Banca de DEFESA: Layse Mendes Diniz

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Layse Mendes Diniz
DATE: 14/03/2024
TIME: 14:00
LOCAL: Microsoft TEAMS
TITLE:

Application of Hemicellulose as a Flexible Substrate in Pressure, Temperature, and Humidity Sensors.

KEY WORDS:

flexible conductive substrate, hemicellulose, films, natural polymers.

PAGES: 105
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUBÁREA: Engenharia Térmica
SPECIALTY: Aproveitamento da Energia
SUMMARY:

  Technological advancement has been driving the need for sensors in various applications, which raises environmental concerns related to the use of non-biodegradable and potentially toxic materials. In response, the scientific community has been dedicated to the development of flexible and conductive devices, using materials from renewable sources. In this scenario, biopolymers, especially hemicellulose extracted from plant fibers, stand out due to their natural abundance and renewability, good thermal stability, biodegradability, and biocompatibility. However, as hemicellulose is not a natural conductor, the addition of conductive fillers becomes essential. This research focuses on the use of hemicellulose as a base for flexible sensors, aiming to develop hemicellulose conductive films with metallic nanoparticles and pure hemicellulose substrates with printed circuits, to evaluate their effectiveness as sensors. Hemicellulose was extracted from jute fibers using 10% w/v KOH, followed by the production of pure hemicellulose polymer films and films with silver nanoparticles (AgNPs) at different concentrations, employing the water casting technique. The films were analyzed using a variety of techniques, including Thermogravimetry (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) Spectroscopy, Scanning Electron Microscopy (SEM), Dynamic Mechanical Analysis (DMA), and tensile mechanical tests. Roughness was assessed through optical microscopies and Gwyddion 2.55 software, while surface tension was determined by contact angle measurements. Electrical properties were tested with a bench multimeter, and tests for pressure, temperature, and humidity variation were conducted. The results showed that the hemicellulose films possess good thermal stability, low porosity, low roughness, and hydrophilic properties. The inclusion of silver nanoparticles not only improved the electrical conductivity but also the thermal stability of the material. The performance of the nanocomposites as sensors for pressure, temperature, and humidity varies according to the concentration of incorporated nanoparticles. For the pressure sensor, under high pressures, the nanocomposite containing 5% silver nanoparticles (AgNP) showed the best results, also proving to be effective in temperature detection. In situations of lower pressures, the nanocomposite with a concentration of 0.50% AgNP had the most satisfactory response. As for humidity measurement, the nanocomposites with 1% and 5% AgNP showed superior performances. Moreover, hemicellulose proved to be an effective substrate for the printing of conductive inks, especially for pressure and temperature sensors. These findings confirm the potential of hemicellulose as a promising material for the development of multifunctional flexible sensors, contributing both to scientific and technological advancement and to global efforts in search of more sustainable and eco-friendly solutions.

COMMITTEE MEMBERS:
Externa à Instituição - ALBANIZA ALVES TAVARES - UFCG
Interno - 3138349 - EDGAR AMARAL SILVEIRA
Externa ao Programa - 1721557 - MARIA DEL PILAR HIDALGO FALLA - nullExterno à Instituição - MICHEL BRIENZO - UNESP
Presidente - 1720225 - SANDRA MARIA DA LUZ