Self-cleaning and mixing microfluidic elements
Apparatus and methods are disclosed for mixing and self-cleaning elements in microfluidic systems based on electrothermally induced fluid flow. The apparatus and methods provide for the control of fluid flow in and between components in a microfluidic system to cause the removal of unwanted liquids and particulates or mixing of liquids. The geometry and position of electrodes is adjusted to generate a temperature gradient in the liquid, thereby causing a non-uniform distribution of dielectric properties within the liquid. The dielectric non-uniformity produces a body force and flow in the solution, which is controlled by element and electrode geometries, electrode placement, and the frequency and waveform of the applied voltage.
1. A mixing element for a microdevice comprising:
a) a mixing compartment having a principal axis of symmetry in fluid communication with a channel and
b) first through fourth pairs of electrically coupled, elongated mixing electrodes located on the interior surface of the mixing compartment wherein:
(i) the first electrodes of the first and second mixing electrode pairs are adjacent and parallel to one another and aligned axially with respect to the principal axis of symmetry;
(ii) the second electrodes of the first and second mixing electrode pairs are adjacent and parallel to one another and aligned with a plane orthogonal to the principal axis of symmetry;
(iii) the first electrodes of the third and fourth mixing electrode pairs are adjacent and parallel to one another and aligned axially with respect to the principal axis of symmetry; and
(iv) the second electrodes of the third and fourth mixing electrode pairs are adjacent and parallel to one another and aligned with a plane orthogonal to the principal axis of symmetry.
2. The mixing element of claim 1 , wherein the mixing compartment has a square or rectangular cross sectional geometry.
3. The mixing element of claim 1 wherein the principal axis of symmetry is orthogonal to the channel.