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| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editors: Andrew Dunn and Anthony Durkin
  • Vol. 8, Iss. 1 — Feb. 4, 2013
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Acousto-optically generated potential energy landscapes: Potential mapping using colloids under flow

Michael P. N. Juniper, Rut Besseling, Dirk G. A. L. Aarts, and Roel P. A. Dullens  »View Author Affiliations


Optics Express, Vol. 20, Issue 27, pp. 28707-28716 (2012)
http://dx.doi.org/10.1364/OE.20.028707


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Abstract

Optical potential energy landscapes created using acousto-optical deflectors are characterized via solvent-driven colloidal particles. The full potential energy of both single optical traps and complex landscapes composed of multiple overlapping traps are determined using a simple force balance argument. The potential of a single trap is shown to be well described by a Gaussian trap with stiffness found to be consistent with those obtained by a thermal equilibrium method. We also obtain directly the depth of the well, which (as with stiffness) varies with laser power. Finally, various complex systems ranging from double-well potentials to random landscapes are generated from individually controlled optical traps. Predictions of these landscapes as a sum of single Gaussian wells are shown to be a good description of experimental results, offering the potential for fully controlled design of optical landscapes, constructed from single optical traps.

© 2012 OSA

1. Introduction

Undulating potential energy landscapes appear in a vast range of physical systems, from the surfaces in atomic crystals [1

1. E. Gnecco, R. Bennewitz, T. Gyalog, Ch. Loppacher, M. Bammerlin, E. Meyer, and H.-J. Güntherodt, “Velocity Dependence of Atomic Friction,” Phys. Rev. Lett. 84, 1172–1175 (2000). [CrossRef] [PubMed]

] to Josephson junctions in superconductors [2

2. K. E. Kürten and C. Krattenthaler, “Multistability and multi 2π-kinks in the Frenkel-Kontorova model: an application to arrays of Josephson Junctions,” Int. J. Mod. Phys. B 21, 2324–2334 (2007). [CrossRef]

]. Modeling such landscapes has become an important challenge in science and engineering as many devices and electronic systems become smaller and their features become more difficult to probe directly [3

3. V. K. Vlasko-Vlasov, A. E. Koshelev, U. Welp, W. Kwok, A. Rydh, G. W. Crabtree, and K. Kadowaki, “Magneto-optical imaging of Josephson vortices in layered superconductors,” in Magneto-Optical Imaging, T. H. Johansed and D. V. Shantsev, eds. (Springer, 2004), pp. 39–46. [CrossRef]

]. Model potential energy landscapes have been created with a wide range of techniques varying from directly structuring surfaces using lithographic techniques [4

4. B. Michel, A. Bernard, A. Bietsch, E. Delamarche, M. Geissler, D. Juncker, H. Kind, J.-P. Renault, H. Rothuizen, H. Schmid, P. Schmidt-Winkel, R. Stutz, and H. Wolf, “Printing meets lithography: Soft approaches to high-resolution patterning,” IBM J. Res. & Dev. 45, 697–719 (2001). [CrossRef]

6

6. G. Zhang and D. Wang, “Colloidal Lithography - The Art of Nanochemical Patterning,” Chem. Asian J. 4, 236–245 (2009). [CrossRef]

] to selectively adsorbing nanoparticles to surfaces [7

7. A. J. O’Reilly, C. Francis, and N. J. Quitoriano, “Gold nanoparticle deposition on Si by destabilising gold colloid with HF,” J. Colloid Interf. Sci. 370, 46–50 (2012). [CrossRef]

].

The discovery of optical trapping of small particles using tightly focused laser light by Ashkin [8

8. A. Ashkin, “Acceleration and trapping of particles by radiation pressure,” Phys. Rev. Lett. 24, 156–159 (1970). [CrossRef]

] opened the field of optical manipulation, offering the possibility of generating potential energy landscapes using light. Optical landscapes have proved very versatile, addressing problems ranging from particle sorting [9

9. P. T. Korda, M. B. Taylor, and D. G. Grier, “Kinetically locked-in colloidal transport in an array of optical tweezers,” Phys. Rev. Lett. 89, 128301 (2002). [CrossRef] [PubMed]

12

12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

], phase behaviour [13

13. C. Bechinger, M. Brunner, and P. Leiderer, “Phase Behavior of Two-Dimensional Colloidal Systems in the Presence of Periodic Light Fields,” Phys. Rev. Lett. 86, 930–934 (2001). [CrossRef] [PubMed]

] and Kramer’s hopping [14

14. D. Babic, C. Schmitt, I. Poberaj, and C. Bechinger, “Stochastic resonance in colloidal systems,” Europhys. Lett. 67, 158–164 (2004). [CrossRef]

17

17. A. Curran, M. P. Lee, R. Di Leonardo, J. M. Cooper, and M. J. Padgett, “Partial synchronization of stochastic oscillators through hydrodynamic coupleing,” Phys. Rev. Lett. 108, 240601 (2012). [CrossRef] [PubMed]

] to nanotribology [18

18. T. Bohlein, J. Mikhael, and C. Bechinger, “Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces,” Nat. Materials 11, 126–130 (2012). [CrossRef]

, 19

19. T. Bohlein and C. Bechinger, “Experimental observation of directional locking and dynamical ordering of colloidal monolayers driven across quasiperiodic substrates,” Phys. Rev. Lett. 109, 058301 (2012). [CrossRef] [PubMed]

]. For all of these applications a detailed knowledge of the potential energy landscape is crucial. In laser based particle sorting techniques for instance, the efficiency depends sensitively on the deflection angle, whose optimum may be predicted from the details of the landscapes [9

9. P. T. Korda, M. B. Taylor, and D. G. Grier, “Kinetically locked-in colloidal transport in an array of optical tweezers,” Phys. Rev. Lett. 89, 128301 (2002). [CrossRef] [PubMed]

12

12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

].

