Article

Triaxial AFM Probes for Noncontact Trapping and Manipulation

School of Engineering and Applied Sciences, and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States.
Nano Letters (Impact Factor: 13.59). 08/2011; 11(8):3197-201. DOI: 10.1021/nl201434t
Source: PubMed

ABSTRACT We show that a triaxial atomic force microscopy probe creates a noncontact trap for a single particle in a fluid via negative dielectrophoresis. A zero in the electric field profile traps the particle above the probe surface, avoiding adhesion, and the repulsive region surrounding the zero pushes other particles away, preventing clustering. Triaxial probes are promising for three-dimensional assembly and for selective imaging of a particular property of a sample using interchangeable functionalized particles.

1 Follower
 · 
95 Views
  • Source
    • "The use of a triaxial probe to generate a dielectrophoresis field that acts as a non-contact trap for dielectric nanoparticles has been recently demonstrated [12] [13]. This method is proposed to work for particles as small as 5 nm [13] and has been verified for the isolation of 100 nm polystyrene beads [12]. Although maintaining non-contact avoids potential problems with adhesive forces, the ultimate spatial positioning of targeted particles would be too inconsistent due to the randomizing effects of "
    [Show abstract] [Hide abstract]
    ABSTRACT: Techniques to reliably pick-and-place single nanoparticles into functional assemblies are required to incorporate exotic nanoparticles into standard electronic circuits. In this paper we explore the use of electric fields to drive and direct the assembly process, which has the advantage of being able to control the nano-assembly process at the single nanoparticle level. To achieve this, we design an electrostatic gating system, thus enabling a voltage-controllable nanoparticle picking technique. Simulating this system with the nonlinear Poisson-Boltzmann equation, we can successfully characterize the parameters required for single particle placement, the key being single particle selectivity, in effect designing a system that can achieve this controllably. We then present the optimum design parameters required for successful single nanoparticle placement at ambient temperature, an important requirement for nanomanufacturing processes.
    Nanotechnology 09/2013; 24(40):405304. DOI:10.1088/0957-4484/24/40/405304 · 3.67 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Controlled manipulation of individual micro- and nanoscale objects requires the use of trapping forces that can be focused and translated with high spatial and time resolution. We report a new strategy that uses the flow of mobile microvortices to trap and manipulate single objects in fluid with essentially no restrictions on their material properties. Fluidic trapping forces are generated toward the center of microvortices formed by magnetic microactuators, that is, rotating nanowire or self-assembled microbeads, actuated by a weak rotating magnetic field (|B|< 5 mT). We demonstrate precise manipulation of single microspheres and microorganisms near a solid surface in water.
    Nano Letters 11/2011; 12(1):156-60. DOI:10.1021/nl2032487 · 13.59 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Kelvin probe force microscopy (KPFM) is a widely used technique to measure the local contact potential difference (CPD) between an AFM probe and the sample surface via the electrostatic force. The spatial resolution of KPFM is intrinsically limited by the long range of the electrostatic interaction, which includes contributions from the macroscopic cantilever and the conical tip. Here, we present coaxial AFM probes in which the cantilever and cone are shielded by a conducting shell, confining the tip-sample electrostatic interaction to a small region near the end of the tip. We have developed a technique to measure the true CPD despite the presence of the shell electrode. We find that the behavior of these probes agrees with an electrostatic model of the force, and we observe a factor of five improvement in spatial resolution relative to unshielded probes. Our discussion centers on KPFM, but the field confinement offered by these probes may improve any variant of electrostatic force microscopy.
    Nanotechnology 03/2012; 23(11):115703. DOI:10.1088/0957-4484/23/11/115703 · 3.67 Impact Factor
Show more

Preview

Download
0 Downloads
Available from