Recent Developments in Ozone Sensor Technology for Medical Applications

Abstract

There is increasing interest in the utilisation of medical gases, such as ozone, for the treatment of herniated disks, peripheral artery diseases, and chronic wounds, and for dentistry. Currently, the in situ measurement of the dissolved ozone concentration during the medical procedures in human bodily liquids and tissues is not possible. Further research is necessary to enable the integration of ozone sensors in medical and bioanalytical devices. In the present review, we report selected recent developments in ozone sensor technology (2016-2020). The sensors are subdivided into ozone gas sensors and dissolved ozone sensors. The focus thereby lies upon amperometric and impedimetric as well as optical measurement methods. The progress made in various areas-such as measurement temperature, measurement range, response time, and recovery time-is presented. As inkjet-printing is a new promising technology for embedding sensors in medical and bioanalytical devices, the present review includes a brief overview of the current approaches of inkjet-printed ozone sensors.

Keywords: dissolved ozone; electrochemical sensors; inkjet-printing; medical applications; optical sensors; ozone gas; ozone sensors.

Figure 1

Schematic of possible applications for ozone treatment in healthcare. The applications reach from disk herniation and osteoarthritis, to coronary and peripheral artery disease, madelung disease, dyslipidemia, cholesterol embolism, and dentistry.

Figure 2

Number of publications featuring ozone sensors. Source: Scopus. Data extracted on 12 March 2020. All documents containing ozone and sensor were considered in the query and these documents were subdivided into the respective years.

Figure 3

Schematic of a basic sensor structure, which consists of a membrane, sensing material, substrate, and encapsulation. The materials are employed in regard to integrate the sensor in medical and bioanalytical devices.

Figure 4

Schematic of an amperometric sensor. Between the working and reference electrode, a constant voltage is applied. The current, measured at the working electrode, changes when ozone is present in the measurement substance.

Figure 5

Schematic of an impedimetric sensor. (a) The bottom, side, and top views of the impedimetric sensor. (b) An expanded view of the sensor. Resistance Ω of the sensing material changes when ozone is present in the measurement substance.

Figure 6

Schematic of an optical absorption sensor. The measurement method is based on measuring the light absorption of the measurement substance that is sent out by emitting diodes and detected by a photosensor.

Figure 7

Schematic of typical fabrication methods for ozone sensors. The substrate is shown in blue and the applied ink or thin film material in red. (a) The spin-coating process. (b) A schematic of dip-coating/immersion. (c) The screen-printing process. (d) The UV photolithography process. (e) The spray-coating/spray pyrolysis process. (f) The inkjet-printing process.