confined soft matter; electrostatics; colloidal information; single molecule trap
Ruggeri Francesca, Krishnan Madhavi (2018), Entropic trapping of a singly charged molecule in solution, in NanoLetters
Ruggeri Francesca, Krishnan Madhavi (2018), Spectrally resolved single-molecule electrometry, in Journal of Chemical Physics
, 148, 123307.
Krishnan Madhavi (2017), A simple model for electrical charge in globular macromolecules and linear polyelectrolytes in solution, in Journal of Chemical Physics
Ruggeri Francesca, Krishnan Madhavi (2017), Lattice diffusion of a single molecule in solution, in Physical Review E
, 96, 062406.
Kokot Gasper, Bespalova Maria, Krishnan Madhavi (2017), Measured electrical charge of SiO2 in polar and nonpolar media, in Journal of Chemical Physics
Ruggeri Francesca, Zosel Franziska, Mutter Natalie, Różycka Mirosława , Wojtas Magdalena, Ożyhar Andrzej, Schuler Benjamin , Krishnan Madhavi (2017), Single-molecule electrometry, in Nature Nanotechnology
The aspiration to study Nature’s building blocks in isolation can be traced back over 200 years to the diaries of the first german Professor of Experimental Physics, Georg Christoph Lichtenberg, where he envisioned future experiments “suspending the constituents of matter free”. In the last 100 years Lichtenberg’s dream has turned into reality opening up a number of new research fields. In particular the last few decades have witnessed unprecedented advances from quantum optics to biophysics that were a direct consequence of newly acquired abilities to spatially trap and manipulate single entities in free space or solution. Examples include the development of ion traps, and the manipulation of colloidal objects in strongly focused light beams that led to the Bose-Einstein Condensation experiment; both areas were recognized with Nobel Prizes in Physics in 1989 and 1997 respectively.Trapping a single atom or molecule offers us the unique opportunity to study the individual components of matter, above and beyond the average properties of an ensemble, and free of strong interactions with immobilizing surfaces. While the external field-based approach has had revolutionary impact, these methods fail in a vital physical regime namely for small objects at room temperature. Thus while it has been possible for decades now to trap and experiment with cold ions and atoms, a whole class of Nature’s building blocks, i.e., biological macromolecules in aqueous solution had evaded similar control. In 2010 we reported the development of the electrostatic fluidic trap that addressed the long-standing problem of trapping in the regime of warm, small entities in solution. Starting June 2012, in the first three years of the SNF professorship at the University of Zurich, we have achieved the ability to trap single nanometer-scale macromolecules in room temperature solution and measure their properties such as electrical charge with single elementary charge resolution. On a separate front, we have also demonstrated the ability to store, write and readout information in the spatial state of a single, levitating colloidal particle, introducing a new concept in nanomechanical information.In the upcoming phase we wish to:  further advance our molecule trapping, detection and measurement abilities, widening the scope to cover single molecule structural biology studies at the fundamental level, and sensitive detection of minute molecular differences from an applied ‘molecular sensing’ perspective,  develop the area of “colloidal information” e.g., build single colloid-based logic circuits and possibly demonstrate rudimentary computation, as well as  at the fundamental level, pursue the problem of confinement-induced attraction between like-charged entities that has eluded explanation to date.