National Science Foundation     |     Directorate for Engineering  (ENG)
Division of Chemical, Bioengineering, Environmental, & Transport Systems  (CBET)
CBET Award Achievements  (Formerly "CBET Nuggets")
Notable Accomplishments from CBET Awards
Collaborative Research:  Locking Nanoparticles
Sergiy Minko  -  Clarkson University
Igor Luzinov  -  Clemson University

Collaborators at Clarkson University in New York and Clemson University in South Carolina are developing superparamagnetic nanoparticles whose properties can be switched on and off through external stimuli so that they can be used in a range of biological and medical applications.  This is important for applications where the adsorption of particles on various surfaces needs to be turned on and off during various stages of a process.

Background:  There is rapidly increasing interest in nanoparticles used as delivery vehicles in various biological and medical applications, for stabilization of emulsions and foams, and regulation of rheological and optical properties of suspensions.  All the applications are related to well-controlled interactions between neighboring nanoparticles as well as between nanoparticles and their host environment.  Significant advances in the development of the fundamental background for the understanding of particle behavior and in applications of the nanoparticles and their assemblies in modern technologies rely on the extension of the particles' behavior toward stimuli responsive properties using light, magnetic fields and electrical fields.  Nanoparticles with tunable interparticle interactions can be used for reorganization of particles (aggregation/disaggregation, adsorption/desorption, stabilization/destabilization of emulsions, inversion of emulsions) upon chemical changes in their environment and/or exposure to external fields.  These materials will create new opportunities to regulate and control behavior in complex "intelligent" systems and could be useful for many technologies and processes such as separation, mass transport, medical diagnostics, drug delivery systems, coatings, and sensors.

Results:  The research teams at Clarkson University in New York and Clemson University in South Carolina have developed a novel method for the surface modification of magnetic nanoparticles with an amphiphilic diblock copolymer.  This method resulted in the synthesis of nanoparticles which can be self-assembled into rod-like structures upon "magnetic click" - a pulse of external magnetic field.  Upon the magnetic signal the rod-like structures are locked and remain unchanged in aqueous dispersions with no external magnetic field.  However, the rod-like structures can be unlocked and the particles can be disassembled upon other external signals (for example, by adding an acidic solution).  This intelligent behavior of the nanoparticles controlled by external signals could find a broad range of important applications in various technologies from magnetic fluids to biotechnologies and medicine.

Sergiy Minko Image
Figure 1.  Interactions between magnetic hybrid nanoparticles (coated with an amphiphilic copolymer) in a magnetic field in a controlled aqueous environment:
(ASteric repulsive forces of blue polymer chains stabilize magnetic nanoparticles in aqueous dispersions
(BSelf-assembly and locking of the nanoparticles in an external magnetic field due to hydrophobic interactions between the inner particle shell formed by hydrophobic polyelectrolyte polymeric blocks; the particles are locked in the secondary minimum of the potential energy of interparticle interactions; exposure of the dispersion to a pulse of an external magnetic field yields rod-like structures (AFM topographical image on the right)
(CChanges in the pH of the particle dispersion switch off the particles interactions due to electrostatic repulsion of protonated polyelectrolyte in the inner shell; the particles undergo a transition from the secondary minimum to the repulsive mode (AFM image on the left).  The particles can be returned to the initial stage by reversible changes in the inner shell
(DThe plot demonstrates the effect of pH and an external magnetic field on the hydrodynamic diameter of the hybrid nanoparticles.
Image Credit:  Sergiy Minko (Clarkson University) and
                    Igor Luzinov (Clemson University)

Scientific Uniqueness:  The developed magnetic material has been previously unavailable.  The known magnetic liquids form self-assembled structures in a magnetic field.  Integrity of the structures is preserved only by the external magnetic field and, thus, by consumption of energy.  The ability of the newly developed materials to form and stabilize the structure by a pulse of a magnetic field is unique.

This project addresses the NSF Strategic Outcome Goals, as described in the NSF Strategic Plan 2006-2011, as follows:
Primary Strategic Outcome Goal:      (1) Discovery:  This research has discovered a novel kind of magnetic dispersions with unique stimuli-responsive properties.

