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www.sciencedaily.com/release...3303.htm
ScienceDaily (June 16, 2009) — Researchers at New York University have
created a method to precisely bind nano- and micrometer-sized
particles together into larger-scale structures with useful materials
properties. Their work, which appears in the latest issue of the
journal Nature Materials, overcomes the problem of uncontrollable
sticking, which had been a barrier to the successful creation of
stable microscopic and macroscopic structures with a sophisticated
architecture.
The long-term goal of the NYU researchers is to create non-biological
materials that have the ability to self-replicate. In the process of
self-replication, the number of objects doubles every cycle. This
exponential growth stands in sharp contrast to conventional materials
production, where doubling the amount of product requires twice the
production time. At present, this linear scaling poses a major
stumbling block for the fabrication of useful quantities of
microscopic objects with a sophisticated architecture, which are
needed for the next stages of micro- and nanotechnology.
In order to obtain self-replication, the researchers coat
micrometer-sized particles with short stretches of DNA, so-called
"sticky ends". Each sticky end consists of a particular sequence of
DNA building blocks and sticky ends with complementary sequences form
very specific bonds that are reversible. Below a certain temperature,
the particles recognize each other and bind together, while they
unbind again above that temperature. This enables a scheme in which
the particles spontaneously organize into an exact copy on top of a
template, which can then be released by elevating the temperature.
Scientists have used DNA-mediated interactions before, but it has
always been very difficult to bind only a subset of particles—usually,
either all particles or no particles are bound. This makes it
challenging to make well-defined structures. Therefore, the NYU team,
comprised of researchers in the Physics Department's Center for Soft
Matter Research and in the university's Department of Chemistry,
sought to find a method to better control the interactions and
organization of the particles.
To do so, the researchers took advantage of the ability of certain DNA
sequences to fold into a hairpin-like structure or to bind to
neighboring sticky ends on the same particle. They found that if they
lowered the temperature very rapidly, these sticky ends fold up on the
particle—before they can bind to sticky ends on other particles. The
particles stuck only when they were held together for several
minutes—a sufficient period for the sticky ends to find a binding
partner on another particle.
"We can finely tune and even switch off the attractions between
particles, rendering them inert unless they are heated or held
together—like a nano-contact glue," said Mirjam Leunissen, a
post-doctoral fellow in the Center for Soft Matter Research and the
study's lead author.
To maneuver the particles, the team used optical traps, or tweezers.
This tool, created by David Grier, chair of NYU's Department of
Physics and one of the paper's authors, uses laser beams to move
objects as small as a few nanometers, or one-billionth of a meter.
The work has a range of possible applications. Notably, because the
size of micrometer-scale particles—approximately one-tenth the
thickness of a strand of human hair—is comparable to the wavelength of
visible light, ordered arrays of these particles can be used for
optical devices. These include sensors and photonic crystals that can
switch light analogous to the way semi-conductors switch electrical
currents. Moreover, the same organizational principles apply to
smaller nanoparticles, which possess a wide range of electrical,
optical, and magnetic properties that are useful for applications.
The work was supported by the National Science Foundation's Materials
Research Science and Engineering Center (MRSEC) program, the Keck
Foundation, and the Netherlands Organization for Scientific Research.
Adapted from materials provided by New York University, via
EurekAlert!, a service of AAAS.
ScienceDaily (June 16, 2009) — Researchers at New York University have
created a method to precisely bind nano- and micrometer-sized
particles together into larger-scale structures with useful materials
properties. Their work, which appears in the latest issue of the
journal Nature Materials, overcomes the problem of uncontrollable
sticking, which had been a barrier to the successful creation of
stable microscopic and macroscopic structures with a sophisticated
architecture.
The long-term goal of the NYU researchers is to create non-biological
materials that have the ability to self-replicate. In the process of
self-replication, the number of objects doubles every cycle. This
exponential growth stands in sharp contrast to conventional materials
production, where doubling the amount of product requires twice the
production time. At present, this linear scaling poses a major
stumbling block for the fabrication of useful quantities of
microscopic objects with a sophisticated architecture, which are
needed for the next stages of micro- and nanotechnology.
In order to obtain self-replication, the researchers coat
micrometer-sized particles with short stretches of DNA, so-called
"sticky ends". Each sticky end consists of a particular sequence of
DNA building blocks and sticky ends with complementary sequences form
very specific bonds that are reversible. Below a certain temperature,
the particles recognize each other and bind together, while they
unbind again above that temperature. This enables a scheme in which
the particles spontaneously organize into an exact copy on top of a
template, which can then be released by elevating the temperature.
Scientists have used DNA-mediated interactions before, but it has
always been very difficult to bind only a subset of particles—usually,
either all particles or no particles are bound. This makes it
challenging to make well-defined structures. Therefore, the NYU team,
comprised of researchers in the Physics Department's Center for Soft
Matter Research and in the university's Department of Chemistry,
sought to find a method to better control the interactions and
organization of the particles.
To do so, the researchers took advantage of the ability of certain DNA
sequences to fold into a hairpin-like structure or to bind to
neighboring sticky ends on the same particle. They found that if they
lowered the temperature very rapidly, these sticky ends fold up on the
particle—before they can bind to sticky ends on other particles. The
particles stuck only when they were held together for several
minutes—a sufficient period for the sticky ends to find a binding
partner on another particle.
"We can finely tune and even switch off the attractions between
particles, rendering them inert unless they are heated or held
together—like a nano-contact glue," said Mirjam Leunissen, a
post-doctoral fellow in the Center for Soft Matter Research and the
study's lead author.
To maneuver the particles, the team used optical traps, or tweezers.
This tool, created by David Grier, chair of NYU's Department of
Physics and one of the paper's authors, uses laser beams to move
objects as small as a few nanometers, or one-billionth of a meter.
The work has a range of possible applications. Notably, because the
size of micrometer-scale particles—approximately one-tenth the
thickness of a strand of human hair—is comparable to the wavelength of
visible light, ordered arrays of these particles can be used for
optical devices. These include sensors and photonic crystals that can
switch light analogous to the way semi-conductors switch electrical
currents. Moreover, the same organizational principles apply to
smaller nanoparticles, which possess a wide range of electrical,
optical, and magnetic properties that are useful for applications.
The work was supported by the National Science Foundation's Materials
Research Science and Engineering Center (MRSEC) program, the Keck
Foundation, and the Netherlands Organization for Scientific Research.
Adapted from materials provided by New York University, via
EurekAlert!, a service of AAAS.
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