Optical potential energy landscapes, U(x), are generally characterized as a function of position, x, by inverting the probability distribution, P(x), of Brownian particles in the landscape using Boltzmann’s factor P(x) ∝ exp [−βU(x)] [13

13. C. Bechinger, M. Brunner, and P. Leiderer, “Phase Behavior of Two-Dimensional Colloidal Systems in the Presence of Periodic Light Fields,” Phys. Rev. Lett. 86, 930–934 (2001). [CrossRef] [PubMed]

, 15

15. C. Schmitt, B. Dybiec, P. Hänggi, and C. Bechinger, “Stochastic resonance vs. resonant activation,” Europhys. Lett. 74, 937–943 (2006). [CrossRef]

17

17. A. Curran, M. P. Lee, R. Di Leonardo, J. M. Cooper, and M. J. Padgett, “Partial synchronization of stochastic oscillators through hydrodynamic coupleing,” Phys. Rev. Lett. 108, 240601 (2012). [CrossRef] [PubMed]

, 20

20. K. C. Neuman and S. M. Block, “Optical trapping,” Rev. Sci. Instrum. 75, 2787 (2004). [CrossRef]

, 21

21. J. Dobnikar, M. Brunner, H. H. von Grünberg, and C. Bechinger, “Three-body interactions in colloidal systems,” Phys. Rev. E 69, 031402 (2004). [CrossRef]

], where β = (kBT)−1 with kB Boltzmann’s constant and T the absolute temperature. However, with thermal fluctuations being the motive force this approach is typically limited to optical potentials with a depth, U0, of a few kBT. Also, characterizing single optical traps by this method leads to the restoring force, Fopt = −kx, of a harmonic optical potential [20

20. K. C. Neuman and S. M. Block, “Optical trapping,” Rev. Sci. Instrum. 75, 2787 (2004). [CrossRef]

, 21

21. J. Dobnikar, M. Brunner, H. H. von Grünberg, and C. Bechinger, “Three-body interactions in colloidal systems,” Phys. Rev. E 69, 031402 (2004). [CrossRef]

], where k is the trapping stiffness and x the displacement of a particle from the center of the trap. This linear regime is generally sufficient in the limit of small fluctuations, but breaks down for larger displacements [22

22. A. C. Richardson, S. N. S. Reihani, and L. B. Oddershede, “Non-harmonic potential of a single beam optical trap,” Opt. Express 16, 15709–15717 (2008). [CrossRef] [PubMed]

24

24. M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett. 36, 1260–1262 (2011). [CrossRef] [PubMed]

]. This is particularly important for non-equilibrium optical trapping applications such as active micro-rheology [25

25. R. R. Brau, J. M. Ferrer, H. Lee, C. E. Castro, B. K. Tam, P. B. Tarsa, P. Matsudaira, M. C. Boyce, R. D. Kamm, and M. J. Lang, “Passive and active microrheology with optical tweezers,” J. Opt. A: Pure Appl. Opt. 9, S103–S112 (2007). [CrossRef]

,26

26. M. Tassieri, G. M. Gibson, R. M. L. Evans, A. M. Yao, R. Warren, M. J. Padgett, and J. M. Cooper, “Measuring storage and loss moduli using optical tweezers: Broadband microrheology,” Phys. Rev. E 81, 026308 (2012). [CrossRef]

]; during the dragging of a trapped particle though a viscoelastic medium the particle is likely to sample the non-linear regions of an optical trap.

To characterize the full potential energy of single optical traps and deeper potential energy landscapes with wells of tens of kBT, driving forces up to typically a pico-Newton are required. Piezoelectric stages [22

22. A. C. Richardson, S. N. S. Reihani, and L. B. Oddershede, “Non-harmonic potential of a single beam optical trap,” Opt. Express 16, 15709–15717 (2008). [CrossRef] [PubMed]

, 23

23. T. Godazgar, R. Shokri, and S. N. Reihani, “Potential mapping of optical tweezers,” Optics Letters 36, 3284–3286 (2011). [CrossRef] [PubMed]

] and a dual-beam optical trap [24

24. M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett. 36, 1260–1262 (2011). [CrossRef] [PubMed]

] have been used to drive single trapped particles away from the trap center, and a stiffening of the optical trap has been observed. In the case of extended potential energy landscapes Arzola et. al. reported a study of a particle on an inclined plane, passing an optical washboard potential created by interference fringes [27

27. A. V. Arzola, K. Volke-Sepulveda, and J. L. Mateos, “Force mapping of an extended light pattern in an inclined plane: Deterministic regime,” Opt. Express 17, 3429–3440 (2009). [CrossRef] [PubMed]

]. This approach uses various particles on the order of 10 μm in diameter, such that gravity is a sufficient driving force for particles to escape individual traps. Further studies report particle sorting using the solvent driven flow of colloidal particles over optical landscapes created using interference patterns [10

10. M. P. MacDonald, G. C. Spalding, and K. Dholakia, “Microfluidic sorting in an optical lattice,” Nature 426, 421–424 (2003). [CrossRef] [PubMed]

