Dr. Leon M Bellan

Previous research: Leon Bellan's thesis work focused on studying both electrospinning and electrospun nanofibers. He performed the first direct measurement of fluid velocity in an electrospinning jet using fluorescent tracer particles. Due to the strong elongational flow in an electrospinning jet, the fibers produced by such a jet are thought to have significant molecular orientation. Using an atomic force microscope, he measured the Young’s moduli of individual nanofibers and showed that the resulting values were larger than typical bulk values, indicative of molecular orientation.  To support this conclusion, he used polarized Raman spectroscopy to quantitatively measure the molecular orientation of an individual nanofiber, and compared these results to values for film and fibers produced using other techniques. Using the elongational flow in the jet, he stretched and embedded isolated fluorescently tagged ? DNA molecules in polymeric fibers to be used for genomic analysis. Electrospinning tends to produce random mats of fibers; consequently, there is much work devoted to techniques for depositing fibers with controlled orientation and/or position. Bellan developed a system that uses time-varying electric fields to steer and confine the charged electrospinning jet, allowing one to draw single-fiber patterns. As a potential source for this system, he modified a commercial robotic system designed for introducing samples into mass spectroscopy systems using electrospray ionization from chip-based nozzles (Advion NanoMate). The modified system is able to deposit electrospun fibers from 5µm nozzles (as opposed to the syringe needles typically used in the field) and produces more uniform deposition compared to other electrospinning systems. After graduating, Bellan worked as a postdoc developing polymer-coated nanoscale resonators (NEMS) to detect trace amounts of nitrotoluene compounds in vapor at atmospheric pressure.

Current research: While working on his thesis research in the Craighead group at Cornell University, Dr. Bellan developed a technique for fabricating nanochannels in polymer matrices using sacrificial nanofibers. He demonstrated that these channels were accessible by flowing dye or fluorescently tagged DNA molecules through them. Inspired by a presentation by a doctor from the Weill Medical College of Cornell, Dr. Bellan started modifying this technique to produce 3D networks of capillary-sized channels (approx. tens of microns in diameter) in polymer matrices to be used for engineered tissue constructs. This novel technique relies upon sacrificial melt-spun sugar (commonly known as cotton candy) to form the 3D microchannel network. Bellan has demonstrated that these channel networks allow blood flow and that the channels are of the same average size and spacing as typical capillaries.