title: Nano-enabled paper humidity sensor for mobile based point-of-care lung function monitoring.
abstract: The frequency of breathing and peak flow rate of exhaled air are necessary parameters to detect chronic obstructive pulmonary diseases (COPDs) such as asthma, bronchitis, or pneumonia. We developed a lung function monitoring point-of-care-testing device (LFM-POCT) consisting of mouthpiece, paper-based humidity sensor, micro-heater, and real-time monitoring unit. Fabrication of a mouthpiece of optimal length ensured that the exhaled air was focused on the humidity-sensor. The resistive relative humidity sensor was developed using a filter paper coated with nanoparticles, which could easily follow the frequency and peak flow rate of the human breathing. Adsorption followed by condensation of the water molecules of the humid air on the paper-sensor during the forced exhalation reduced the electrical resistance of the sensor, which was converted to an electrical signal for sensing. A micro-heater composed of a copper-coil embedded in a polymer matrix helped in maintaining an optimal temperature on the sensor surface. Thus, water condensed on the sensor surface only during forcible breathing and the sensor recovered rapidly after the exhalation was complete by rapid desorption of water molecules from the sensor surface. Two types of real-time monitoring units were integrated into the device based on light emitting diodes (LEDs) and smart phones. The LED based unit displayed the diseased, critical, and fit conditions of the lungs by flashing LEDs of different colors. In comparison, for the mobile based monitoring unit, an application was developed employing an open source software, which established a wireless connectivity with the LFM-POCT device to perform the tests.
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam 781039, India. Electronic address: mitradip@iitg.ernet.in.
authors.forename: Mitradip
authors.initials: M
authors.lastname: Bhattacharjee
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam 781039, India; Department of Electronics and Electrical Engineering, Indian Institute of Technology Guwahati, Assam 781039, India. Electronic address: harshal@iitg.ernet.in.
authors.forename: Harshal B
authors.initials: HB
authors.lastname: Nemade
authors.affiliation: Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam 781039, India; Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam 781039, India. Electronic address: dipban@iitg.ernet.in.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Bandyopadhyay
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D045853:Exhalation; D006801:Humans; D006813:Humidity; D008168:Lung / Q000737:chemistry* / Q000503:physiopathology; D008991:Monitoring, Physiologic / Q000379:methods*; D019095:Point-of-Care Systems; D012815:Signal Processing, Computer-Assisted; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water
keywords: Humidity; Lung-function; Nanoparticle; Point-of-care testing; Sensor