], spatial light modulators (SLMs) [9

9. P. T. Korda, M. B. Taylor, and D. G. Grier, “Kinetically locked-in colloidal transport in an array of optical tweezers,” Phys. Rev. Lett. 89, 128301 (2002). [CrossRef] [PubMed]

, 12

12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

, 28

28. K. Ladavac, K. Kasza, and D. G. Grier, “Sorting mesoscopic objects with periodic potential landscapes: Optical fractionation,” Phys. Rev. E 70, 010901 (2004). [CrossRef]

, 29

29. M. J. Padgett and R. Di Leonardo, “Holographic optical tweezers and their relevance to lab on chip devices,” Lab Chip 11, 1196–1205 (2011). [CrossRef] [PubMed]

] and acousto-optical deflectors (AODs) [11

11. G. Milne, D. Rhodes, M. MacDonald, and K. Dholakia, “Fractionation of polydisperse colloid with acousto-optical generated potential energy landscapes,” Opt. Lett. 32, 1144–1146 (2007). [CrossRef] [PubMed]

].

Here, we combine acousto-optically generated ‘one dimensional’ (1D) optical potential energy landscapes with colloidal particles driven using a well-defined solvent flow to quantitatively characterize the full optical potential energy landscape. The particles are driven along an axis through the centers of the 2D circularly symmetric optical traps, resulting in a 1D potential measurement. The solvent flow gives a driving force up to tens of pico-Newtons, which, based on a simple force balance [12

12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

, 27

27. A. V. Arzola, K. Volke-Sepulveda, and J. L. Mateos, “Force mapping of an extended light pattern in an inclined plane: Deterministic regime,” Opt. Express 17, 3429–3440 (2009). [CrossRef] [PubMed]

], allows us to simultaneously measure the trapping stiffness, k, and the depth, U0, of the traps constituting the optical landscape. Compared to other driving methods based on piezoelectric stages [22

22. A. C. Richardson, S. N. S. Reihani, and L. B. Oddershede, “Non-harmonic potential of a single beam optical trap,” Opt. Express 16, 15709–15717 (2008). [CrossRef] [PubMed]

, 23

23. T. Godazgar, R. Shokri, and S. N. Reihani, “Potential mapping of optical tweezers,” Optics Letters 36, 3284–3286 (2011). [CrossRef] [PubMed]

] or dual optical trap arrangements [24

24. M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett. 36, 1260–1262 (2011). [CrossRef] [PubMed]

], our method is cheap and fast, and in addition flowing multiple single particles through the landscape allows us to gain good statistics.

We find that the magnitude of the trapping stiffness is linearly proportional to the laser power, I0, consistent with thermal equilibrium methods, although these methods are limited to relatively weak traps [20

20. K. C. Neuman and S. M. Block, “Optical trapping,” Rev. Sci. Instrum. 75, 2787 (2004). [CrossRef]

]. The depth of the optical trap, which is not accessible using thermal equilibrium methods, is also found to be proportional to I0[12

12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

, 16

16. R. D. L. Hanes, C. Dalle-Ferier, M. Schmiedeberg, M. C. Jenkins, and S.U. Egelhaaf, “Colloids in one dimensional random energy landscapes,” Soft Matter 8, 2714–2723 (2012). [CrossRef]

]. Finally we extend our measurements to more complex, periodic and aperiodic potentials, and show that we can fully control, engineer and predict the exact nature of optical potential energy landscapes.

The paper is organized as follows: in section 2 the theoretical basis of this work is laid out, followed by a description of the experimental methods in section 3. Section 4 discusses the results from experiments on single traps (section 4.1) and landscapes consisting of multiple traps (section 4.2). We make our conclusions in section 5.

2. Dynamics of particles driven over optical traps

Particles driven by solvent flowing at velocity, vflow, at low Reynolds numbers (Re) and high Péclet numbers (Pe), experience a driving force Fflow = ξvflow, where ξ = 6πηR is the friction coefficient of a spherical particle of radius R in a solvent of viscosity η[30

30. J. Happel and H. Brenner, Low Reynolds Number Hydrodynamics (Kluwer Academic Publishers, Dordrecht, The Netherlands, 1983).

]. Re is a ratio of inertial to viscous forces, so particles in this low Re system are governed by the viscosity of the solvent, while Pe is a ratio of advection and diffusion in a fluid, so particles in this high Pe system are governed by the overall motion of the fluid. The presence of an optical potential energy landscape introduces an additional force, Fopt (x), which depends on the position coordinate, x, and causes perturbations to the velocity of the particle. A particle’s velocity, v(x), under the influence of both of these effects is described by,
v(x)=vflow+Fopt(x)ξ.
(1)
Measuring this instantaneous velocity as a function of the position of the particle, x, thus provides a direct measure for the optical forces and hence the potential energy landscape.

3. Experimental methods

3.1. Colloidal model system and flow

The flow is generated by a micro-fluidics pump (Harvard PHD 2000 with milled glass syringes), connected via micro-fluidics tubing to a quartz glass sample cell (Hellma) with a 200 μm vertical cross section (see Fig. 1(c)). The cell is cleaned between fills using 2% Hellmanex solution, rinsing with 20% EtOHaq, and plasma treatment. The particles used are Dynabeads® M-270 Carboxylic Acid, diameter σ = 2.8μm. These particles are highly monodisperse crosslinked polystyrene spheres with CO2H surface groups, making the particles negatively charged, and causing them to repel the negatively charged glass wall of the sample cell, preventing sticking. Because the particles have a high density, 1.6g cm−3, and consequently small gravitational height, ( hg=kBTm*g~0.01σ, where m* is the buoyant mass of the particle and g is gravitational field strength), the system is considered to be two-dimensional. Hence, in the presence of flow the particles follow a well defined one dimensional trajectory. We use very dilute suspensions of particles and consider a single particle driven through the potential.

