2.5. Microfluidic Device Development

A microfluidic device is developed following the Slip Chip approach [34]. The device is composed of three cast acrylic layers (McMaster-Carr product; Elmhurst, IL, USA), each having a thickness of 3.175 mm. The area of the device is 5 cm by 2.5 cm. The inlet and outlet ports are cut through the top layer and are 1.5 mm in diameter. The center layer has a microfluidic channel 40 mm in length, 1.5 mm in width and 3.175 mm in height. The bottom layer has an engraved microfluidic channel that matches that of the middle layer and is 40 mm in length, 1.5 mm in width and approximately 1 mm in depth. The three acrylic layers are placed on top of each other and held together by a press clamp. A white piece of paper is placed below the three acrylic layers in order to aid visualize colorimetric assay changes. The acrylic device was made using an EPILOG Mini CO₂ 60 W laser cutter. Each layer is made individually from cast acrylic. The inlet and outlet ports in the top layer and the microfluidic channel in the middle layer are made by cutting all the way through their respective acrylic layers using the following settings (speed: 25%, power: 75%, frequency: 2500 Hz). The bottom layer has an engraved channel made by using the following settings (speed: 80%, power: 30%, frequency: 2500 Hz).