from:
www.nanoscience.gatech.edu/zlwang/paper/2007/07_MRSB_2.pdfNW=Nanowire
NT=Nanotube
Nano-BiotechnologyIntegration of nanosystems and biosystems
is a multidisciplinary field that has
the potential for tremendous impact on biology,
chemistry, physics, biotechnology, and
medicine. The combination of these diverse
areas of research promises to yield revolutionary
advances in healthcare, medicine,
and the life sciences through, for example,
the creation of new and powerful tools that
enable direct, sensitive, and rapid analysis
of biological and chemical species. Patolsky
et al.52 have demonstrated the first application
of NW nanosensors for ultrasensitive
detection of proteins down to individual
virus particles as well as multiplexed recording
of these species using distinct NW elements
within a sensor device. In addition,
Patolsky et al.60 have demonstrated an unprecedented
approach for investigating the
electrical properties of hybrid structures
consisting of arrays of NWFETs integrated
with the individual axons and dendrites
of live mammalian neurons, where each
nanoscale junction can be used for spatially
resolved, highly sensitive detection, stimulation,
and/or inhibition of neuronal signal
propagation. Details are described by
Patolsky et al. in this issue. Arrays of
nanowire–neuron junctions enable simultaneous
measurement of the rate, amplitude,
and shape of signals propagating
along individual axons and dendrites. The
configuration of nanowire–axon junctions
in arrays, as both inputs and outputs,
makes possible controlled studies of partial
to complete inhibition of signal propagation
by both local electrical and
chemical stimuli. This revolutionary development
opens a new field in integrated
nano-biotechnology.
Nanoelectromechanical Systems
The development of novel technologies
for wireless nanodevices and nanosystems
is critically important for in situ, real-time,
and implantable biosensing and biomedical
monitoring. Nanosensors are currently
under intense development for ultrasensitive
and real-time detection of biomolecules.
An implanted wireless biosensor, for
example, requires a power source, which
may be provided directly or indirectly. It is
highly desirable for wireless devices (and
required for implanted biomedical devices)
to be
self-powered without the need
for finite-lifetime batteries. Using aligned
ZnO NWs grown either on a crystal substrate
or a polymer substrate,61 an innovative
approach has been demonstrated for
converting nanoscale mechanical energy
into electric energy.20 By deflecting the
aligned NWs using a conductive atomic
force microscope (AFM) tip in contact
mode, the energy that was first created by
the deflection force and later converted
into electricity by the piezoelectric effect
has been measured to demonstrate a
nanoscale power generator. The operation
mechanism of the electric generator relies
on the unique coupling of piezoelectric
and semiconducting dual properties of
ZnO as well as the elegant rectifying function
of the Schottky barrier formed between
the metal tip and the NW.62
This research demonstrates the feasibility
of harvesting energy from the environment,
such as converting mechanical
energy (e.g., body motion or muscle
stretching), vibrational energy (e.g.,
acoustic or ultrasonic waves), and hydraulic
energy (e.g., body fluid and blood
flow) into electric energy for self-powered
nanosensors and nanosystems. It also has
a huge impact on miniaturizing the size of
integrated nanosystems by reducing the
size of the power source and improving its
efficiency and power density. Piezoelectric
FETs and diodes as well as force sensors
have also been demonstrated using NWs.