Fig. 1 (a) Diagram of optical setup (not to scale); see also text in section 3.2. (b) Typical experimental image (cropped from the full CMOS chip) indicating the particle trajectory and the extent and position of the optical trap as indicated by the dotted lines. The corresponding graph of the particle velocity against position for one data set is also shown. (c) Diagram of sample cell.

3.2. Optical setup

The one-dimensional optical potential energy landscapes are generated by acousto-optically controlled optical laser tweezers [14

14. D. Babic, C. Schmitt, I. Poberaj, and C. Bechinger, “Stochastic resonance in colloidal systems,” Europhys. Lett. 67, 158–164 (2004). [CrossRef]

]. Figure 1 illustrates the optical setup used in this work. A 1064 nm laser beam (Coherent Compass) is expanded by two lenses (T1, T2), reflected by a mirror (M1), and directed through a pair of perpendicular acousto-optical deflectors (AODs, AA Opto-electronics). The AODs produce four output beams, of which one, the (1,1) order, is selected for further use, as it is deflected both horizontally and vertically. The beam is guided through the telescope optics, lenses T3 and T4, and redirected (M2 – M5) into the back aperture of a vertically positioned tweezing objective (Leica, 50x, NA=0.55), which focuses the beam to a waist of ∼ 2μm. The optical traps are controlled via the AODs using Aresis software [34

34. Aresis d.o.o., Aresis beam steering controller and Tweez software (2007).

].

3.3. Flow measurements

3.4. Equilibrium trap measurements

One of the traditional methods for finding the stiffness constant of an optical trap involves taking a long time series of a Brownian particle held by an optical trap [20

20. K. C. Neuman and S. M. Block, “Optical trapping,” Rev. Sci. Instrum. 75, 2787 (2004). [CrossRef]

]. The images obtained may then be analyzed by fitting a parabolic potential to a plot of probability against position. This method was used to compare to the data obtained from the flow method. To this end, a particle was placed in the optical trap previously used for the flow experiments, and images recorded at 2 fps for up to an hour.

4. Results and discussion

4.1. Single optical traps

Firstly, we drive the colloidal particles at ∼ 15μm s−1 along a linear path, running through the center of a single optical trap. Figure 2a shows the position of the particle as a function of time as obtained from the tracking routines. The early and late parts of the position versus time graph are linear and of the same gradient, indicating the particle traveling at the imposed flow velocity far away from the optical trap. When the particle travels through the optical trap its velocity is affected and a characteristic position-time pattern is observed, indicated in Fig. 2a by the markers A to D. The corresponding velocity versus position graph is shown in Fig. 2b. Initially the particle proceeds at the constant velocity of the solvent flow, until point A, when there is a period of acceleration due to gradient forces of the optical trap. The velocity then rapidly drops to its minimum at C, where the gradient force now opposes the flow forces. Beyond this point, the particles accelerates to reach the flow velocity at D.

Fig. 2 Typical experimental data as obtained from flow experiments for single optical traps. (a) The particle position as a function of time: ○ experimental data; solid lines are linear fits of equal gradient, indicating that the particle velocity equals the flow velocity before and after the optical trap. The right panel shows the corresponding potential, U(x). (b) The particle velocity v(x) as a function of the position; ○ experimental data; the solid line is a fit based on a Gaussian optical trap according to Eq. (4). The top panel again shows U(x).

Assuming a Gaussian potential for the optical trap (Eq. (2)), we fit the experimental data according to Eq. (4) to obtain the complete optical potential, fully characterised by the trapping stiffness, k, and the depth of the optical trap, U0. The solid curve in Fig. 2b, v(x), shows that this assumption is valid, and that the region of influence of the trap is around 10μm. We also show U(x) in Figs. 2a and 2b for completeness. The velocity profile in Fig. 2b is also a direct measure for the force profile (see Eq. (1)) and can be directly compared to earlier work which reported a stiffening of the potential at larger displacements [22

22. A. C. Richardson, S. N. S. Reihani, and L. B. Oddershede, “Non-harmonic potential of a single beam optical trap,” Opt. Express 16, 15709–15717 (2008). [CrossRef] [PubMed]

24

24. M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett. 36, 1260–1262 (2011). [CrossRef] [PubMed]

]. Our velocity profile appears very similar to the force profile reported in [23

23. T. Godazgar, R. Shokri, and S. N. Reihani, “Potential mapping of optical tweezers,” Optics Letters 36, 3284–3286 (2011). [CrossRef] [PubMed]

, 24

24. M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett. 36, 1260–1262 (2011). [CrossRef] [PubMed]

], although the uncertainty in our data does not allow us to resolve the expected stiffening of the trap, which would appear between points B and C as a deviation from the derivative of a Gaussian potential.

Fig. 3 (a) The trapping stiffness k (○ flow measurements; • thermal equilibrium measurements) and (b) the depth of the optical trap U0 as a function of the laser power. The solid lines are linear fits to the data.

4.2. Optical potential energy landscapes

We now extend our measurements to 1D potential energy landscapes generated by multiple overlapping single optical traps. This introduces additional contributions to the optical force exerted on the particle. Completely analogously to the single trap experiments, we use the velocity profile v(x) to reconstruct the potential energy landscape using Eq. (4). We will show that once the trap stiffness kj and well depth U0,j of the single optical traps are known, optical landscapes can be fully engineered and described by a simple sum of single Gaussian potentials as given by Eq. (3) [12

12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

].

