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Sensors 2014, 14(7), 11629-11639; doi:10.3390/s140711629
Article

Parylene C-Based Flexible Electronics for pH Monitoring Applications

1,* , 1
,
2
,
1
 and
1,3
1 Centre for Bio-Inspired Technology, Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2AZ, UK 2 National Heart and Lung Institute, Imperial College London, London W12 0NN, UK 3 Nano Research Group, Department of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK
* Author to whom correspondence should be addressed.
Received: 22 May 2014 / Revised: 21 June 2014 / Accepted: 27 June 2014 / Published: 1 July 2014
(This article belongs to the Special Issue Implantable Sensors)
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Abstract

Emerging materials in the field of implantable sensors should meet the needs for biocompatibility; transparency; flexibility and integrability. In this work; we present an integrated approach for implementing flexible bio-sensors based on thin Parylene C films that serve both as flexible support substrates and as active H+ sensing membranes within the same platform. Using standard micro-fabrication techniques; a miniaturized 40-electrode array was implemented on a 5 μm-thick Parylene C film. A thin capping film (1 μm) of Parylene on top of the array was plasma oxidized and served as the pH sensing membrane. The sensor was evaluated with the use of extended gate discrete MOSFETs to separate the chemistry from the electronics and prolong the lifetime of the sensor. The chemical sensing array spatially maps the local pH levels; providing a reliable and rapid-response (<5 s) system with a sensitivity of 23 mV/pH. Moreover; it preserves excellent encapsulation integrity and low chemical drifts (0.26–0.38 mV/min). The proposed approach is able to deliver hybrid flexible sensing platforms that will facilitate concurrent electrical and chemical recordings; with application in real-time physiological recordings of organs and tissues.
Keywords: Parylene C; flexible electronics; pH sensor; extended gate; discrete MOSFETs Parylene C; flexible electronics; pH sensor; extended gate; discrete MOSFETs
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Trantidou, T.; Tariq, M.; Terracciano, C.M.; Toumazou, C.; Prodromakis, T. Parylene C-Based Flexible Electronics for pH Monitoring Applications. Sensors 2014, 14, 11629-11639.

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