R. Probst

Learn More
—In this paper, we show how to combine microfluidics and feedback control to independently steer multiple particles with micrometer accuracy in two spatial dimensions. The particles are steered by creating a fluid flow that carries all the particles from where they are to where they should be at each time step. Our control loop comprises sensing,(More)
Any single permanent or electro magnet will always attract a magnetic fluid. For this reason it is difficult to precisely position and manipulate ferrofluid at a distance from magnets. We develop and experimentally demonstrate optimal (minimum electrical power) 2-dimensional manipulation of a single droplet of ferrofluid by feedback control of 4 external(More)
We show how it is possible to combine micro-fluidics and feedback control (sense, compare, and apply corrective actuation) to steer many particles at once. The particles are steered by creating a spatially complex and time-varying fluid flow that carries all particles along their desired trajectories. We demonstrated experimental results for steering of a(More)
We present a method for manipulating preselected quantum dots (QDs) with nanometer precision by flow control. The accuracy of this approach scales more favorably with particle size than optical trapping, enabling more precise positioning of nanoscopic particles. We demonstrate the ability to position a single QD in a 100 microm working region to 45 nm(More)
We show how to extend electrokinetic tweezing (which can manipulate any visible particles and has more favorable force scaling than optical actuation enabling manipulation of nanoscale objects to nanoscopic precision) from two-dimensional control to the third dimension (3D). A novel and practical multi-layer device is presented that can create both planar(More)
We demonstrate a technique for the precise immobilization of nanoscale objects at accurate positions on two-dimensional surfaces. We have developed a water-based photoresist that causes nanostructures such as colloidal quantum dots to segregate to a thin layer at surfaces. By combining this material with electroosmotic feedback control, we demonstrate the(More)
We present a comprehensive theory of closed-loop particle tracking for calculating the statistics of a diffusing fluorescent particle's motion relative to the tracking lock point. A detailed comparison is made between the theory and experimental results, with excellent quantitative agreement found in all cases. A generalization of the theory of (open-loop)(More)
We show how to steer many particles at once in a micro fluidic chamber by generating the correct time-varying flow fields using electroosmotic actuation. The basic idea is shown in Figure 1: we fabricate a planar micro fluidic device with an array of electrodes which create electric fields that can move the flow by electroosmotic forces [1]; the resulting(More)
PURPOSE A time-varying magnetic field can cause unpleasant peripheral nerve stimulation (PNS) when the maximum excursion of the magnetic field (ΔB) is above a frequency-dependent threshold level [P. Mansfield and P. R. Harvey, Magn. Reson. Med. 29, 746-758 (1993)]. Clinical and research magnetic resonance imaging (MRI) gradient systems have been designed to(More)
  • Micheal Armani, Satej Chaudhary, Roland Probst, Shawn Walker, Benjamin Shapiro
  • 2005
1. Abstract This paper describes results and challenges in feedback control of microfluidic systems. Results are provided for two representative examples: control of liquid droplets by electrically actuated surface tension forces and steering of many particles at once by micro flow control. Common themes and challenges are outlined based on the authors(More)