Pattern deposition in a microfluidic chamber

Mohammad Abo Jabal, Chemical Engineering, Technion, Hifa, Israel
Ofer Manor, Chemical Engineering, Technion, Hifa, Israel


Controlled self-assembly of deposits – pattern deposition – from volatile solutions or suspensions, is a process that enables the organization of soft and hard materials of interest including polymers, nanoparticles, and biomaterials into complex structures of high regularity. Nowadays, pattern deposition is being used by many companies in order to avoid expensive fabrication procedures; the most common of which is photolithography. The recent interest of the industry in pattern deposition has led to an abundance of studies on the physics and applications of the deposition process. The most common experimental procedure employed is the placing of a sessile droplet of a volatile solution or suspension on a solid surface. Nevertheless, this technique has limited ability to yield a reproducible, regular, and well defined patterns required for a thorough investigation of the physical mechanisms occurring during the deposition process. Examples for such mechanisms are colloidal forces in the form of the van der Waals and the electrical double layer forces, external stimuli such as acoustic and electric fields, etc.

We employ a simple model system, allowing for a well-defined experimental procedure in terms of geometry and ambient conditions. Our experimental system comprising a rectangular microfluidics chamber in which we inject a polymeric solution (PMMA in Toluene). During evaporation, the Toluene solution de-wets the solid surface of the chamber. The three-phase contact line between the solid substrate of the cell and the solution moves in a "stick-slip" motion while being aligned as a straight line due to the geometry of the cell. The deposition occurs when the contact line sticks to the substrate, producing periodic strips with width, thickness, and periodicity down to 1 µm, 20 nm, and 2 µm, respectively. In this presentation,