- Jonathan DeRocher
- Doctoral Candidate, Chemical Engineering
- Thesis: Layer-by-Layer Assembly in Confined Geometries
- co-advised by Michael F. Rubner, Dept. of Materials Science & Engineering
- M.S. Chemical Engineering Practice, MIT, 2008
- C.P.G.S. Chemical Engineering, University of Cambridge, 2006
- B.S. Chemical Engineering, University of Minnesota, 2005
- Email: jpderoch@mit.edu
- Phone: (617) 253-6478
- Office: 66-357
Research Summary
Microfluidic and nanofluidic devices hold great potential as a platform for manipulation and analysis of small sample volumes. The high throughput and high surface area possible with these devices suggests applications in biomolecule or chemical detection, selective separation, and heterogeneous catalysis. To realize some of this potential, the surfaces of these devices can be modified to impart functionality to the device. Polyelectrolyte multilayers (PEMs) can be used to impart a broad array of novel functionalities to a surface including stimuli-responsiveness, reversible switching of the gap thickness, manipulation of the sign and/or the density of the surface charge, chemical functionality and wettability of a surface.
Our paper entitled "Layer-by-Layer Assembly of Polyelectrolytes in Nanofluidic Devices" (Macromolecules 43, 2430-2437) describes our use of a hybrid micro/nanofluidic device which contains an array of parallel nanochannels to study PEM deposition in confined geometries. Layer-by-layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) was used to conformally coat the nanochannel walls, systematically narrowing the channel width from 240 nm to 30 nm. The thicknesses of confined multilayers were measured using SEM and these results were compared with those obtained on planar, unconfined surfaces. A procedure for direct measurement of the gap thickness using DC conductance was also developed. LbL assembly in the nanochannels resulted in slightly lower bilayer thicknesses than those obtained on planar surfaces. This observation can be attributed to the depletion of unadsorbed polyelectrolytes within the channel after charge reversal of the coated channel walls occurs.
