1558-1748 (c) 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2019.2952940, IEEE Sensors Journal > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—A paper based chemiresistor has been fabricated to selectively sense ethanol in human breath. The chemiresistor was composed of a sensing mixture of multiwall-carbon-nano-tubes (MWCNTs), poly (diallyl-dimethyl-ammonium chloride) (PDDA), alcohol dehydrogenase (ADH), and coenzyme (NADH). The aluminum electrode was deposited on the paper surface, followed by drop-casting of the aforementioned sensing mixture. The resistance of the sensors was measured by exposing the same in gas-vapor mixture as well as the sample solution. The surface- modified MWCNTs specifically broke down ethanol present in the gas-vapor mixture or in a solution to generate a quantitative electronic response proportional to the ethanol concentration. Subsequently, the interference of other volatile organic materials was also tested to prove the selectivity and sensitivity of the sensor towards ethanol in the presence of different volatile organic compounds (VOCs). The variation of the resistance during the interaction between sensor and ethanol was also characterized by measuring the surface potential of the channel material under ethanol exposure using Kelvin probe force microscopy (KPFM). The sensor was integrated with a voltage divider circuit, a display, and a microcontroller unit to make a proof-of-concept prototype for the point-of-care (POC) detection of ethanol in human breath. Index Terms—Chemiresistor, Ethanol Sensor, MWCNTs, Paper. I. INTRODUCTION XPOSURE to volatile organic compounds (VOCs) either as indoor or outdoor pollutants cause various ailments ranging from eye, nose, lung, liver, kidney to the central nervous systems [1]. The major sources of VOCs in the air are paints and their solvents, wood additives, aerosol sprays, cleansers and disinfectants, repellents, fuels, and automotive products [2-4]. Since most of the VOCs have a negative impact on the environment and subsequently on human health, point- of-care (POC) detection of them is perhaps the need of the hour [5]. For example, portable, inexpensive, and user-friendly VOC detection devices are already in use in the industries like food and beverage, paint, biomedical, pharmaceutical, and oil, This paragraph of the first footnote will contain the date on which you submitted your paper for review. “We thank MeitY grant no. 5(9)/2012-NANO, Government of India, for financial aids.” Corresponding authors: Tapas K. Mandal, Harshal B. Nemade, and Dipankar Bandyopadhyay. Nirmal Roy, Nayan Mani Das and Nilanjan Mandal are with the Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam - 781039 India (e-mail: nirmalroy.ece@gmail.com, nayanmanidas3@gmail.com, nilanjan.mandal@gmail.com). Shirsendu Mitra is with the Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam - 781039 India (e-mail: shirsenduofficial@gmail.com). among others [6, 7]. Apart from industrial gaseous or volatile effluents, VOCs are also present in human breath depending on abnormal metabolism or intoxications [8, 9]. Thus, of late, the POC detection of toxic VOCs in human breath has also become important to measure the quality of human health. Intake of alcoholic beverages can increase the concentration of ethanol in the exhaled air, which is an intoxicated state of health condition. In particular, driving under the influence (DUI) of alcohol has been deemed illegal beyond a permissible breath alcohol concentration (BrAC) of 0.05% - 0.08% owing to its fatal accidental consequences across the world [10]. Further, due to its flammable properties, sensing and detection of ethanol vapor are also essential during the large scale production of ethanol and fuel processing [11]. In this direction, of late, sensitive, and specific POC detection of ethanol from a gas-mixture is on high demand owing to its applicability in arresting DUI or fire hazards. A low-cost, portable, and user-friendly device with fast response time is expected to detect ethanol specifically from human breath or air in the presence of other VOCs or gases. The major challenge in the development of such sensors has been the significantly low concentrations of ethanol in human breath or air [12]. Traditionally, there are a number of centralized and costly analytical techniques such as gas chromatography (GC), spectrophotometry and high performance liquid chromatography (HPLC) have been available for such measurements in an accurate as well as specific manner [13, 14]. Of late, employing the principle of micro or nanosciences, a wide range of electrochemical, resistive, gravimetric, or optical sensors have been developed for the detection of VOCs [15-17]. In particular, for alcohol sensing, various inorganic materials have been employed in the sensor architecture, such as Au-doped ZnO nanowires, CdIn2O4, CdO-Fe2O3, TiO2, V2O5, and Indium oxide nanowire [18-20]. A few attempts have also been made to design electrodes from carbon-based [21] or organic [10] materials, which are used as working electrodes for electrochemical Harshal B Nemade is with the Department of Electronics and Electrical Engineering and Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam - 781039 India (e-mail: harshal@iitg.ac.in). Tapas K Mandal and Dipankar Bandyopadhyay are with the Department of Chemical Engineering and Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam - 781039 India (e-mail: tapasche@iitg.ac.in, dipban@iitg.ac.in). Nirmal Roy, Shirsendu Mitra, Nayan Mani Das, Nilanjan Mandal, Dipankar Bandyopadhyay, Harshal B. Nemade, Member, IEEE, and Tapas K. Mandal Paper Based Enzymatic Chemiresistor for POC Detection of Ethanol in Human breath E