Nano Torsion Probes for the Atomic Force Microscope (AFM)
By Dr. Arthur Beyder, Marianne Timm
Figure
1 illustrates the principle of AFM operation: an ultra-sharp tip (radius of
curvature ~50nm) is rastered over the surface of a sample and force exerted by
the sample on the tip is transduced through bending of a microscale cantilever. Cantilever movement is typically monitored by
a focused laser beam reflected off the cantilever (optical lever) onto a
position sensitive photodetector (PSPD). Similar in function to a record player, the AFM
reads the topography of the sample showing a different image from a traditional
"microscope" and is capable of visualizing nanometer features. The direct nature of this instrument's
interaction with the sample allows nanoscale manipulations, such as molecular nanosurgery.
The
atomic force microscope was developed for measuring hard, dry surfaces, such as
semiconductors, and achieves its best resolution in vacuum at the lowest
possible temperature and minimal thermal noise.
Yet, the ability of the AFM to measure forces in single molecules and
cells makes the AFM attractive to biologists. However, biological samples, such as living cells are extremely soft and
work best at body temperature in saline solution, limiting AFM resolution. First, cells are roughly 1000 times softer
than the softest available cantilevers, limiting cantilever bending. Second, the saline solution increases viscous
drag on the cantilever reducing its frequency response compared to its operation
in air or vacuum. This results in a
cantilever that is slow and heavy-footed. Third, commercially available cantilevers are often biomorphs that may
warp in liquids and high temperatures.
AFM sensitivity is
limited by cantilever sensitivity, i.e., how much the angle changes with a given
force. The established method for
increasing cantilever compliance (sensitivity) is to increase cantilever length
while keeping its thickness constant. However, a long cantilever in saline solution has more surface area and
hence more viscous drag and a lower frequency response. Accordingly, this method is suboptimal for
increasing AFM sensitivity in the measurement of biological samples.
Doctors
Arthur Beyder and Frederick Sachs working at the Center for Single Molecule
Studies at the University of Buffalo solved these problems by creating the
patented, Nano Torsion Probe, which is illustrated in figure 2. This probe minimizes the problems of the
atomic force microscope for biological samples by utilizing <100nm torsion
hinges (SiN) and decreasing the moving block area (Si). The small size of the mirrored
block (~ 20x20 μm) minimizes the viscous drag. The torsion hinges allow the probe to only move in one axis (rotation), making
the interpretation of the data simpler than a cantilever, which can twist and
bend. Thin hinges allow for a decrease
in spring constant and a decrease in moving area resulting in high resonant
frequency, and a lower viscous drag as well as an increase in optical lever gain. These benefits help to further improve the
signal to noise ratio. Additionally, the
symmetrical design of the Nano Torsion Probes greatly reduces temperature and
solution induced warping. Accordingly,
AFMs with the Nano torsion probe are optimal for investigation of soft samples
in viscous environments and provide higher compliance and frequency response. Not only are these probes optimal for soft
samples in viscous environment, but they are 10-fold softer, 10-fold faster,
and 100-fold more sensitive than traditional cantilevers. Furthermore, the Nano Torsion Probe can be used
in place of traditional cantilevers with little or no change in cost.
Nano Torsion
Probes allow scientists to get more data from the same experiment with no additional
effort or cost. This increased
sensitivity allows for the exploration of new frontiers in biology. Trial samples of single axis Nano Torsion
Probes are available. For more
information regarding this patented technology, contact Dr. Arthur Beyder or Dr. Frederick Sachs.
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Recap of MN
Nano's 2009 Legislative Session efforts
By Lynne Osterman, Shweta Sharma
MN Nano has supported and advocated at
the Minnesota Legislature for the creation of the North Star Rising (NSR), the progress
and outcome of which resulted in the formation of what is called the State
Science and Technology Strategy Committee. What follows is a recap of MN
Nano's 2009 Legislative Session efforts and where things are now in terms of the
"S&T Strategy Committee."
