methods for carbon nanotubes will require control of both chemical and mechanical factors in their growth, a recent report by MIT researchers show.

    Postdoctoral Associate Mostafa Bedewy, working with Associate Professor of Mechanical Engineering A. John Hart, demonstrated that competition between the chemical activation of carbon nanotubes growing on seed particles and the mechanical coupling among growing carbon nanotubes of different sizes, leads to the waviness of individual strands seen in highly magnified views of CNT forests.

    Building on earlier work showing that larger diameter carbon nanotubes grow at a faster rate than smaller diameter CNTs, but stop growing sooner, the new work found that larger diameter CNTs were subject to greater mechanical stress. Maximizing the number of same-sized seed nanoparticles for nanotube growth and reducing variation in the space between them could produce straighter, denser, more evenly sized nanotube forests, the research suggests. Read more.

    Shining a Light on Tiny Polymer Shapes

    Visiting graduate student studies high-throughput manufacturing of precisely shaped micro particles.

    Visiting graduate student Ryan Oliver with a microscope. Oliver's projects under Associate Professor of Mechanical Engineering A. John Hart include the Robofurnace, an automated system for making carbon nanotube forests and studying their growth, and high-throughput manufacturing of polymer microstructures for biosensing. Photo: Denis Paiste, Materials Processing Center

    Ryan Oliver, a visiting graduate student is working on a technique called Maskless Fluidic Lithography that allows creation of unique shapes in a liquid polymer such as PEG-DA by exposing it to patterned ultraviolet light, a process known as photo-polymerization. 

    For example, working with a common biocompatible polymer, polyethylene glycol diacrylate (PEG-DA), Oliver uses a projector as a mask to pattern shapes. Unlike the wafer masks used in semiconductor processing, which are produced as single use items, the integrated projection system allows for rapid change of the pattern.

    Key to the system is a Texas Instruments Digital Micromirror Device (DMD), which can be reconfigured easily by turning on and off micro mirrors to produce a multitude of shapes. "Because the mirrors are so fast, we can make decisions very quickly, which is hard to do with a masked system. You would spend several days ordering or fabricatinga mask rather than milliseconds if you needed a new pattern," he says.  

    The vision is to use particles that are designed to work together and act as a sensitive biosensor. To realize the vision, Ryan has a goal to produce micro particles from about 250nm to about 100 microns with a library of shapes such as diamonds, triangles, squares and octagons. Read more.

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