Micro-optofluidic switch realized by 3D printing technology

This paper presents a PDMS micro-optofluidicchip that allows a laser beam to be driven directly towarda two-phase flow stream in a micro-channel while at thesame time automatically, detecting the slug’s passage andstirring the laser light, without the use of any external opticaldevices. When the laser beam interacts with the microfluidicflow, depending on the fluid in the channel and thelaser angle of incidence, a different signal level is detected.So a continuous air–water segmented flow will generate asignal that switches between two values. The device consistsof a T-junction, which generates the two-phase flow,and three optical fiber insertions, which drive the inputlaser beam toward a selected area of the micro-channel anddetects the flow stream. Three micro-channel sections ofdifferent widths were considered: 130, 250, 420 μm andthe performance of the models was obtained by comparingray-tracing simulations. The master of the device hasbeen realized by 3D printing technology and a protocolwhich realizes the PDMS chip is presented. The static anddynamic characterizations, considering both single flowsand two-phase flows, were carried out, and in spite of thedevice’s design simplicity, the sensitivity of the system tocapture changes in the segmented flows and to stir the laserlight in different directions was fully confirmed. The experimentaltests show the possibility of obtaining satisfactoryresults with channel diameters in the order of 200 μm.