Q4 A start-up company is launching a microfluidic device based on a compact disc (CD) platform. Individual chambers are radially distributed on the disc. One of these elements is depicted in Figure Q4 below. The sample is placed in the inlet chamber and, during rotation the liquid, it is moved into the metering chamber. Between the metering chamber and the collection reservoir, there is a valve based on a hydrophobic patch. The channel dimensions are 80 um wide and 25 um tall. inlet chamber metering chamber with defined volume overflow channel 80 m valve: barrier with hydrophobic patch 25pm: Cross-section of the channel ventilation waste collection reservoir (for subsequent steps) Figure Q4. Sketch illustrating part of the microfluidic channels on a CD based diagnostic platform. (a) = 5 cm from the centre of the disc is the metering chamber which holds a small quantity of water. There is a hydrophobic patch forming a barrier that has a water contact angle of 110. Knowing that the capillary force is Fe = mycos DH and the centrifugal force is Fu = prw?, determine the required rotational rate, w, in RPM for the disc to break the hydrophobic barrier. y and p are the surface tension and density of water, respectively. Dy is the hydrodynamic diameter of the channel. [6]