Optical non-contact localization of liquid-gas interfaces on disk during rotation for measuring flow rates and viscosities

Abstract

We present a novel technique for the spatio-temporally resolved localization of liquid-gas interfaces on centrifugal microfluidic platforms based on total internal reflection (TIR) at the channel wall. The simple setup consists of a line laser and a linear image sensor array mounted in a stationary instrument. Apart from identifying the presence of usually unwanted gas bubbles, the here described online meniscus detection allows to measure liquid volumes with a high precision of 1.9%. Additionally, flow rates and viscosities (range: 1-12 mPa s, precision of 4.3%) can be sensed even during rotation at frequencies up to 30 Hz.

Volumetric measurements by image segmentation on centrifugal microfluidic platforms in motion

“…Stopping a CM platform may result in unintended capillary induced flow in channels that could cause both a loss of sample and a disruption of the intended operation of the platform. 7 While application-specific volume measurements on microfluidic platforms have been successfully accomplished through methods such as the use of impedance measurements on an electrowetting on dielectric (EWOD) platform, 14 total internal reflection of a laser beam on a single channel in a CM platform, 15 or microscopy images of water-in-oil droplets, 16 there is currently a lack of a robust, multipurpose volume measurement technique for CM platforms in motion. This lack can be remedied through dimensional measurements obtained from the segmentation of real time platform images, which are often acquired to conduct a visual, qualitative evaluation of a CM platform's performance.…”

Anti-Counterfeit Technologies for Microfluidic “Lab-on-a-Disc” Systems

“…Ideally, the detection scheme should align with the flow control, manufacturing and low-complexity instrumentation paradigm of the LoaD platform. As an example, optical absorption [88] or total internal reflection (TIR) [89,90] based on the refractive index can be transduced by rather simple, instrument-based transduction concepts.…”

Employing fluorescence analysis for real-time determination of the volume displacement of a pneumatically driven diaphragm micropump

“…Opticalbased measurement techniques mainly track the advancing of a fluid meniscus or a fluidic interface in a channel [31][32][33][34][37][38][39][40]. In [44] Hoffmann et al present an optical technique to spatio-temporally resolve liquid-gas interfaces for flow rate measurement in a microchannel. However, a meniscus is not always visible in a microfluidic process or the channel section is too short for the recording of a whole pumping cycle.…”