Ji-Huan He talks with
ScienceWatch.com and answers a few questions about
this month's Fast Breaking Paper in the field of
Engineering. The author has also sent along images of
Article Title: Electrospun nanoporous spheres with
Authors: Xu, L;He,
Journal: INT J NONLINEAR SCI NUMER SIM
* Donghua Univ, Modern Textile Inst, Shanghai 200051,
Peoples R China.
(addresses have been truncated)
Why do you think your paper is highly
This paper suggested a new approach, in which a traditional Chinese drug
called Yunnan Baiyo is used as an additive, in order to produce nanoporous
microspheres by electrospinning, which has always been recognized as an
efficient technique for the fabrication of continuous nanofibers. We
utilized this technology to produce nanoporous materials, which offer the
potential for direct fabrication of biologically based, high-surface-area
porous materials without the use of multiple synthetic steps, or
postprocessing surface treatments.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Nanoporosity can be controlled by tunable voltage applied in the
electrospinning process using the concept of "electrospinning-dilation"
(For a detailed explanation, see: Lan Xu, et al., "Electrospun
Nanoporous Microspheres for Nanotechnology," International Journal of
Electrospun Nanofibers & Applications 1:105-21, 2007)
Would you summarize the significance of your paper in
The electrospinning process involves the application of a very high voltage
between the spinnerette and the collected plate. A higher applied voltage
leads to an elongated cone to overcome the surface tension of the
electrospun solution or melt. When it exceeds a threshold voltage, a jet is
emanated. During the electrospinning process, the charged jet is
accelerated by a constant external electric field, and the spinning
velocity probably exceeds the velocity of sound in air for a very short
Imagine that the applied voltage was infinitely high, while the distance
between the spinnerette and the collected plate was infinitely long, and
the velocity would be infinitely large; according to the mass conservation
equation, (see He JH, et al., "Mathematical models for continuous
electrospun nanofibers and electrospun nanoporous microspheres,"
Polymer International 56 : 1323-29, 2007), the radius of the
jet decreases with the increase of the velocity, thus the diameter of the
charged jet might become zero! This is, of course, impossible.
Macromolecules of the polymers are compacted together tighter and tighter
during the electrospinning process. There must be a critical minimal radius
for continuous ultrafine fibers. In cases when the radius of the jet
reaches the value of the critical value and the jet speed exceeds its
critical value, in order to keep the conservation of mass equation, the jet
dilates by decreasing its density, leading to porosity of the electrospun
fibers; we call this phenomenon an electrospinning dilation.
Where do you see your research leading in the
Electrospun nanofiber technology actually bridges the gap between
deterministic laws (Newtonian mechanics) and probabilistic laws (quantum
mechanics). One of the most challenging applications of electrospun
nanoporous materials is for invisibility devices (e.g., stealth plane,
Do you foresee any social or political implications for
Because of their ultra-high specific surface, nanoporous structures, which
are potentially of great technological interest in the development of
electronic, catalytic, and hydrogen-storage systems, invisibility devices,
and etc., have received much attention recently.
Pore structure and connectivity determine how microstructured materials
perform in applications such as adsorption, separation, filtering,
catalysis, fluid storage, and transport, as electrode materials or as
reactors. Far-reaching implications are emerging for applications including
medical implants and cell supports, materials which can serve as
instructive three-dimensional environments for tissue regeneration and
other potential uses.
Professor Ji-Huan He
Modern Textile Institute
Shanghai, People's Republic of China
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