State Science & Technology Strategy
Committee
What do you do if people come to you year after year
with somewhat related ideas, approaches, suggestions, solutions, mechanisms,
opinions, concepts, rationales, objectives and the
like? Sometimes, paralysis occurs. Actually, it's human nature. When faced
with a myriad of ideas to the point where it feels like, "Well, we've got to do
something, so let's do
this...," you toss a dart toward the awaiting
board, a dart that in its wisdom is about to select out of the seemingly
hundreds of ideas, a dart that lands on: Number 69 on the Priority
List. But in the absence of a priority list, we go with the random choice our dart has selected for
us.
In the case of tech-based economic development,
however, a state can't be competitive by throwing darts at a board to see what
sticks. In the case of tech-based economic development, Minnesota
cannot be competitive without a priority list. The problem is,
Minnesota cannot even agree as to how the priority list should be made in the
first place. Rather, we've grown accustomed to the annual pilgrimage to the
Minnesota Legislature and Governor Pawlenty for the past eight years, asking them to
throw the darts to whittle down the options and then with sometimes arguably
little regard to long-term viability or lasting impact (think "bio-zones"),
something might get passed.
The Priority List
The absence of a priority list - so ideas can be
evaluated and ranked as they are pulled out of the Suggestion Box - has plagued our
state long enough. At least that is what a collection of people from the science
& technology community believe. In 2008, two reports* were
commissioned which, upon release, had a number of findings in common. A major
conclusion from both indicated that Minnesota's lack of a
tech-based economic development strategy had become a
liability to the state's competitive ability. When compared to where other
states (& countries) are likely to be even a mere 10 years from now, by
leveraging their respective long-term plans, the studies predict, Minnesota is
going to be lagging far behind.
The science and technology community proposed the creation of the NSR, a
statewide commission-of sorts, that would have the responsibility for creating a
visionary, comprehensive, attainable and measurable tech-based economic
development strategy for the North Star State. NSR objectives would include: - Establish the tech-based economic development strategy
against which the aforementioned annual myriad of Suggestion-Box approaches
would be evaluated.
- Benchmarking and evaluation responsibilities to be sure goals & objectives
were actually achieved, results measured and shared.
- Assist the
legislature, the governor, the state employees working with economic development
programs, municipalities and regions in determining, implementing and evaluating
priority programs and activities in light of the over-arching tech-based
economic development strategy.
Crawl before you walk
Like all good tales of the twists and turns seemingly
brilliant legislative proposals have in their wake, the NSR proposal had a
couple things going against it by the time the 2009 Legislature convened in
January. First, the NSR proposal was not in full bill form for
legislative introduction and committee discussion at the outset of the 2009
Session. Second, due to the first, there was no public discussion
about the absence of a Priority List, so the Annual Pilgrimage to St. Paul with
a myriad of ideas out of the Suggestion Box was in Full Swing by the time the
NSR concept was on the table (with some of the ideas building up steam and
burning political capital, an irrefutable repercussion).
The net outcome of the original NSR legislation was the
creation of a public-private project, with the underlying hope the said
group would
eventually recommend a structure to be given the responsibility and
accountability for all of the deliverables previously noted for the NSR
entity. The legislation passed in May 2009 stated the Commissioner of the Department of Employment shall lead a
public-private project to advise state agency collaboration to design,
coordinate, and administer a strategic science and technology program for the
state designed to promote the welfare of the people of the state, maximize the
economic growth of the state, and create and retain jobs in the state's
industrial base and [report back to the Legislature] by January 15, 2010 on
the activities of the project and must recommend changes or additions to its
organization, including specific recommendations for necessary
legislation.**
Coined by DEED Commissioner Dan McElroy the "Science
and Technology Strategy Committee"(STSC), the group first
convened on October 6 and has two other meetings scheduled before the end of the
year. Since the group has met only once, it might seem
premature to predict an outcome.
Prediction: The outcome of the STSC will be:
No comment on the design of a
strategic S&T program for the state that would create a roadmap for
Minnesota tech-based economic development.
Another litany of individual suggestions to
the legislature for the 2010 Session.
Possibly a list of suggestions to the
legislature for the 2011 Session.
