Membranes play an essential role in nature as well in many industries
including water treatment, energy, health and agro-business, where commercial
membrane technologies using synthetic polymeric and ceramic membranes have been
used for the past 50 years ago. With an annual market valued of about $10
billion and emerging markets for membrane applications in fuel cells, hydrogen
production, clean water production, wastewater treatment, air pollution control,
catalysis, food processing, drug delivery, and medical devices.
Nanoscience and nanotechnology is recognized as the key strategy to improve
conventional and develop new membrane technologies by exploring novel
nanomaterials and nano-scale processes. The development of new nanomembranes
using advanced nanofabrication approaches has rapidly progressed in recent
years, and their application beyond separation processes is extended into new
Dr Losic and his research group at Ian Wark Research
Institute (IWRI), University of South Australia, Adelaide, are working on
development of new nanomembranes with particular focus on designing their
specific functional properties toward emerging applications, including targeted
molecular separations, biosensing, and implantable drug delivery (Fig.1). The
approach is directly inspired by nature, for example biosilica membranes in
diatoms (single cell algae) where bio-mimetic principles are applied for
development of key membrane functions such as the selective molecular transport,
energy transport and signalling (sensing).
Nanomembranes for emerging applications: a) molecular separations, b) biosensing
and c) drug delivery
To design nanomembranes with desired functions and properties, Dr
Losic's group developed a series of fabrication protocols to precisely
control their most critical parameters, including pore diameters, pore geometry
and surface chemistry. The self-ordering electrochemical process is selected as
the nanofabrication approach because it is simple, inexpensive, lithography free
and highly flexible to perform structural engineering at the nanoscale.
Typical nanomembrane structures (alumina oxide) routinely fabricated in our
lab (Fig. 2) show highly organized, vertically aligned pore channels with
controllable structural dimensions, including pore diameters (10-200 nm),
inter-pore distances (50 to 400 nm), high pore aspect ratio, pore density
(109 - 1011 cm-2), porosity (10-70 %), membrane
thickness (1- 500 µm), and excellent thermal, chemical stability and
bio-compatability. The structural features of nanomembranes can be easily
controlled and tunned by adjusting conditions (electrolyte, voltage, current,
temperature and time) during fabrication.
Figure 2. SEM images
of pore structures of nanomembranes (alumina oxide) fabricated by self-ordering
electrochemical anodization. A) top surface and b)
The challenging problem of fabricating nanomembranes with shaped and ratchet
pore geometry was solved through development of a unique electrochemical
nanofabrication method called cyclic anodization. Therefore design of
nanomembranes with complex and hierarchical pore architectures allows us for the
first time to use the pore shape as a strategy for molecular separation. A new
concept for selective molecule separation using these periodic nano-ratchets is
under development to underpin new separation technology (Fig. 3).
Nanomembranes with shaped pore geometries fabricated by cyclic anodization
To advance the properties of fabricated nanomembranes we developed several
strategies for their additional structural and chemical functionalization
involving modification processes such as metal coating (chemical and
electrochemical), carbon nanotube growth, atomic layer deposition, plasma
polymerization, and surface functionalization.
Composite nanomembranes, with precisely controlled pore dimeters (down to a
few nm), were engineered with gold, nickel, carbon, polymers and nanoparticles.
The transport properties and size and chemical selectivity of membranes have
been significantly improved to meet demanding requirements for fast and
selective molecular separation.
The unique magnetic, ion-exchange, electrocatalytic and optical properties
(SERS, interferometric) of these membranes offer excellent potential, with the
development of chip based and label-free nanopore biosensors for biomedical
diagnostics and implantable drug delivery of particular interest for our group
at Ian Wark
1. D. Losic, M. A. Cole, B. Dollmann, K. Vasilev, H. J. Griesser, Surface
modifications of nanoporous alumina membranes by plasma polymerisation,
Nanotechnology, 2008, 19, 245704
2. D. Losic, S. Simovic, Self-ordered
nanopore and nanotube platforms for drug delivery applications, Expert Opinion
in Drug Delivery, 2009, DOI: 10.1517/17425240903300857
3. L. Velleman, G.
Triani, P. J. Evans, J. G. Shapter, D. Losic, Structural and chemical
modification of porous anodic alumina membranes, 2009, Microporous and
Mesoporous Materials, 2009, 126, 87-94
4. L. Velleman, J.G. Shapter, D.
Losic, Gold nanotube membranes functionalised with fluorinated thiols for
selective molecular transport, Journal of Membrane Science, 2009,
5. D. Losic, M. Lillo, D. Losic Jnr., Porous alumina with shaped
pore geometries and complex pore architectures fabricated by cyclic anodization,
Small, 2009, 5, 1392-1397
6. D. Losic, D. Losic Jnr, Preparation of Porous
Anodic Alumina with Periodically Perforated Pores, Langmuir, 2009, 25, 5426-5431
7. K. Krishna, D. Losic, A simple approach for synthesis of TiO2 nanotubes
with through-hole morphology, Physica Status Solidi RRL, 2009, 3, No. 5,
8. K. Vasilev, Z. Poh, K. Kant, J. Chan, A, Michelmore, D. Losic,
Tailoring the surface functionalities of titania nanotube arrays, Biomaterials
9. A. M. Md Jani, E. J.
Anglin, S. J.P. McInnes, D. Losic, J. G. Shapter, N. H. Voelcker, Fabrication of
nanoporous anodic alumina membranes with layered surface chemistry, Chemical
Communications 2009, 3062-3064
10. M. Lillo, D. Losic, Ion-beam pore opening
of porous anodic alumina: the formation of single nanopore and nanopore arrays,
Materials Letters, 2009, 63, 457-460.
11. M. Lillo, D. Losic, Pore opening
detection for controlled dissolution of barrier oxide layer and fabrication of
nanoporous alumina with through-hole morphology, Journal of Membrane Science,
2009, 327, 11-17.
Copyright AZoNano.com, Dr. Dusan Losic (Ian Wark Research
Institute, University of South Australia)