                                                                   (1) Discovery Category:
                                                                           -  Engineering

Secondary Strategic Outcome Goal:  (2) Learning:  The project involves training and research of undergraduate students, graduate students and post-docs.  They have received training in synthesis and characterization of nanoparticles, utilization of the polymers for surface modification of nanoparticles, polymer grafting, light scattering, and atomic force microscopy.  In general the project helps strengthen the training of students in the areas of magnetic nanoparticles and surface science.  The project provides ample opportunities to integrate research and education through the cross-disciplinary student training in research labs, and scientific seminars.  The results from the project will be incorporated into undergraduate and graduate classes taught by PIs.

                                                                   (2) Learning Categories:
                                                                           -  Undergraduate Education and Undergraduate Student Research
                                                                           -  Graduate Education and Graduate Student Research
                                                                           -  Postdoctoral Education and Fellowships

This Award Achievement represents potentially Transformative Research:  The developed novel materials have promising applications in engineering, biotechnology and medicine.  In the long term, the proposed magnetic material could serve as a platform for the development of a wide range of new energy-efficient functional materials, processes and devices which explore the discovered locking mechanism for colloidal dispersions of the hybrid magnetic nanoparticles.

The Intellectual Merit of this research:  This particular proposal is focused on responsive nanoparticles capable of reorganization in an external magnetic field, which can turn on interactions between the particles themselves or between particles and their environment.  The interaction remains unchanged even after removal of the external magnetic field due to the specially tailored polymer shell of the nanoparticles.  This mechanism is termed here the "locking mechanism."  The "locking particles" can be unlocked by applying external stimuli such as temperature, changes in pH, chemical reaction, or strong shear forces.

The Broader Impacts of this research include:
(1Broadening participation of underrepresented groups:  The project involves training and research of female students in the area of chemical engineering.
(2Benefits of the proposed activity to society:  The obtained results are expected to have substantial impact on nanoscience and nanotechnology fields involving nanoparticle technologies and design of complex energy-efficient functional materials and devices.  The magnetic responsive particles will be used for a range of important medical and technical applications where the specific versus nonspecific particle interactions can be switched on in the external magnetic field.  The project has an important educational role for training undergraduate and graduate students.
(3Advancing discovery and understanding while promoting teaching, training, and learning:  In general the project helps strengthen the training of students in the areas of colloid and surface science.  The project provides opportunities to integrate research and education through cross-disciplinary student training in research labs, and scientific seminars.  The PIs involve both undergraduate and graduate students in the proposed research and train them to gain:
      (i)   expertise in nanofabrication techniques,
      (ii)  familiarity with modern concepts in materials and colloidal chemistry,
      (iii)  the ability to synthesize and characterize nano-materials,
      (iv) the ability to run experiments, gather data, and make discoveries, and
      (v)  the ability to write scientific papers and make effective technical presentations.
(4Broadening participation of underrepresented groups:  The project involves training and research of female students in the area of chemical engineering.
(5Disseminaton of results to enhance scientific and technological understanding:  The work of this research group appeared in the journal Nature Nanotechnology, which has a very broad readership and high impact factor.  In addition, the PIs have given research overviews and general seminars on sustainability and energy to the public to foster an understanding of the issues involved in finding future alternatives for petroleum-based fuels.  These have included, but are not limited to, presentations to the local Rotary Club, local high school, and University Pre-Game Scholar Showcase and the Centripetals Seminar Series, which are promoted as scholarly presentations targeted to and heavily subscribed by the general population.

Areas of Emphasis (Themes) for FY 2010 Highlights included in this research project:
(1Interdisciplinary, high-risk, and potentially transformative
(2Speeds the translation of promising fundamental research into innovations that can be commercialized
(3Promotes innovative energy technologies
(4Enhances health and quality of life
(5Advances new materials and devices -- such as silicon microelectronics that exploit properties at the quantum level required to realize computing capacity beyond the limits suggested by Moore's Law (SEBML)

Program Director:
Marc Ingber
CBET Program Director - Particulate and Multiphase Processes
NSF Award Number:   0756461
Award Title:   Collaborative Research: Locking Nanoparticles
PI Name:    Sergiy Minko
Institution Name:   Clarkson University;  Potsdam, NY
Program Element Code:   1415
CBET Award Achievement:

  FY 2010

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This Award Achievement was Updated on 5 October 2010.