Category Archives: Research

Core-shell particles

Identifying and tracking individual particles within a dense sample can be a challenge, especially in 3D.  One approach for circumventing this has been to fluorescently label only the core or center of each particle, providing a clear separation between the observable particle centers.  However, the colloidal chemistry required to achieve this has not been trivial.  Using an innovative technique, we can produce bulk quantities of micrometer-sized fluorescently-labelled core-shell particles, without the need for complex organic chemistry.

References:

  • R.P.A. Dullens, Soft Matter 2, 805 (2006)
  • M.T. Elsesser, A.D. Hollingsworth, K.V. Edmond, and D.J. Pine, Langmuir 27, 917 (2010)

Colloidal synthesis

Well defined colloidal model systems are of upmost importance in the study of colloidal dispersions. Using colloid chemistry the chemical and physical properties of the colloidal model system can be precisely adjusted to the physical experiments in mind. Therefore, the synthesis and characterization of colloidal model systems plays a central role in our research. A wide variety of chemical techniques is available to synthesize many different colloidal particles with very specific properties. For example, very monodisperse silica or latex spheres can be made, bit also rods, magnetic and fluorescent colloids can be prepared. Also the specific interactions between colloids can be controlled using surface chemistry. To characterize the particles several techniques such as light scattering, optical (confocal) microscopy and electron microscopy will be used.
Further reading:

Grain boundaries

The strength of materials is closely related to the grain size of the material. However, grain boundary stability is still far from understood. Using geometrical frustration, crystals which are rich in grain boundaries can be prepared. By studying the structural and dynamical behaviour of both colloidal single crystals and crystal imperfections insight will be gained into the relation between frustration and the stability of grain boundaries.

Further reading:

Microfluidics

The field of microfluidics can be defined as the study of the behaviour and manipulation of fluids geometrically confined in artificial microsystems, with typical lengthscales ranging from 1 μm to 1 mm. The devices are fabricated from polydimethylsiloxane (PDMS) using soft lithographic techniques in our clean room.

Part of our research focuses on using microfluidic devices with microsyringe pumps to create highly monodisperse Pickering emulsions. We also use microfluidic devices to study the confinement effects on colloids, such as the fd virus.

Further Reading:

  • Dammone, O. J., Zacharoudiou, I., Dullens, R. P. a., Yeomans, J. M., Lettinga, M. P., & Aarts, D. G. a. L. (2012). Confinement Induced Splay-to-Bend Transition of Colloidal Rods. Physical Review Letters, 109(10), 108303. doi:10.1103/PhysRevLett.109.108303
  • Bartolo, D., & Aarts, D. G. a. L. (2012). Microfluidics and soft matter: small is useful. Soft Matter,8(41), 10530. doi:10.1039/c2sm26157j
  • ​Stone, H. a., a.D. Stroock, & Ajdari, a. (2004). Engineering Flows in Small Devices. Annual Review of Fluid Mechanics, 36(1), 381–411. doi:10.1146/annurev.fluid.36.050802.122124
  • Anna, S., Bontoux, N., & Stone, H. (2003). Formation of dispersions using “flow focusing” inmicrochannels. Applied Physics Letters, 82(3), 364. doi:10.1063/1.1537519
  • Mcdonald, J., Duffy, D., Anderson, J., & Chiu, D. (2000). Fabrication of microfluidic systems in poly(dimethylsiloxane). Electrophoresis, 21, 27–40.