Microfluidic Mixer with Automated Electrode Switching for Sensing Applications

Abstract

An electronic tongue (e-tongue) is a multisensory system usually applied to complex liquid media that uses computational/statistical tools to group information generated by sensing units into recognition patterns, which allow the identification/distinction of samples. Different types of e-tongues have been previously reported, including microfluidic devices. In this context, the integration of passive mixers inside microchannels is of great interest for the study of suppression/enhancement of sensorial/chemical effects in the pharmaceutical, food, and beverage industries. In this study, we present developments using a stereolithography technique to fabricate microfluidic devices using 3D-printed molds for elastomers exploring the staggered herringbone passive mixer geometry. The fabricated devices (microchannels plus mixer) are then integrated into an e-tongue system composed of four sensing units assembled on a single printed circuit board (PCB). Gold-plated electrodes are designed as an integral part of the PCB electronic circuitry for a highly automated platform by enabling faster analysis and increasing the potential for future use in commercial applications. Following previous work, the e-tongue sensing units are built functionalizing gold electrodes with layer-by-layer (LbL) films. Our results show that the system is capable of (i) covering basic tastes below the human gustative perception and (ii) distinguishing different suppression effects coming from the mixture of both strong and weak electrolytes. This setup allows for triplicate measurements in 12 electrodes, which represents four complete sensing units, by automatically switching all electrodes without any physical interaction with the sensor. The result is a fast and reliable data acquisition system, which comprises a suitable solution for monitoring, sequential measurements, and database formation, being less susceptible to human errors.

Microfluidic Point-of-Care Devices: New Trends and Future Prospects for eHealth Diagnostics

“…Another approach for microfluidic PoC devices includes microfluidic electronic tongues (e-tongues), i.e., an electronic device mimicking the biological recognition of human tongue papillae for comparison of tastes. Such devices are made as arrays of sensing units whose multisensory units can be used to establish "fingerprints" from complex liquid samples [69], i.e., the recognition patterns in these devices can be used for identification/distinction of samples [70]. In contrast with the high specificity of other approaches, where pure or ultrapure samples are required, this concept could be more efficient for simultaneous multisensory devices.…”

“…Such an integration makes this approach promising for future eHealth systems with computer-aided diagnosis, where machine learning, big data, and IoT technologies should converge with biosensing capabilities. In particular, biosensing applications are being explored with e-tongues by functionalizing the building nanolayers with biomolecules to control the specificity in the interactions with the analyte under study [68][69][70][71][72][73][74][75][76]. This latter application can be used to collect huge amounts of patient's biological data to feed machine learning algorithms, and then continuously convert them into knowledge (through big data and machine learning methods).…”

3D Printing Technologies in Biosensors Production: Recent Developments

“…The utilization of the CMOS image sensor embedded in a smartphone as an analytical detector for the analysis, given its cheapness and widespread global presence, highlighted the concept of the accessibility and portability of this biosensor. Braunger et al [9] used stereolithography (SLA) to fabricate 3D-printed microfluidic devices to be used as sensors for the recognition of human taste; for this reason, the device was reported by the authors as being an electronic tongue (e-tongue). An e-tongue is a multisensory device that is able to collect data from complex liquid media, elaborating this information with computational and statistical models that lead to the association of unknown samples with specific classes, enabling their identification and distinction.…”

“…Naturally occurring or in vitro expressed molecules such enzymes, cells, aptamers, deoxyribonucleic acid Thus, each AM technology presents its own peculiar characteristics in terms of printing time, printing materials, resolution, precision, object dimensions, reduced cost, and use in various applications. Among the different application fields, the world of sensors has seen the importance of 3D printing techniques blossom thanks to the essential advantages of rapid manufacturing above described [3,8,9]. The International Union of Pure and Applied Chemistry (IUPAC) provided the definition of a biosensor as a system that exploits selective biochemical interactions between analytes and specific enzymes, immunosystems, organelles, or whole cells for quantitative purposes, resulting in electrical, thermal, magnetic, or optical signals [10].…”

Leakage-Free Nucleic Acid Biochip Featuring Bioinert Photocurable Inhibitor

“…Their primary disadvantage is that most of these devices are prone to leakage, particularly at high pressures [30][31][32][33]. Even though the DNA fluid can quickly be introduced into a microchannel by injection, it can leak from the matrix through small gaps at the PDMS-PCB interface [34][35][36].…”