The efficient transport of particles through narrow channels is essential to the functioning of a diverse range of systems, from the biological, where pores control translocation across cell membranes, to the industrial, where porous materials play key roles in filtration, batteries and sensing technologies. Especially complex is the case of polymer translocation, where the chain-like structure of the macromolecule leads to a complex interplay of effects, and as such this process remains poorly understood.
In this project the student will investigate the transport of colloidal model polymers in microfluidic channels. These polymers will be formed from superparamagnetic colloidal spheres that upon the application of an external magnetic field form chains2, previously used as primitive models for polymers2. These experiments will build upon extensive work considering the dynamics of single particles in microfluidic channels3,4, with direct comparison to these results allowing for the impact of directional interparticle interactions upon translocation dynamics to be fully elucidated. By sensitively tuning the system parameters, the effect on translocation of the complex interplay between chain length, channel dimensions, chain stiffness and external driving force can also be studied. Results from this novel model system will be compared to theoretical models for polymer transport, allowing for truly quantitative tests of these models. This will provide unprecedented insight into the fundamental principles governing transport of macromolecules, relevant to the future design of molecular sensors, batteries and selective membranes
Deterministic aggregation kinetics of superparamagnetic colloidal particles P. Reynolds, K. E. Klop, F. A. Lavergne, S. M. Morrow, D. G. A. L. Aarts, R. P. A. Dullens, J. Chem. Phys. 143, 214903 (2015)
Fluctuation dynamics of a single magnetic chain R. Silva, R. Bond, F. Plouraboue and D. Wirtz, Phys. Rev. E, 54, 5502, (1996)
Anisotropic diffusion of spherical particles in closely confining microchannels S. L. Dettmer, S. Pagliara, K. Misiunas, U. F. Keyser, Phys. Rev. E. 89, 062305 (2014)
Nondecaying Hydrodynamic Interactions along Narrow Channels K. Misiunas, S. Pagliara, E. Lauga, J. R. Lister, U. F. Keyser, Phys. Rev. Lett. 115, 038301 (2015)
There has probably never existed a material that has been assigned as many superlatives, and garnered as much hype as graphene. By exploiting the 'strongest' and 'thinnest' material, this project aims to eventually achieve high resolution sensing across the single atomic plane of graphene analysing DNA structures and digital barcodes . The experimental setup features a novel method of contacting the graphene membrane; glass capillaries are brought into contact with the membrane [a] until a seal is established [b]. This graphene tipped capillary is then exposed to a variety of electrolytes or materials allowing for electrical characterisation and ionic data collection.
Defects within the membrane have shown selective porosity toward cations [2,3]. Currently, work is being
made to tune this selectivity toward anions. Studying the effect of the type of salt and solvent used towards
this effort is of particular interest. Understanding these extrinsic effects would enhance the single molecule
sensing in this novel system.
In addition, methods are currently being used to create 3-10nm diameter pores within the membrane via
dielectric breakdown . These larger pores are used to sense the translocation of DNA across the
membrane [c]. This very exciting research comes with challenges in choices of solvent, consideration of
DNA-graphene interactions and electrical noise.
Mustafa, Jeff, Ulrich
 Bell, Nicholas AW, and Ulrich F. Keyser. "Digitally encoded DNA nanostructures for multiplexed, single-molecule protein sensing with nanopores." (2016)
 Walker, Michael I., et al. "Measuring the proton selectivity of graphene membranes." Applied Physics Letters 107.21 (2015): 213104
 Walker, Michael I., et al. "Extrinsic Cation Selectivity of 2D Membranes." ACS nano 11.2 (2017): 1340-1346
 Kuan, Aaron T., et al. "Electrical pulse fabrication of graphene nanopores in electrolyte solution." Applied physics letters 106.20 (2015): 203109