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Benjamin Shapiro
Fischell Department of Bioengineering
Joint appointment with:
Institute for Systems Research
2246 Kim Building
University of Maryland
College Park, MD 20742
Tel: (301) 405-4191
Fax: (301) 405-9953

Particles are trapped and steered by feedback control. 1) The actual position of the particles is sensed and compared to the desired positions. 2) A correcting flow and/or electric field is computed, and then actuated, this field moves all the particles from where they are to closer to where they should be. 3) The process repeats at each time to achieve particle trapping or steering.

Figure 1
Figure 1: Feedback control particle steering approach for a single particle. A micro-fluidic device with standard electroosmotic actuation is observed by a vision system that informs the control algorithm of the current particle position. The control algorithm compares the actual position against the desired position and finds the actuator voltages that will create a fluid flow, at the particle location, to steer the particles from where it is to where it should be. The process repeats continuously to steer the particle along its desired path. (Figure and caption taken from [ Armani06 ].

Both our work (Shapiro et al. [Shapiro2002], [Armani04], [ArmaniFeb05], [Armani Mar05], [ArmaniNov05], [Chaudhary06], [Armani06]) and the ‘ABEL trap’ work of Cohen and Moerner at Stanford ([Cohen04], [CohenFeb05], [CohenMar05], [CohenMar05a], [CohenMar05b], [CohenAug05], [CohenAug06]), uses feedback control to trap and steer one or multiple particles (us) or just one particle (Cohen, Moerner).

We did this first (in 2002 [Shapiro2002]). Subsequently, and to our best knowledge independently, Cohen and Moerner came up with their concept in 2004 (two years later [Cohen04]).

Click on the boxes in the timeline below to view available documents.

Figure 2: Timeline. Relevant dates are shown: submission dates for patents and publications (presentation) dates for journal papers (conferences). (Unpublished disclosures are shown in the dashed line boxes.) We did not submit a journal paper until we had demonstrated control of multiple particles at once, which includes an ability to control one particle individually.

We are focused on manipulation of objects (e.g. cells) in cheap micro-fluidic (PDMS or glass) devices, we can steer multiple particles at once to 1 mm accuracy (this accuracy is set by the optical resolution of our microscope). We have developed sophisticated and robust control algorithms to achieve our goals. Cohen and Moerner are focused on single molecule spectroscopy, they can trap and steer only one particle using a simple control scheme. But they can do so with higher accuracy (80 nm) based on their better optical resolution, which they achieve by using a more expensive microscope or by sensing the output of a rotating laser beam (this laser sensing scheme is new/novel compared to our work -- it was first proposed by Joerg Enderlein, then first implemented by Enrico Gratton, and taken to the shot-noise limit and expanded to single quantum dot tracking in 3D by Berglund, McHale, and Mabuchi http://minty.caltech.edu/Tracking/.

If you believe that any statements on this page are factually incorrect, please send me an email to benshap@eng.umd.edu along with a brief explanation plus attached documentation. If there are any factual errors, I will correct them.

In chronological order: from first to last. Blue for our work, green for Cohen/Moerner.

Shapiro 2002: B.Shapiro, S.Chaudhary*, M.Armani*, R.Probst* “Arbitrary and Simultaneous Control of Multiple Particles in Micro-Fluidic Systems”. Invention of disclosure submitted to Univ. of Maryland Office of Commercialization on 14 December 2002. Recorded at Univ. of MD on 7 January 2003. Provisional patent filed 5 September 2003. Utility patent filed 5 Sept 2004 (patent no. 20050051429).
As a [PDF file] that includes patent figures.
Chaudhary 03: S.Chaudhary*, B.Shapiro, “Arbitrary Control of Multiple Particles in a Microfluidic Device”, International Mechanical Engineering Congress and Exposition, Washington DC, 16-21 Nov 2003. [No publication, oral presentation only.]
Shapiro 04: B. Shapiro, “Flow Control on the Micro-Scale for Bio-Chemical Sensing and Actuation”, 42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 5-8 Jan 2004. [No publication, oral presentation only.]
Cohen 04: A.E. Cohen, W. E. Moerner Method and apparatus for manipulating
nanoscale objects in solution, US patent pending. Provisional patent
filed 20 Aug 2004, full patent filed Aug 2005.
23 Aug 04:
A. E. Cohen, W. E. Moerner, "Active feedback electrophoresis: a new way to trap and manipulate small objects," Fifth International Conference on Biological Physics ICBP2004, Gothenburg, Sweden, August 23-27, 2004, no publication, poster presentation."
Armani 04: M.Armani*, S.Chaudhary*, R.Probst*, B.Shapiro, “Micro Flow Control Particle Tweezers”, mTAS 2004, Malmo, Sweden, 26-30 September 2004.
Armani Feb05: M.Armani*, S.Chaudhary*, R.Probst*, B.Shapiro, “Using Feedback Control and Micro-Fluidics to Steer Individual Particles”, MEMS 2005, pg 855-858, Miami, Florida. 30 Jan to 3 Feb, 2005.
Cohen Feb05: A.E. Cohen and W. E. Moerner “Method for Trapping and Manipulating Nanoscale Objects in Solution”, Appl. Phys. Lett. 86, 093109, Feb. 28 2005.
Armani Mar05: M.Armani*, S.Chaudhary*, R.Probst*, B.Shapiro, "Steering and
Trapping Multiple Particles by Feedback Flow Control: Theory and
Experiments", Applied Physics Society (APS) March meeting, Baltimore, MD, March 2006. [No publication, oral presentation only. Session organized by Dr. Moerner.]
Cohen Mar06: A.E. Cohen and W. E. Moerner “Suppressing Brownian motion of individual biomolecules in solution”, PNAS, 103, 4362-4365, 14 March 2006.
Cohen Mar05a: A.E. Cohen and W. E. Moerner “The Anti-Brownian Electrophoretic Trap (ABEL Trap): Fabrication and Software”, Proc. SPIE vol. 5699, Mar 2005.
Cohen Mar05b: A.E. Cohen “Control of nanoparticles with arbitrary two-dimensional force fields”, Phys. Rev. Lett., 94, 118102, Mar. 25 2005.
Cohen Aug05: A.E. Cohen and W. E. Moerner “An all-glass microfluidic cell for the ABEL trap: fabrication and modeling”, Proc. SPIE vol. 5930, Aug 2005
Armani Nov05: M.Armani, S.Chaudhary, R.Probst, S.Walker, B.Shapiro "Control of Micro-Fluidic Systems: Two Examples, Results, and Challenges" International Journal of Robust and Nonlinear Control, vol 15, issue 16, pg 785-803, 10 November 2005.
Chaudhary 06: S.Chaudhary, B.Shapiro "Arbitrary Steering of Multiple Particles Independantly in an Electroosmotically Driven Microfluidic System" IEEE Transactions on Control Systems Technology, vol 14, issue 4, pg 669-680, July 2006.
Armani 06: M.Armani, S.Chaudhary, R.Probst, B.Shapiro "Using Feedback Control of Micro-Flows to Independently Steer Multiple Particles" Journal of Microelectromechanical Systems (JMEMS), vol 15, no 4, pg 945-956, Aug 2006.
Cohen Aug06: A.E. Cohen “Trapping and Manipulating Single Molecules in Solution”, PhD Thesis, Stanford University, defended Aug. 2006.

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