Fig.1 A sketch of the two-channel lab-on-a-chip device with a semipermeable membrane for studying osmotic flow in the sugar-rich upper channel.

Osmotically driven flows are believed to be responsible for the translocation of sugar in plants, a process that takes place in the phloem sieve element cells. These cells form a micro-fluidic network which spans the entire length of the plant measuring from 0.01 mm in diameter in small plants to 0.1 mm in diameter in large trees. The mechanism driving these flows is believed to be the osmotic pressures that build up relative to the neighboring water-filled tissue in re­spon­se to loading and unloading of sugar into and out of the phloem cells in different parts of the plant. 

Experimental and theoretical verification of the osmosis hypothesis for real plants is difficult, however, in this project we employ analysis of artificial lab-on-a-chip system in an attempt to verify it. The core of the system is shown in Fig. 1: a water/suger-filled microchannel on top of a water-filled channel separated by a semi-permeable membrane. The osmotic pressure difference will drive water from the bottom to the top channel, and thus create a flow in the sugar solution. The results will be compared to measurements on living plant performed by our collaborators at Harvard University. 

In this combined theoretical and experimental project you will work with several topics: 

- Various techniques for solving the Navier-Stokes equation with osmosis included

- Numerical simulation using MatLab and COMSOL

- Fabrication by micromilling of polymer-based lab-on-a-chip system

- Measurements on the fabricated lab-on-a-chip system

- Comparison of theory and experiment