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Nano-Structuring of Surfaces Using Micelles
Functional surfaces with nanostructures have a wide application as (bio-) sensors or designed
microenvironments for studying interactions controlling cellular pathways and tissue formation.
Block-copolymer micelles can be used as tool for creating functional surface nanostructures
and for structuring hard materials. Experiments to transfer the polymer nanostructure formed
by the micelles into a hard substrate such as Si were successful, opening the way to more
durable, nanostructured surfaces on the scale of full wafers. The use of responsive micelle
layers as etch resists additionally leads to very interesting results. Depending on the
switching state of the surface (closed or opened micelles), a subsequent plasma etching step
leads to either nano-pillars or the complementary nano-holes in the underlying hard substrate.
Figure 1: AFM topography images of silicon surfaces covered with a monolayer of
block-copolymer micelles. After spin coating, micelles are deposited as spherical objects
(left). After treatment with a selective solvent for the polymer block that forms the
micellar core (red), the micelles open, leading to a surface covered with holes (right).
One of the major current efforts in nanoscale science is to achieve convergence of top-down and
bottom up approaches. In a cooporative effort with the project “NADIS”, a cantilever based
nanopipette, the combination of top-down structuring with surfaces that have been nanostructured
through self-organization has been achieved.
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Figure 2: Micelles can be opened and manipulated with high positional control
by local deposition of attolitre quantities of glycerol from a cantilever-based
liquid dispensing setup. |
A requirement for the realization of the potential that block-copolymer micelles hold for
controlled nanostructuring and -fabrication is the ability to predictably obtain nanostructures
of different predetermined sizes, morphologies and spacings. Different approaches for tuning
the size and spacing of micelle derived nanostructures were successfully studied. Results
obtained on PS-P2VP micelles were especially promising. The micellar size as well as the
spacings were tuned in a continuous manner over a relative scale of approx 50 %.
When using micelles to synthesize arrays of nanoparticles, an additional possibility of tuning
is offered by changing the loading conditions of the micelles. With this approach arrays of
nanoparticles of different sizes have been obtained:
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Figure 3: Arrays of metal oxide nanoparticles synthesized within micelles. The
height of the nanoparticles changes monotonically from 7.8 nm (left) to 2.7 nm right.
The lateral dimensions of the particles are distorted by the tip shape. |
Nanodispenser for attoliter volume deposition using atomic force microscopy probes modified by focused-ion-beam milling
A. Meister, M. Liley, J. Brugger, R. Pugin, and H. Heinzelmann
Applied Physics Letters, December 20, 2004, Volume 85, Issue 25, pp. 6260-6262
Contact:
Harry Heinzelmann |
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CSEM Neuchâtel, Switzerland
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