Development of microfluidic LED sensor platform

Abstract

We developed the microfluidic light emitting diode (LED) sensor for methanol detection. The linear gradient-generating microfluidic device consists of two inlet and four outlet microchannels. The concentration gradients of methanol were stably generated in the microfluidic platform in a temporal and spatial manner. The methanol harvested from microfluidic platforms was analyzed by measuring electrical conductivity, showing that currents were decreased with the methanol content. The methanol in the microfluidic device was also observed by LED sensor. Therefore, this microfluidic LED device could be a powerful platform for methanol sensor applications.Keywords: LED sensor; Microfluidic gradient device; Methanol detection; Electrical conductivity BackgroundMethanol, the simplest alcohol and organic solvent, has widely been used for fuel cell and biochemical applications [1][2][3]. The direct methanol fuel cell is of great benefit for portable electronic devices, because it enables increase of power density and decrease of operating temperature [4][5][6]. The physical and chemical properties of methanol are also similar to gasoline, showing that methanol is a good candidate as a fuel cell in automotive engines [7][8][9]. Despite many methanol-based industrial applications, the major problem is still remained, such as methanol toxicity, which can cause severe disease of metabolic acidosis, nerve disorder, olfactory mucosa, and blindness [10]. Although small amount of methanol is inhaled, methanol becomes toxic formic acid via formaldehyde as previously described [11]. In general, the volatile organic compound (e.g., methanol), which can be conventionally detected by gas chromatography technique, has low boiling point and high reactive property. Thus, the development of the platform technology to detect the methanol at room temperature has become imperative [12].Microfluidic devices have previously been developed to generate concentration gradients and detect biomolecules [13][14][15]. Recently, an integrated microfluidic device has been developed to quantify methanol concentrations [16]. The methanol and methanol oxidase infused into the poly (methyl methacrylate) (PMMA)-based microfluidic device. The injected solutions were heated at 45°C to generate formaldehyde and methanol concentrations were subsequently observed by ultraviolet (UV) spectrophotometer. The accuracy of microfluidic device-based methanol detection was approximately 93% compared to gas chromatography method. Integrated microfluidic device has been developed to detect methanol concentrations [17]. The system consisted of light emitting diode (LED) photometer, PMMA-based microfluidic device, photodiode, voltmeter, and temperature controller. The samples were loaded and were subsequently mixed by a vortex stirrer in the microfluidic device. The colorimetric reaction of the mixtures was performed by thermoelectric cooler and micro-hotplate systems. LED photometer system detected methanol concentrations in the microfluidic device. Furthermore, mi...

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