First we consider a simple ‘extended’ landscape consisting of two pairs of identical optical traps. Figure 4a shows the velocity profile v(x) of a particle driven at a flow velocity of ∼ 11μm s−1 through four optical traps separated by distances δ12 = δ34 = 3μm and δ23 = 10μm. This arrangement is well described by four Gaussian wells (Eq. (4)), exhibiting additional small peaks in between the two traps constituting the pairs, which clearly illustrates the additivity of the potentials. Fitting may be achieved using the same parameters for each trap or independent parameters: we found the results from both methods to be within 3.5% of each other. The good correlation of the reconstructed potential energy landscape to that predicted by Eq. (3) (Fig. 4a, top panel) shows that the velocity profile in Fig. 4a corresponds to two double-well potentials separated by δ23 + 0.5 (δ12 + δ34) = 13μm.

Fig. 4 The particle velocity v(x) as a function of the position x when driven at a flow velocity of ∼ 11 μm s−1 through two different optical landscapes, where δij is the distance between traps i and j: (a) two pairs of overlapping optical traps positioned at δ12 = δ34 = 3μm and δ23 = 10μm. ○ experimental data, — is a fit according to Eq. (4). (b) Four traps with spacing δ = 3μm. ○ experimental data, - - - is a fit according to Eq. (4), — is a sinusoidal fit. The top panels in (a) and (b) show a comparison between the potentials, U(x), as obtained from the experiments (—) and predicted by Eq. (3) (□).

Finally, we generate two types of random potential energy landscapes consisting of overlapping optical traps with randomly generated positions and/or intensities (Fig. 5). In Fig. 5a we show a landscape of 6 identical but randomly spaced traps, and in Fig. 5b a landscape of 4 traps with random spacing, k and U0. Again the good fits and close correlation of theoretical and subsequently generated experimental potentials confirm that in principle once simple optical traps are fully characterized, any sort of optical landscape can be generated in a fully predictable manner. Experimental characterization in 2D, particularly of anisotropic traps, would however pose more of a challenge, because the particle can avoid steep increases in the potential.

Fig. 5 The particle velocity v(x) as a function of the position x when driven at a flow velocity of ∼ 5 μm s−1 through two different random optical landscapes: ○ experimental data, — is a fit according to Eq. (4). (a) six identical traps with random spacing. (b) four traps with random spacing, k and U0. The top panels in (a) and (b) show a comparison between the potentials, U(x), as obtained from the experiments (—) and predicted by Eq. (3) (□).

5. Conclusions

We have generated 1D optical potential energy landscapes using optical traps controlled by acousto-optical deflectors. Colloidal particles are driven through the optical landscapes by a well defined solvent flow. The full optical potential energy of both single optical traps and complex landscapes composed of multiple overlapping traps is determined by a simple force balance argument. Our flow based method is simple and straightforward to implement, allowing for fast and reliable characterizations of optical landscapes.

We find that the potential of a single optical trap is Gaussian, although noise in the experimental data may obscure previously reported stiffening of the optical trap. The magnitude of the trap stiffness and its linear dependence on laser power is found to be consistent with those found from thermal equilibrium methods. We also directly obtain the depth of the optical trap, which is shown to be linear with the laser power. Subsequently, various optical landscapes ranging from double-well potentials to random landscapes are generated from individually controlled optical traps. The corresponding energy landscapes as obtained from the velocity profiles are well described by a sum of single Gaussian optical traps. This in principle allows the fully controlled engineering of any sort of optical potential energy landscape, and we believe that our technique will be of interest for applications in micro-fluidic devices.

Acknowledgments

We thank the group of Clemens Bechinger (University of Stuttgart, Germany) for the design of the optical trapping setup. Thomas Skinner, Arran Curran and Samantha Ivell are thanked for useful discussions and critically reading the manuscript. This work was funded by the John Fell Fund and EPSRC.

References and links

1.

E. Gnecco, R. Bennewitz, T. Gyalog, Ch. Loppacher, M. Bammerlin, E. Meyer, and H.-J. Güntherodt, “Velocity Dependence of Atomic Friction,” Phys. Rev. Lett. 84, 1172–1175 (2000). [CrossRef] [PubMed]

2.

K. E. Kürten and C. Krattenthaler, “Multistability and multi 2π-kinks in the Frenkel-Kontorova model: an application to arrays of Josephson Junctions,” Int. J. Mod. Phys. B 21, 2324–2334 (2007). [CrossRef]

3.

V. K. Vlasko-Vlasov, A. E. Koshelev, U. Welp, W. Kwok, A. Rydh, G. W. Crabtree, and K. Kadowaki, “Magneto-optical imaging of Josephson vortices in layered superconductors,” in Magneto-Optical Imaging, T. H. Johansed and D. V. Shantsev, eds. (Springer, 2004), pp. 39–46. [CrossRef]

4.

B. Michel, A. Bernard, A. Bietsch, E. Delamarche, M. Geissler, D. Juncker, H. Kind, J.-P. Renault, H. Rothuizen, H. Schmid, P. Schmidt-Winkel, R. Stutz, and H. Wolf, “Printing meets lithography: Soft approaches to high-resolution patterning,” IBM J. Res. & Dev. 45, 697–719 (2001). [CrossRef]

5.

D. J. Harris, J. C. Conrad, and J. A. Lewis, “Evaporative lithographic patterning of binary colloidal films,” Phil. Trans. R. Soc. A 367, 5157–5165 (2009). [CrossRef] [PubMed]

6.

