Renewable Solid Electrodes in Microfluidics: Recovering the Electrochemical Activity without Treating the Surface

Abstract

The contamination, passivation, or fouling of the detection electrodes is a serious problem undermining the analytical performance of electroanalytical devices. The methods to regenerate the electrochemical activity of the solid electrodes involve mechanical, physical, or chemical surface treatments that usually add operational time, complexity, chemicals, and further instrumental requirements to the analysis. In this paper, we describe for the first time a reproducible method for renewing solid electrodes whenever their morphology or composition are nonspecifically changed without any surface treatment. These renewable electrodes are the closest analogue to the mercury drop electrodes. Our approach was applied in microfluidics, where the downsides related to nonspecific modifications of the electrode are more critical. The renewal consisted in manually sliding metal-coated microwires across a channel with the sample. For this purpose, the chip was composed of a single piece of polydimethylsiloxane (PDMS) with three parallel channels interconnected to one perpendicular and top channel. The microwires were inserted in each one of the parallel channels acting as working, counter, and pseudoreference electrodes for voltammetry. This assembly allowed the renewal of all the three electrodes by simply pulling the microwires. The absence of any interfaces in the chips and the elastomeric nature of the PDMS allowed us to pull the microwires without the occurrence of leakages for the electrode channels even at harsh flow rates of up to 40.0 mL min. We expect this paper can assist the researchers to develop new microfluidic platforms that eliminate any steps of electrode cleaning, representing a powerful alternative for precise and robust analyses to real samples.

Low-Cost and Rapid-Production Microfluidic Electrochemical Double-Layer Capacitors for Fast and Sensitive Breast Cancer Diagnosis

“…With regard to the fabrication of the device, PSR is a simple, low-cost, solventless, and bondless approach that eliminates the use of cleanroom facilities. − Another advantage of this prototyping is its compatibility to incorporate 3D functional components and complex channels in a single piece of PDMS. − As an illustration, the fabrication of some 3D units using the PSR technique is shown in Figures S5–S7.…”

“…The fabrication of the chips was based on previous works reported by our group. − Microfluidic devices of a single piece of PDMS featured four to eight parallel channels that were produced through a bondless, low-cost, and cleanroom-free technique of sequential steps of polymerization and scaffold removal (PSR). Briefly, a scaffold of the channel is shaped and then PDMS is poured.…”

“…Herein we address a sensor that combines low-cost with both rapid fabrication and simple, fast, and sensitive determination of a breast cancer biomarker. Microfluidic chips containing electrochemical double-layer capillary capacitors (μEDLC) in polydimethylsiloxane (PDMS) substrate were obtained by a bondless and cleanroom-free prototyping that basically needs a laboratory oven and allows the fabrication of dozens to hundreds of chips in 1 h. − The electrodes consist of low-cost stainless-steel capillaries, whose large-scale production is well-established. These electrodes were reversibly introduced into the channels and utilized as received, without any surface chemical modification.…”

Design of Electrochemical Microfluidic Detectors: A Review

“…[108,109] In terms of the mechanical strength, PDMS can tolerate about 1 MPa pressure, resulting in a flow rate limitation. [6,102,110]…”

Converging Multidimensional Sensor and Machine Learning Toward High-Throughput and Biorecognition Element-Free Multidetermination of Extracellular Vesicle Biomarkers

“…Microfluidic devices composed of the PDMS elastomer were fabricated by a bondless, scalable, and cleanroom-free method that is based on sequential steps of polymerization and scaffold removal as highlighted in the Supporting Information. − The sample channel had a diameter of 700.0 μm. The HB cores were reversibly inserted above and below the sample channel as exhibited in Figure B, avoiding laborious routines to irreversibly attach electrodes to the device .…”