This article reports on a fiber‐based ratiometric optical pH sensor for use in real‐time and continuous in vivo pH monitoring in human tissue. Stable hybrid sol–gel‐based pH sensing material is deposited on a highly flexible plastic optical fiber tip and integrated with excitation and detection electronics. The sensor is extensively tested in a laboratory environment before it is applied in vivo in a human model. The pH sensor performance in the laboratory environment outperforms the state‐of‐the‐art reported in the current literature. It exhibits the highest sensitivity in the physiological pH range, resolution of 0.0013 pH units, excellent sensor to sensor reproducibility, long‐term stability, short response time of <2 min, and drift of 0.003 pH units per 22 h. The sensor also exhibits promising performance in in vitro whole blood samples. In addition, human evaluations conducted under this project demonstrate successful short‐term deployment of this sensor in vivo.

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Organic and printed electronics integration has the potential to revolutionise many technologies, including biomedical diagnostics. This work demonstrates the successful integration of multiple printed electronic functionalities into a single device capable of the measurement of hydrogen peroxide, and total cholesterol. The single-use device employed printed electrochemical sensors for hydrogen peroxide electroreduction integrated with printed electrochromic display and battery. The system was driven by a conventional electronic circuit designed to illustrate the complete integration of silicon ICs via pick and place, or using organic electronic circuits. The device was capable of measuring 8 µL samples of both hydrogen peroxide (0 to 5 mM, 2.72×10 -6 A.mM -1 ) and total cholesterol in serum from 0 to 9 mM (1.34×10 -8 A.mM -1 , r 2 =0.99, RSD <10%, n=3) which was output on a semi-quantitative linear bar display. The device could operate for 10 minutes via a printed battery and display the result for many hours or days. A mobile phone 'app' was also capable of reading the test result and transmitting this to a remote health care provider. Such a technology could allow improved management of conditions such as hypercholesterolemia.Printed electronics is being hailed as a technological revolution, equal in importance to the emergence of microelectronics over 50 years ago. The combined qualities of print-processable organic, inorganic and hybrid (semi)conductive materials which can be deposited onto flexible polymeric substrates using a range of additive, high throughput printing methodologies offer the prospect of low cost mass production capability and the potential for unprecedented levels of technological integration.

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