G. Zhang and D. Wang, “Colloidal Lithography - The Art of Nanochemical Patterning,” Chem. Asian J. 4, 236–245 (2009). [CrossRef]

7.

A. J. O’Reilly, C. Francis, and N. J. Quitoriano, “Gold nanoparticle deposition on Si by destabilising gold colloid with HF,” J. Colloid Interf. Sci. 370, 46–50 (2012). [CrossRef]

8.

A. Ashkin, “Acceleration and trapping of particles by radiation pressure,” Phys. Rev. Lett. 24, 156–159 (1970). [CrossRef]

9.

P. T. Korda, M. B. Taylor, and D. G. Grier, “Kinetically locked-in colloidal transport in an array of optical tweezers,” Phys. Rev. Lett. 89, 128301 (2002). [CrossRef] [PubMed]

10.

M. P. MacDonald, G. C. Spalding, and K. Dholakia, “Microfluidic sorting in an optical lattice,” Nature 426, 421–424 (2003). [CrossRef] [PubMed]

11.

G. Milne, D. Rhodes, M. MacDonald, and K. Dholakia, “Fractionation of polydisperse colloid with acousto-optical generated potential energy landscapes,” Opt. Lett. 32, 1144–1146 (2007). [CrossRef] [PubMed]

12.

K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E 82, 051407 (2010). [CrossRef]

13.

C. Bechinger, M. Brunner, and P. Leiderer, “Phase Behavior of Two-Dimensional Colloidal Systems in the Presence of Periodic Light Fields,” Phys. Rev. Lett. 86, 930–934 (2001). [CrossRef] [PubMed]

14.

D. Babic, C. Schmitt, I. Poberaj, and C. Bechinger, “Stochastic resonance in colloidal systems,” Europhys. Lett. 67, 158–164 (2004). [CrossRef]

15.

C. Schmitt, B. Dybiec, P. Hänggi, and C. Bechinger, “Stochastic resonance vs. resonant activation,” Europhys. Lett. 74, 937–943 (2006). [CrossRef]

16.

R. D. L. Hanes, C. Dalle-Ferier, M. Schmiedeberg, M. C. Jenkins, and S.U. Egelhaaf, “Colloids in one dimensional random energy landscapes,” Soft Matter 8, 2714–2723 (2012). [CrossRef]

17.

A. Curran, M. P. Lee, R. Di Leonardo, J. M. Cooper, and M. J. Padgett, “Partial synchronization of stochastic oscillators through hydrodynamic coupleing,” Phys. Rev. Lett. 108, 240601 (2012). [CrossRef] [PubMed]

18.

T. Bohlein, J. Mikhael, and C. Bechinger, “Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces,” Nat. Materials 11, 126–130 (2012). [CrossRef]

19.

T. Bohlein and C. Bechinger, “Experimental observation of directional locking and dynamical ordering of colloidal monolayers driven across quasiperiodic substrates,” Phys. Rev. Lett. 109, 058301 (2012). [CrossRef] [PubMed]

20.

K. C. Neuman and S. M. Block, “Optical trapping,” Rev. Sci. Instrum. 75, 2787 (2004). [CrossRef]

21.

J. Dobnikar, M. Brunner, H. H. von Grünberg, and C. Bechinger, “Three-body interactions in colloidal systems,” Phys. Rev. E 69, 031402 (2004). [CrossRef]

22.

A. C. Richardson, S. N. S. Reihani, and L. B. Oddershede, “Non-harmonic potential of a single beam optical trap,” Opt. Express 16, 15709–15717 (2008). [CrossRef] [PubMed]

23.

T. Godazgar, R. Shokri, and S. N. Reihani, “Potential mapping of optical tweezers,” Optics Letters 36, 3284–3286 (2011). [CrossRef] [PubMed]

24.

M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett. 36, 1260–1262 (2011). [CrossRef] [PubMed]

25.

R. R. Brau, J. M. Ferrer, H. Lee, C. E. Castro, B. K. Tam, P. B. Tarsa, P. Matsudaira, M. C. Boyce, R. D. Kamm, and M. J. Lang, “Passive and active microrheology with optical tweezers,” J. Opt. A: Pure Appl. Opt. 9, S103–S112 (2007). [CrossRef]

26.

M. Tassieri, G. M. Gibson, R. M. L. Evans, A. M. Yao, R. Warren, M. J. Padgett, and J. M. Cooper, “Measuring storage and loss moduli using optical tweezers: Broadband microrheology,” Phys. Rev. E 81, 026308 (2012). [CrossRef]

27.

A. V. Arzola, K. Volke-Sepulveda, and J. L. Mateos, “Force mapping of an extended light pattern in an inclined plane: Deterministic regime,” Opt. Express 17, 3429–3440 (2009). [CrossRef] [PubMed]

28.

K. Ladavac, K. Kasza, and D. G. Grier, “Sorting mesoscopic objects with periodic potential landscapes: Optical fractionation,” Phys. Rev. E 70, 010901 (2004). [CrossRef]

29.

M. J. Padgett and R. Di Leonardo, “Holographic optical tweezers and their relevance to lab on chip devices,” Lab Chip 11, 1196–1205 (2011). [CrossRef] [PubMed]

30.

J. Happel and H. Brenner, Low Reynolds Number Hydrodynamics (Kluwer Academic Publishers, Dordrecht, The Netherlands, 1983).

31.

