Development of wearable electronic devices, on low-cost flexible support for gas sensing applications

Identifier:  TDX:4576

Handle: https://hdl.handle.net/20.500.11797/TDX4576

Authors:  Santos Betancourt, Alejandro

Abstract:
This thesis combines low-dimensional materials for gas sensing with electronic devices to collect environmental data such as pollution and air quality. The thesis reaches the knowledge base of designing and developing wearable devices on low-cost flexible support to monitor humans' exposure to target gases. The first part gives historical statistical data on pollutant gases and their relationship with human well-being. It presents an overview of gas sensors and the main characteristics next-generation electronics for gas sensing applications should have such as IoT and ANNs. Second, AACVD was used to synthesize WO3-based sensors on alumina substrates with platinum-IDEs. Sensors´ responses were evaluated towards oxidizing and reducing gases such as NO2, EtOH, and H2. Measured data was collected as a sensor array and was processed using a multivariate approach. Then, PCA and MPL were employed to obtain high discrimination and quantization ability. Third, to interface this type of chemoresistor gas sensors a technology readiness level (TRL-4) platform was designed and set up. The platform consists of several nodes (electronics boards) connected to a centralized server using the MQTT IoT protocol. A methodology is presented to set up the platform when deployed in different scenarios or interfacing with other sensors. To develop this methodology two pollutant gases were measured, NO2 and NH3, in a single form (under % RH variation) and under their mixture. Full details about the design of hardware, software, and ANNs training process are given. The final section of the thesis presents the fabrication of graphene-based sensors incorporating interdigitated electrodes in the same flexible printed circuit board as the electronics. Graphene-based sensors were obtained using the airbrushing deposition technique. A cumulative NFC wearable for NO2 sensing applications was fabricated. The obtained wearable device can be easily attached to a working vest allowing simple integration in any working environment.