Development of a medical fiber-optic pH sensor based on optical absorption

Wolthuis, Roger A.; McCrae, David A.; Saaski, E. W.; Hartl, James C.; Mitchell, Gordon L.

doi:10.1109/10.135548

Cited by 56 publications

(20 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…pH 10 measurements were performed in continuous flow mode using fiber-optic light guides aligned to the device using an in-house made cell. The main advantage of these sensors is that no reagent indicator is needed to measure the pH, because the PAni acts as the indicator itself, reducing the complexity of pH detection 15 inside microchannels. The functionalisation process is easy and highly reproducible from microdevice to microdevice and over the whole microchannel length.…”

Section: Discussionmentioning

confidence: 99%

“…Microfluidic device fabrication 15 The fabrication of the master mold was carried out using a laser ablation system-excimer/CO 2 laser (Optec Laser Micromachining Systems, Belgium) by cutting the microfluidic structures in a 50 µm double-sided pressure sensitive adhesive film, PSA, (AR8890, Adhesives Research, Ireland) and pasting 20 one of the PSA sides to a petri dish 47 .…”

Section: Methodsmentioning

confidence: 99%

“…It is important to note that the absorbance spectrum changes very rapidly after the solution reaches the detection area (approx. 2 s), thereby ensuring a very fast response 15 of the device (see ESI † -videos 1 and 2). Moreover, the signal remains stable during the timescale of the experiment, which was set to 5 minutes.…”

Section: Ph Measurementsmentioning

confidence: 99%

“…Digital image capture 15 After the fabrication of the flow channels and subsequent analysis using reference instrumentation (spectrophotometer) the channels were then subjected to analysis via digital imaging techniques. The channel was placed within the field of view of a standard colour camera (Panasonic DMC-FZ38) along with a white 20 background for subsequent image processing.…”

Section: Measurement Of Absorbance Spectra Of Pani Coatingsmentioning

confidence: 99%

“…30 In particular, optical pH sensors present several advantages over the traditional pH electrodes as such their low costs, immunity from electromagnetic field, absence of electric contacts, possibility of reference electrode removal and a high degree of miniaturisation 14 . Optical fiber-based pH sensors have been 35 particularly popular, as the fibre allows the optical signal to be transported over long distances, which can facilitate applications in remote sensing 15 .…”

mentioning

confidence: 99%

See 4 more Smart Citations

Dynamic pH mapping in microfluidic devices by integrating adaptive coatings based on polyaniline with colorimetric imaging techniques

et al. 2013

View full text Add to dashboard Cite

In this paper we present a microfluidic device that has integrated pH optical sensing capabilities based on polyaniline. The optical properties of polyaniline coatings change in response to the pH of the solution that is flushed inside the microchannel offering the possibility of monitoring pH in continuous flow over a wide pH range throughout the entire channel length. This work also features an innovative detection 10 system for spatial localisation of chemical pH gradients along microfluidic channels through the use of a low cost optical device. Specifically, the use of a microfluidic channel coated with polyaniline is shown to respond colorimetrically to pH and that effect is detected by the detection system, even when pH gradients are induced within the channel. This study explores the capability of detecting this gradient by means of imaging techniques and the mapping of the camera's response to its corresponding pH after a 15 successful calibration process. The provision of an inherently responsive channel means that changes in the pH of a sample moving through the system can be detected dynamically using digital imaging along the entire channel length in real time, without the need to add reagents to the sample. This approach is generic and can be applied to other chemically responsive coatings immobilised on microchannels. Introduction 20Conventional glass-type electrodes have been widely used for pH measures for many years in both industry and academic areas. However, in terms of specific applications (e.g. in vivo, food industry, or for clinical applications), they posses several disadvantages due to their size constraints, rigidity, and the 25 inflexibility of the glass electrode. In recent years, a wide number of pH sensors have been developed to overcome these limitations, including ion sensitive field-effect transistor (iSFET) pH sensors 1-4 , optical pH sensors based on pH responsive dyes 5-8 , hydrogel film pH sensors 9, 10 , and solid-state metal oxides pH sensors 11-13 . 30 In particular, optical pH sensors present several advantages over the traditional pH electrodes as such their low costs, immunity from electromagnetic field, absence of electric contacts, possibility of reference electrode removal and a high degree of miniaturisation 14 . Optical fiber-based pH sensors have been 35 particularly popular, as the fibre allows the optical signal to be transported over long distances, which can facilitate applications in remote sensing 15 .Usually, these optical pH sensors (or optrodes) employ a dye or an indicator that requires immobilisation onto a solid support 40 material. There are several critical issues related to this approach: firstly, the dye should retain its optical properties after the immobilisation process 16 and secondly, it should not leach into the solution 17. A third issue of practical importance is their inherently narrow dynamic response range which is usually 45 around 3-4 pH-units centred on the dye´s pKa 18 .Therefore, the further improvement of such sensors focuses...

show abstract

Section: Discussionmentioning

confidence: 99%