A. V. Straube, A. A. Louis, J. Baumgartl, C. Bechinger, and R. P. A. Dullens, “Pattern formation in colloidal explosions,”Europhys. Lett. 94, 48008 (2011). [CrossRef]

32.

T. Tlusty, A. Meller, and R. Bar-Ziv, “Optical Gradient Forces of Strongly Localized Fields,” Phys. Rev. Lett. 81, 1738–1741 (1998). [CrossRef]

33.

J. Leach, H. Mushfique, S. Keen, R. Di Leonardo, G. Ruocco, J. M. Cooper, and M. J. Padgett, “Comparison of Faxns correction for a microsphere translating or rotating near a surface,” Phys. Rev. E 79, 026301 (2009). [CrossRef]

34.

Aresis d.o.o., Aresis beam steering controller and Tweez software (2007).

35.

J. C. Crocker and D. G. Grier, “Methods of Digital Video Microscopy for Colloidal Studies,” J. Colloid Interface Sci. 179, 298–310 (1996). [CrossRef]

36.

E. Weeks, Particle tracking using IDL, http://www.physics.emory.edu/weeks/idl/.

37.

A. Rohrbach, “Stiffness of Optical Traps: Quantitative Agreement between Experiment and Electromagnetic Theory,” Phys. Rev. Lett. 95, 168102 (2005). [CrossRef] [PubMed]

38.

Y. Harada and T. Asakura, “Radiation forces on a dielectric sphere in the Rayleigh scattering regime,” Opt. Commun. 124, 529–541 (1996). [CrossRef]

OCIS Codes
(110.0180) Imaging systems : Microscopy
(140.7010) Lasers and laser optics : Laser trapping
(350.4990) Other areas of optics : Particles
(350.4855) Other areas of optics : Optical tweezers or optical manipulation

ToC Category:
Optical Trapping and Manipulation

History
Original Manuscript: October 23, 2012
Revised Manuscript: November 23, 2012
Manuscript Accepted: November 26, 2012
Published: December 10, 2012

Virtual Issues
Vol. 8, Iss. 1 Virtual Journal for Biomedical Optics

Citation
Michael P. N. Juniper, Rut Besseling, Dirk G. A. L. Aarts, and Roel P. A. Dullens, "Acousto-optically generated potential energy landscapes: Potential mapping using colloids under flow," Opt. Express 20, 28707-28716 (2012)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-20-27-28707


