http://mdpi.com/journal/sensors/special_issues/polymer_ph_sensors/ The pH sensor has many uses in chemistry, biology, environmental monitoring, especially water quality control and so forth. Advances in semiconductor sensor technology, medical diagnostics and health care needs boosted a rapid research into novel miniaturised pH sensors, which can be used in vivo for continuous patient monitoring. The $180 million pH sensor market in the US and $400-500m globally is well established and fragmented, with over 45 companies serving laboratory and industrial applications. The need for developing truly biocompatible materials for sensor fabrication remains the most significant challenge for achieving robust and reliable sensors capable of monitoring the real-time physiological status of patients. In recent years, considerable interest has focused on development of chemical or biological sensors using functional polymers. By introduction of functional groups, polymers can be designed to selectively swell and shrink, thereby changing mass and elasticity, as a function of analyte concentration. Various polymers have also been considered suitable for potentiometric pH sensors. Full research papers are encouraged for submission, which present new experimental or theoretical results; new modification/combination of detection principles in a broad field of polymer-based pH sensors. It can feature all aspects of amperometric, potentiometric, conductometric, coulometric, impedimetric, voltammetric and so forth pH sensors for numerous applications. There are no length restrictions for the manuscripts. http://mdpi.com/1424-8220/8/1/561/ Stimuli-responsive hydrogels are materials with great potential for development of active functionalities in fluidics and micro-fluidics. Based on the current state of research on pH sensors, hydrogel sensors are described qualitatively and quantitatively for the first time. The review introduces the physical background of the special properties of stimuli-responsive hydrogels. Following, transducers are described which are able to convert the non-electrical changes of the physical properties of stimuli-responsive hydrogels into an electrical signal. Finally, the specific sensor properties, design rules and general conditions for sensor applications are discussed. http://mdpi.com/1424-8220/8/1/561/ Fri, 25 Jan 2008 00:00:00 CET Sensors 2008-01-25 8 1 Review 561 581 1424-8220 Review on Hydrogel-based pH Sensors and Microsensors 2008-01-25 doi: 10.3390/s8010561 Andreas Richter Georgi Paschew Stephan Klatt Jens Lienig Karl-Friedrich Arndt Hans-Jürgen P. Adler http://mdpi.com/1424-8220/7/12/3472/ Shake flasks are commonly used for process development in biotechnologyindustry. For this purpose a lot of information is required from the growth conditions duringthe fermentation experiments. Therefore, Anderlei et al. developed the RAMOS technology[1, 2], which proviedes on-line oxygen and carbondioxide transfer rates in shake flasks.Besides oxygen consumption, the pH in the medium also plays an important role for thesuccessful cultivation of micro-organisms and for process development. For online pHmeasurement fiber optical methods based on fluorophores are available. Here a combinationof the on-line Oxygen Transfer Rate (OTR) measurements in the RAMOS device with anon-line, fiber optical pH measurement is presented. To demonstrate the application of thecombined measurement techniques, Escherichia coli cultivations were performed and on-line pH measurements were compared with off-line samples. The combination of on-lineOTR and pH measurements gives a lot of information about the cultivation and, therefore, itis a powerful technique for monitoring shake flask experiments as well as for processdevelopment. http://mdpi.com/1424-8220/7/12/3472/ Thu, 20 Dec 2007 00:00:00 CET Sensors 2007-12-20 7 12 Article 3472 3480 1424-8220 Combination of On-line pH and Oxygen Transfer Rate Measurement in Shake Flasks by Fiber Optical Technique and Respiration Activity MOnitoring System (RAMOS) 2007-12-20 doi: 10.3390/s7123472 Marco Scheidle Johannes Klinger Jochen Büchs http://mdpi.com/1424-8220/7/12/3329/ This paper reports on the results from the investigation into the pH sensitivity ofnovel PANI/PVB/PS3 composite films. The conductimetric sensing mode was chosen as itis one of the most promising alternatives to the mainstream pH-sensing methods and it is theleast investigated due to the popularity of other approaches. The films were deposited usingboth screen-printing and a drop-coating method. It was found that the best response to pHwas obtained from the screen-printed thick films, which demonstrated a change inconductance by as much as three orders of magnitude over the pH range pH2-pH11. Thedevices exhibited a stable response over 96 hours of operation. Several films were immersedin buffer solutions of different pH values for 96 hours and these were then investigated usingXPS. The resulting N 1s spectra for the various films confirmed that the change inconductance was due to deprotonation of the PANI polymer backbone. SEM andProfilometry were also undertaken and showed that no considerable changes in themorphology of the films took place and that the films did not swell or contract due toexposure to test solutions. http://mdpi.com/1424-8220/7/12/3329/ Wed, 19 Dec 2007 00:00:00 CET Sensors 2007-12-19 7 12 Article 3329 3346 1424-8220 pH Sensitivity of Novel PANI/PVB/PS3 Composite Films 2007-12-19 doi: 10.3390/s7123329 Edric Gill Arousian Arshak Khalil Arshak Olga Korostynska http://mdpi.com/1424-8220/7/12/3027/ This paper reviews current state-of-the-art methods of measuring pH levels that are based on polymer materials. These include polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory approach for ion concentration monitoring. http://mdpi.com/1424-8220/7/12/3027/ Fri, 30 Nov 2007 00:00:00 CET Sensors 2007-11-30 7 12 Review 3027 3042 1424-8220 State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China 2007-11-30 doi: 10.3390/s7123027 Olga Korostynska Khalil Arshak Edric Gill Arousian Arshak