As opposed to accomplishing:
Research and documentation of how other
states' (& countries') long-term strategies are already producing
significant tech-based economic development outcomes An outlined roadmap for the creation of a
significant entity representative of the S&T community, policy makers and
the academic sector to develop a tech-based economic development strategy for
Minnesota (so no one single force can be "blamed" for not getting things
done, and finally, everyone who has a stake in the outcome will have a role in
establishing & delivering outcomes) A game plan to get the entity established
early in the 2010 Session, charged with measurable deliverables, so it can be up
and running no later than May, 2010 Minnesota starts creating an Eco System to
support tech-based economic development, linking current assetts with a quality
backdrop for evaluating future ideas so we can make Priority Lists and start
checking things off The List
The fun thing about predictions is they can be
hilariously, or fortuitously, incorrect. For the sake of Minnesota's science &
technology future ability to compete, let's hope this prediction is 100%
WRONG.
(Note: technically, neither report will
characterize the 10-year timeframe outcomes using the same verbage as noted
above) ** HF2088, Sect. 16 (42.29-43.22)
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An Amazing History but the Hard Disk Drive Industry is Just
Getting Warmed Up
By Ed Gage, Eric Hockert
The magnetic hard disc drive (HDD)
industry has been amazing in its ability to increase drive capacity and
performance during its history. For
example, bit storage density has gone from the 5 kilobits per square inch of
the original IBM Ramac drive to currently
approaching 500 Gbits per square inch in upcoming products. This increase of 10 million times has been
accomplished by 50 years of continuously scaling down the critical dimensions
of the recording system and incorporating new technologies. Nanotechnology has played a key role. Examples include: the media recording layer designed to self order in a granular structure with grain sizes on the order
of 10 nm in diameter, the critical dimensions of the magnetic writer which are on the
order of 10 nm, and the recording head maintained at a distance of a couple
of nanometers above the spinning disk by using a high pressure air bearing and
a thermo-mechanical actuator.
As HDD technology approaches areal
densities of 1Tbit per square inch, we need to further reduce the grain area
in the media in order to maintain enough grains per bit which is critical for a
good signal to noise ratio. As we reduce
the grain size, its magnetic energy is reduced and the magnetic orientation
which stores the information becomes susceptible to thermal fluctuations. One solution is to increase the magnetic energy
density of the media material. This
leads to difficulties in producing a magnetic field from the recording head
that has sufficient strength to produce a high quality magnetic pattern in the
media. It is estimated that this
superparamagnetic effect will limit areal densities of today's recording system
to about 1Tbit per square inch.
One solution to superparamagnetic
effects is to use high anisotropy materials such as FePt and heat them up
during the recording process to lower their coercivity to the point it can be
written with available head fields. This
approach is called Heat Assisted Magnetic Recording, HAMR [1]. As we heat the media to near the Curie
temperature, we want to avoid heating neighboring tracks to prevent increased
thermal fluctuations and erasure. The
track pitch at 1 Tbit per square inch is about 60 nm. How can we produce a small well confined hot
spot on the track to be recorded? Optical data storage uses a highly focused laser to create thermal spots
on the order of 200 nm or larger. This spot
size is too large to limit the heat to the desired track pitch.
Figure 1. A top down view of the gold lollipop near
field transducer is shown in a) and an air bearing surface (ABS)
view (b) of the integrated HAMR head shows the magnetic pole, peg of the near
field transducer, and the optical waveguide core. At Seagate, we have developed a
plasmonic antenna device and integrated it into our recording heads [2]. These plasmonic devices are excited by a
tightly focused laser beam from a planar solid immersion mirror integrated into
a magnetic recording head. The
"lollipop" near field transducer (NFT) is shown in figure 1. It consists of a gold disk whose dimensions
are chosen to yield a plasmonic resonance at 830 nm. The peg serves to couple to and confine the
field in the recording media. When
integrated with the high anisotropy media with the correct thermal properties,
we have shown that it is possible to confine the heat and record magnetic
tracks on the order of 50 nm wide as shown in figure 2.
The hard disk drive industry has an
impressive history of incorporating new technologies such as giant
magneto-resistive sensors and nanometer resolution thermal actuators to
continue to increase capacity and performance of data storage. Heat Assisted Magnetic Recording is being
developed to allow another order of magnitude increase in areal density.

Figure 2. a) A magnetic force microscope image shows a
recorded HAMR track on a high anisotropy FePt disk. In b) the signal amplitude is plotted versus
cross track position from a scan of the reader across the recorded track
showing the ~ 50 nm recorded track width.