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References

  1. E. Gnecco, R. Bennewitz, T. Gyalog, Ch. Loppacher, M. Bammerlin, E. Meyer, and H.-J. Güntherodt, “Velocity Dependence of Atomic Friction,” Phys. Rev. Lett.84, 1172–1175 (2000). [CrossRef] [PubMed]
  2. K. E. Kürten and C. Krattenthaler, “Multistability and multi 2π-kinks in the Frenkel-Kontorova model: an application to arrays of Josephson Junctions,” Int. J. Mod. Phys. B21, 2324–2334 (2007). [CrossRef]
  3. V. K. Vlasko-Vlasov, A. E. Koshelev, U. Welp, W. Kwok, A. Rydh, G. W. Crabtree, and K. Kadowaki, “Magneto-optical imaging of Josephson vortices in layered superconductors,” in Magneto-Optical Imaging, T. H. Johansed and D. V. Shantsev, eds. (Springer, 2004), pp. 39–46. [CrossRef]
  4. B. Michel, A. Bernard, A. Bietsch, E. Delamarche, M. Geissler, D. Juncker, H. Kind, J.-P. Renault, H. Rothuizen, H. Schmid, P. Schmidt-Winkel, R. Stutz, and H. Wolf, “Printing meets lithography: Soft approaches to high-resolution patterning,” IBM J. Res. & Dev.45, 697–719 (2001). [CrossRef]
  5. D. J. Harris, J. C. Conrad, and J. A. Lewis, “Evaporative lithographic patterning of binary colloidal films,” Phil. Trans. R. Soc. A367, 5157–5165 (2009). [CrossRef] [PubMed]
  6. G. Zhang and D. Wang, “Colloidal Lithography - The Art of Nanochemical Patterning,” Chem. Asian J.4, 236–245 (2009). [CrossRef]
  7. A. J. O’Reilly, C. Francis, and N. J. Quitoriano, “Gold nanoparticle deposition on Si by destabilising gold colloid with HF,” J. Colloid Interf. Sci.370, 46–50 (2012). [CrossRef]
  8. A. Ashkin, “Acceleration and trapping of particles by radiation pressure,” Phys. Rev. Lett.24, 156–159 (1970). [CrossRef]
  9. P. T. Korda, M. B. Taylor, and D. G. Grier, “Kinetically locked-in colloidal transport in an array of optical tweezers,” Phys. Rev. Lett.89, 128301 (2002). [CrossRef] [PubMed]
  10. M. P. MacDonald, G. C. Spalding, and K. Dholakia, “Microfluidic sorting in an optical lattice,” Nature426, 421–424 (2003). [CrossRef] [PubMed]
  11. G. Milne, D. Rhodes, M. MacDonald, and K. Dholakia, “Fractionation of polydisperse colloid with acousto-optical generated potential energy landscapes,” Opt. Lett.32, 1144–1146 (2007). [CrossRef] [PubMed]
  12. K. Xiao and D.G. Grier, “Sorting colloidal particles into multiple channels with optical forces: Prismatic optical fractionation,” Phys. Rev. E82, 051407 (2010). [CrossRef]
  13. C. Bechinger, M. Brunner, and P. Leiderer, “Phase Behavior of Two-Dimensional Colloidal Systems in the Presence of Periodic Light Fields,” Phys. Rev. Lett.86, 930–934 (2001). [CrossRef] [PubMed]
  14. D. Babic, C. Schmitt, I. Poberaj, and C. Bechinger, “Stochastic resonance in colloidal systems,” Europhys. Lett.67, 158–164 (2004). [CrossRef]
  15. C. Schmitt, B. Dybiec, P. Hänggi, and C. Bechinger, “Stochastic resonance vs. resonant activation,” Europhys. Lett.74, 937–943 (2006). [CrossRef]
  16. R. D. L. Hanes, C. Dalle-Ferier, M. Schmiedeberg, M. C. Jenkins, and S.U. Egelhaaf, “Colloids in one dimensional random energy landscapes,” Soft Matter8, 2714–2723 (2012). [CrossRef]
  17. A. Curran, M. P. Lee, R. Di Leonardo, J. M. Cooper, and M. J. Padgett, “Partial synchronization of stochastic oscillators through hydrodynamic coupleing,” Phys. Rev. Lett.108, 240601 (2012). [CrossRef] [PubMed]
  18. T. Bohlein, J. Mikhael, and C. Bechinger, “Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces,” Nat. Materials11, 126–130 (2012). [CrossRef]
  19. T. Bohlein and C. Bechinger, “Experimental observation of directional locking and dynamical ordering of colloidal monolayers driven across quasiperiodic substrates,” Phys. Rev. Lett.109, 058301 (2012). [CrossRef] [PubMed]
  20. K. C. Neuman and S. M. Block, “Optical trapping,” Rev. Sci. Instrum.75, 2787 (2004). [CrossRef]
  21. J. Dobnikar, M. Brunner, H. H. von Grünberg, and C. Bechinger, “Three-body interactions in colloidal systems,” Phys. Rev. E69, 031402 (2004). [CrossRef]
  22. A. C. Richardson, S. N. S. Reihani, and L. B. Oddershede, “Non-harmonic potential of a single beam optical trap,” Opt. Express16, 15709–15717 (2008). [CrossRef] [PubMed]
  23. T. Godazgar, R. Shokri, and S. N. Reihani, “Potential mapping of optical tweezers,” Optics Letters36, 3284–3286 (2011). [CrossRef] [PubMed]
  24. M. Jahnel, M. Behrndt, A. Jannasch, E. Schäffer, and S. W. Grill, “Measuring the complete force field of an optical trap,” Opt. Lett.36, 1260–1262 (2011). [CrossRef] [PubMed]
  25. R. R. Brau, J. M. Ferrer, H. Lee, C. E. Castro, B. K. Tam, P. B. Tarsa, P. Matsudaira, M. C. Boyce, R. D. Kamm, and M. J. Lang, “Passive and active microrheology with optical tweezers,” J. Opt. A: Pure Appl. Opt.9, S103–S112 (2007). [CrossRef]
  26. M. Tassieri, G. M. Gibson, R. M. L. Evans, A. M. Yao, R. Warren, M. J. Padgett, and J. M. Cooper, “Measuring storage and loss moduli using optical tweezers: Broadband microrheology,” Phys. Rev. E81, 026308 (2012). [CrossRef]
  27. A. V. Arzola, K. Volke-Sepulveda, and J. L. Mateos, “Force mapping of an extended light pattern in an inclined plane: Deterministic regime,” Opt. Express17, 3429–3440 (2009). [CrossRef] [PubMed]
  28. K. Ladavac, K. Kasza, and D. G. Grier, “Sorting mesoscopic objects with periodic potential landscapes: Optical fractionation,” Phys. Rev. E70, 010901 (2004). [CrossRef]
  29. M. J. Padgett and R. Di Leonardo, “Holographic optical tweezers and their relevance to lab on chip devices,” Lab Chip11, 1196–1205 (2011). [CrossRef] [PubMed]
  30. J. Happel and H. Brenner, Low Reynolds Number Hydrodynamics (Kluwer Academic Publishers, Dordrecht, The Netherlands, 1983).
  31. A. V. Straube, A. A. Louis, J. Baumgartl, C. Bechinger, and R. P. A. Dullens, “Pattern formation in colloidal explosions,”Europhys. Lett.94, 48008 (2011). [CrossRef]
  32. T. Tlusty, A. Meller, and R. Bar-Ziv, “Optical Gradient Forces of Strongly Localized Fields,” Phys. Rev. Lett.81, 1738–1741 (1998). [CrossRef]
  33. J. Leach, H. Mushfique, S. Keen, R. Di Leonardo, G. Ruocco, J. M. Cooper, and M. J. Padgett, “Comparison of Faxns correction for a microsphere translating or rotating near a surface,” Phys. Rev. E79, 026301 (2009). [CrossRef]
  34. Aresis d.o.o., Aresis beam steering controller and Tweez software (2007).
  35. J. C. Crocker and D. G. Grier, “Methods of Digital Video Microscopy for Colloidal Studies,” J. Colloid Interface Sci.179, 298–310 (1996). [CrossRef]
  36. E. Weeks, Particle tracking using IDL, http://www.physics.emory.edu/weeks/idl/ .
  37. A. Rohrbach, “Stiffness of Optical Traps: Quantitative Agreement between Experiment and Electromagnetic Theory,” Phys. Rev. Lett.95, 168102 (2005). [CrossRef] [PubMed]
  38. Y. Harada and T. Asakura, “Radiation forces on a dielectric sphere in the Rayleigh scattering regime,” Opt. Commun.124, 529–541 (1996). [CrossRef]

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