Colour-Specific Microfluidic Droplet Detection for Molecular Communication

Abstract

Droplet-based microfluidic systems are a promising platform for lab-on-a-chip (LoC) applications. These systems can also be used to enhance LoC applications with integrated droplet control information or for data transmission scenarios in the context of molecular communication. For both use-cases the detection and characterisation of droplets in small microfluidic channels is crucial. So far, only complex lab setups with restricted capabilities have been presented as detection devices. We present a new low-cost and portable droplet detector. The device is used to confidently distinguish between individual droplets in a droplet-based microfluidic system. Using on-off keying a 16-bit sequence is successfully transmitted for the first time with such a setup. Furthermore, the devices capabilities to characterise droplets regarding colour and size are demonstrated. Such an application of a spectral sensor in a microfluidic system presents new possibilities, such as colour-coded data transmission or analysis of droplet content. CCS CONCEPTS• Hardware → Sensor devices and platforms.

Advanced Characterisation of a Sensor System for Droplet-Based Microfluidics

“…where t drop denotes the observed droplet duration at the sensor, ∆d = 6.35 mm the fixed distance between the two sensors and ∆t the delay between detection of the same droplets rising edge at the two sensors. We demonstrated the basic principle for droplet size detection in [5]. Now, to mitigate a linear offset between the calculated droplet size using the developed sensor and the result of a camera-based video processing software used as reference, we extend (1) with correction factors m and c:…”

“…Using the spectral sensor the colour of microfluidic droplets can be determined. Again, a proof of concept with six different colours was made in [5]. We now present a detailed analysis of the sensor specificity and inspect a sample transmission scenario with an alphabet of 126 colours.…”

“…Droplet-based microfluidic setups provide a promising platform for various lab-on-chip (LoC) applications, such as drug screening or capillary electrophoresis [1], [2]. In some cases it is desirable to encode and transmit information using droplets or measure droplet parameters in such a setup [3]- [5]. Dropletbased communication was presented as a theoretical principle in [6], a demonstration of first practical applications was performed in [7].…”

“…A promising low-cost optical sensor device with a compact design, suitable for detection of various droplet parameters, such as size and colour in a microfluidic setup, was proposed in [5]. The aim of this work is to further investigate the capabilities of this sensor device for droplet characterisation in terms of droplet size and colour, which can be used for information encoding in data transmission scenarios, as well as for other LoC applications.…”

“…Data is recorded with a microprocessor and can be retrieved over a serial connection. The attached cables connect to the separate LED light sources[5].…”