References:
[1] M. H. Kryder et. Al, Proceedings of the IEEE, 96,
1810-1835 (2008)
[2] W. Challener et. al. Nature Photonics 3, 220 - 224
(2009)
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Handling Ownership Issues For A Mutually Satisfying Collaboration
By Benjamin Tramm
Nanotechnology, by its very nature, typically requires
expensive and highly specialized machinery. For this reason, many early stage companies must look to collaboration
with others in order to get off the ground. Such collaboration can provide access to lab space, for example, and may
also provide access to other resources, such as the specialized knowledge of
others from diverse technological backgrounds.
Collaboration does not come without its risks, and savvy
companies will consider these risks carefully before engaging in a
collaborative effort. One of the
considerations that must be carefully thought out is how to handle any
intellectual property that may be developed through the collaboration.
Absent an agreement to the contrary, the default ownership
model in the United States is that an inventor or author owns the complete
rights to intellectual property associated with his or her creation. When multiple people collaboratively invent
or author, each is granted an equal and undivided interest in the
creation. This model can lead to
problems down the road. Say, for
example, that one inventor at company A begins to commercialize a patented
technology. The other inventor at
company B could then turn around and sell his or her interest in the invention
to company A's biggest competitor, giving the competitor an equal and undivided
interest in the patented technology.
The parties can, however, contract out of this default model
to define their own model for intellectual property ownership. In order to develop a mutually beneficial
arrangement, it is usually necessary for the parties to engage in an open
discussion about each party's interests.
Assignments or licenses can be used to define an ownership model that is
mutually satisfying. The result should
be a written collaboration (or "co-development") agreement that specifies the
agreement of the parties in clear and unambiguous terms.
If patents or trade secrets are desired for any of the
technology being developed, it is important to have a written non-disclosure
agreement in place. As its name implies,
a trade secret will be required to be kept in secret. If patents are to be applied for, it is
important to be sure that the technology remains confidential until the
necessary patent applications are filed. Most countries outside of the United States require absolute novelty,
which typically means that a public disclosure of the invention could result in
a loss of some or all of the intellectual property rights. A non-disclosure agreement is useful to ensure
that the sharing of information between companies is not considered a public
disclosure.
A well developed collaboration agreement can be a catalyst
to collaboration, by defining the framework for the collaboration. Knowing that the intellectual property issues
have been resolved up front, the parties can be free to engage in a mutual
exchange of ideas.
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Enewsletter Work Group
Shweta Sharma (MN Nano ENewsletter Chair)
Sr. MEMS Engineer
Goodrich Corporation
 Eric Hockert
Technology Marketing Manager
University of Minnesota
Technical Advisor
Merchant & Gould
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Upcoming Events
Seminars at the Center for Nanostructure Applications
Check out the CNA calendar for upcoming seminar topics and dates. University of Minnesota |
MN Nano Membership Briefing
December 2, 2009 St. Paul College Join MN Nano members and the State Science & Technology Committee to discuss statewide collaboration opportunities, the legislative agenda for this session, for an
update on the potential Nano Commercialization Center and a tour of the new clean room the College debuted
this past year. Registration and continental breakfast at 7:30 a.m., program at
8, concluding with tour at 10. This event is $10 for MN Nano members
and $20 for non-members. Parking is FREE for all attendees. To register,
call 763.245.3902 or email Lynne Osterman
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MN Nano Nano/MEMS Sensors Special Interest Group
The objective of the Nano/MEMS sensor special interest work group (SIG) is to build
a forum to foster collaborative research and to enhance the prospects of
improved private sector and university research. If you have suggestions for speaker topics, speakers for the upcoming SIG event (early 2010) or want to get more involved in the Sensors SIG, please contact Dadi Setiadi
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Interested in reaching the engineers, researchers and
technicians you need to keep your company moving forward? MN Nano is starting a
Student Chapter and is looking for a Host Company to sponsor student membership
fees. The sponsoring company will receive promotional credit
on MN Nano's web site. For more information on how your company can become a 2010 Student Chapter Sponsor, please contact Lynne Osterman
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Want to learn more about MN NANO? Visit our website
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