Cluster I: Tools for Integrated NanoBiology. As
biology begins to ask more quantitative and analytical questions about the nature
of the cell, it needs new tools to study subcellular structures that have nanoscale
dimensions. An important task is to build bridges between the physical and biological
sciences. The physical sciences offer to biology new measurement tools and new procedures
for analyzing the information obtained. In turn, biology offers to the physical sciences
an enormous range of engaging problems, and stimulating examples of very sophisticated,
functional biological systems. It also offers the opportunity to think about hybrid
systems that combine biological and non-biological components.
|Figure 3. A CMOS / Microfluidic chip consisting of a CMOS integrated circuit with a microfluidic system on top. By energizing microcoils, the chip can trap and move magnetic beads and attached cells through the fluid above for cell sorting or the assembly of artificial tissues.
The interface between the biological and physical sciences is one with enormous promise
for fundamentally new science, and, ultimately, technology. By supporting collaborations
between investigators in DEAS, Chemistry, the Medical School, and the School of Public
Health at Harvard, Cluster I will catalyze and expand a series of very effective collaborations
across the physical-biological interface.
We expect three outcomes: Tools for Cellular Biology
and Tissue Culture. One of the major contributions that the physical sciences
can offer to biology is new physical tools to provide new kinds of information
about cells and tissues. The Science and Engineering of Interfaces between Animate
and Inanimate Systems. In research, this will contribute to the studies of cells
in cell culture, and to the assembly of groups of cells of the same or different types.
In society, it will contribute to engineering the interface between patients and prostheses. Tools
for Development of Drugs. The control over cells afforded by these studies is
the basis for entirely new types of bioassay that will be important as the pharmaceutical
industry moves away from information-poor animal assays in preclinical studies toward
more informative studies based on primary human cells.
Cluster II: Nanoscale Building Blocks. Tremendous
progress has been made in the synthesis of nanoscale structuresnanoparticles, nanowires
and nanotubesthat serve as building blocks for new devices and applications. However
many challenges remain. These include the synthesis of nanostructures with well-defined
sizes and shapes, the synthesis of new classes of materials, the in-depth characterization
of newly developed nanostructures, the rational organization of these nanostructures
into complex functional structures, and the fusion of nanoscale building blocks with
state-of-the-art processing techniques, including e-beam lithography and focused-ion-beam
sculpting to build novel devices.
|Figure 4. Nanoscale building blocks.
(a) 2-D array of CdSe nanocrystals.
(b) CdSe nanorods.
(c) Crystalline La1-xBaxMnO3 nanocubes.
(d) Nanometer-sized Pd spherical cups.
(e) Single-crystalline VO2 nanobeams.
(f) Single-crystalline nanobelts of NbSe2.
A broad multidisciplinary, multi-investigator research program is proposed that is
designed to address these challenges. The proposed research is solidly built upon
the participants expertise on the synthesis and characterization (both experimental
and theoretical) of nanostructured materials. At the core of the program is the rational
synthesis of new classes of nanostructures that exhibit new size-dependent properties
that are distinct from bulk materials, with an emphasis on semiconductor and metallic
nanostructures with unconventional shape, as well as on zero-, one- and two-dimensional
nanostructures based on metal chalcogenides that have not been made previously. The
incorporation of nanostructures into novel device geometries will constitute another
important part. These devices will be used to characterize the physical and chemical
properties of nanoscale materials and to test their technological applicability. Understanding
the behavior of these nanoscale building blocks through theoretical investigations
will be an important part of the proposed efforts, because it is essential for furthering
the scientific and technological frontiers of nanomaterials.
|Figure 5. Physics Today (Dec. 2003) that contains the review Imaging Electron Flow by Topinka, Heller, and Westervelt.
Cluster III: Imaging Electrons at the Nanoscale. Electrons
inside nanoscale structures display striking quantum behavior that arises from the
confinement of electron waves. By visualizing how electron charges and spins move
through nanoscale systems, we can understand the fundamental science and develop new
quantum devices. These range from a transistor that control an electron charge for
single-electronics, or spin for spintronics, to a quantum switch for new approaches
to electronics, to fully quantum mechanical dot circuits that control qubits for quantum
The goal of Cluster III is to develop new ways to image
the quantum motion of electrons inside nanoscale systems. This is difficult, because
the electrons are buried inside the structure, and because low temperatures are necessary.
Custom-made microscopes and new imaging techniques are needed. This Cluster brings
participants who are known for their skill in designing custom-made scanning probe microscopes (SPMs) and in developing new ways to image the quantum behavior of electrons
inside nanoscale systems. A close collaboration with the MBE Lab at UC Santa Barbara
to make custom-designed heterostructures makes this work possible.
Expected outcomes of this research are: Scanning probe microscopes for imaging electrons
inside devices New microscopes and imaging techniques will be developed to see electrons
inside nanoscale semiconductor structures, that will be used in the future to characterize
and understand new devices. Scientific understanding of electrons inside nanoscale
structures. To make new nanoscale devices, we need to understand the motion of electron
charges and spins, and the effects of interactions between particles. Research in
this cluster will develop this scientific knowledge. Developing new types of heterostructure
devices Advances in MBE growth can be used to sophisticated structures including self-assembled
InAs quantum dots. Imaging electrons in these structures will enable the development
of new devices based on electron charge and spin.