An amperometric nitric oxide sensor with fast response and ppb-level concentration detection relevant to asthma monitoringby Hithesh K. Gatty, Simon Leijonmarck, Mikael Antelius, Göran Stemme, Niclas Roxhed

Sensors and Actuators B: Chemical


Patterned Electrode-Based Amperometric Gas Sensor for Direct Nitric Oxide Detection within Microfluidic Devices

Wansik Cha, Yi-Chung Tung, Mark E. Meyerhoff, Shuichi Takayama

Fractional exhaled nitric oxide of at least 100 ppb and implications for future asthma research

Bradley E. Chipps, Christine T. Anderson, Julia M. Harder

Asthma, Viruses, and Nitric Oxide


Carbon Electrodes Modified by Nanoscopic Iron(III) Oxides to Assemble Chemical Sensors for the Hydrogen Peroxide Amperometric Detection

Jan Hrbac, Vladimir Halouzka, Radek Zboril, Kyriakos Papadopoulos, Theodor Triantis


Sensors and Actuators B 209 (2015) 639–644

Contents lists available at ScienceDirect

Sensors and Actuators B: Chemical jo ur nal home page: www.elsev ier .com/ locate /snb

An amp re concen oni


Göran St a Micro and Na b Applied Electr a r t i c l

Article history:

Received 4 Au

Received in re

Accepted 4 No

Available onlin


Nitric oxide




Gas sensor ide ( sthm urfac o det 0.045 sor i e (CO apabi s the © 2014 Elsevier B.V. All rights reserved. 1. Introduction

Asthma the airways patients, th used as a bi typically in surement s bench top s trochemica response ti needs to bu temporarily pumped at measureme to buffer an instrument itoring devi needs to be sor that elim ∗ Correspon

Stockholm, Sw

E-mail add faster sensor could be realized by fabricating a miniaturized sensor http://dx.doi.o 0925-4005/© is a disease characterized by chronic inflammation in of the lungs. For monitoring inflammation in asthma e concentration of nitric oxide (NO) in exhaled breath is omarker [1–6]. In adults, a concentration above 50 ppb dicates the presence of an inflammation [7–9]. A meaystem for asthma monitoring is described in [10]. This ystem contains a three-electrode amperometric elecl NO sensor with a size of a few cm3. Due to the long me of the sensor, of the order of 50 s, the instrument ffer the exhaled breath sample. The breath sample is first stored in a reservoir within the instrument and then a lower flow rate to the gas sensor for the concentration nt. The inclusion of gas sampling and handling systems d pump the sample, results in a large overall size of the (24 cm × 13 cm × 10 cm). To develop a hand-held monce that patients can carry along, the size of the system reduced. This could be achieved by having a faster seninates the need for buffering of the breath sample. A ding author at: Micro and Nanosystems, Osquldas väg 10, SE-100 44 eden. Tel.: +46 87909143. ress: (N. Roxhed). where diffusion lengths of the gas are inherently shorter.

In terms of state of the art of miniaturized and potentially fast

NO sensors; chemoresistive metal oxide sensors such as SnO2 have been used extensively in the past. However, their detection limit is in the range of few ppm, which is not sufficient for monitoring of asthma [11]. Miniaturized electrochemical sensors, such as amperometric sensors with a solid polymer electrolyte (SPE) have been shown to detect NO [12–14]. However, also for this type of sensors the limit of detection is not sufficient for application of these sensors in asthma monitoring.

Previously, we have demonstrated a miniaturized electrochemical NO sensor with a detection limit and sensitivity that is potentially suitable for asthma monitoring [15]. In this paper, we characterize its sensitivity to changes in relative humidity, response time, flow sensitivity and stability. In addition, the sensor is characterized for its sensitivity to carbon monoxide (CO) and ammonia (NH3), both common gases in exhaled breath [16,17] which potentially could interfere with electrochemical sensors.

Typical concentrations of CO and NH3 in exhaled breath are in the range of 0–8 ppm and 0–1 ppm, respectively. 2. Sensor design

The sensor design is based on the principle of amperometric detection of an NO analyte as illustrated in Fig. 1. The working, rg/10.1016/j.snb.2014.11.147 2014 Elsevier B.V. All rights reserved.erometric nitric oxide sensor with fast tration detection relevant to asthma m

K. Gattya, Simon Leijonmarckb, Mikael Anteliusa, emmea, Niclas Roxheda,∗ nosystems, KTH Royal Institute of Technology, Sweden ochemistry, KTH Royal Institute of Technology, Sweden e i n f o gust 2014 vised form 31 October 2014 vember 2014 e 15 December 2014 a b s t r a c t

A MEMS-based amperometric nitric ox to detect NO gas for the purpose of a combination of a microporous high-s liquid electrolyte. The sensor is able t and has a measured NO sensitivity of humidity. The settling time of the sen ammonia (NH3) and carbon monoxid the sensor. The ppb-level detection c high selectivity to CO and NH3 make detection.sponse and ppb-level toring

NO) gas sensor is reported in this paper. The sensor is designed a monitoring. The unique property of this sensor lies in the e area electrode that is coated with NafionTM, together with a ect gas concentrations of the order of parts-per-billion (ppb) nA/ppb and an operating range between 25 and 65% relative s measured to 8 s. The selectivity to interfering gases such as ) was high when placing an activated carbon fiber filter above lity of this sensor combined with its relatively fast response, sensor potentially applicable in gas monitoring for asthma 640 H.K. Gatty et al. / Sensors and Actuators B 209 (2015) 639–644

Fig. 1. Concep the nanoporou reference an stitute the consists of a are arrange face area. T layer and a trolyte with the pores fo of the gas s used as wor size is not s

The interac electrical b working ele the counter potentiosta the referenc directly pro 3. Experim

The fabr below. This with a work with the co electrolyte set-up and selectivity m added. 3.1. Fabrica

To fabric 9260, AZ El thick, 100 m a hot plate with energy graphically in Fig. 2. Th deep reacti through hol

D illustration of the working electrode die. The illustration shows the grid where the micropores are etched through the silicon wafer resulting in a face area. The inset picture shows a SEM image of the microporous grid. in Fig ng in mic t a 1 lay elec ectro ing th de w 1 cm

Nafi pre chip ents

TM la app

Nafio the c s of f thetual drawing of the three electrode electrochemical sensor showing s structure of the NafionTM layer covering the working electrode. d counter electrodes together with the electrolyte conbasic elements of the sensor. The working electrode microporous grid structure etched in silicon. The pores d in a close packed structure to achieve a high surhese pores are coated with a platinum (Pt) electrode layer of NafionTM, which acts as a solid polymer eleca nanoporous structure. The utilization of the walls of r the working electrode facilitates the miniaturization ensor. The Platinum–NafionTM combination has been king electrode before, however its non-integrated large uitable for the hand-held application in mind [18–20]. tion between the gas, electrode, and electrolyte under ias leads to the oxidation of NO at the surface of the ctrode causing a current flow between the working and electrode. The output current is then measured using a t maintaining a constant voltage of +0.7 V compared to e electrode. The resulting current through the sensor is portional to the NO gas concentration. ental