EcoSensHeal: Self-sensing and self-healing composites for high responsibility applications based on recycled materials

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Plasma Actuators Based on Alumina Ceramics for Active Flow Control Applications

Publication . Rodrigues, Frederico; Shvydyuk, Kateryna; Nunes-Pereira, João; Pascoa, Jose; Silva, Abilio

Plasma actuators have demonstrated great potential for active flow control applications, including boundary layer control, flow separation delay, turbulence control, and aircraft noise reduction. In particular, the material used as a dielectric barrier is crucial for the proper operation of the device. Currently, the variety of dielectrics reported in the literature is still quite restricted to polymers including Kapton, Teflon, poly(methyl methacrylate) (PMMA), Cirlex, polyisobutylene (PIB) rubber, or polystyrene. Nevertheless, several studies have highlighted the fragilities of polymeric dielectric layers when actuators operate at significantly high-voltage and -frequency levels or for long periods. In the current study, we propose the use of alumina-based ceramic composites as alternative materials for plasma actuator dielectric layers. The alumina composite samples were fabricated and characterized in terms of microstructure, electrical parameters, and plasma-induced flow velocity and compared with a conventional Kapton-based actuator. It was concluded that alumina-based dielectrics are suitable materials for plasma actuator applications, being able to generate plasma-induced flow velocities of approximately 4.5 m/s. In addition, it was verified that alumina-based ceramic actuators can provide similar fluid mechanical efficiencies to Kapton actuators. Furthermore, the ceramic dielectrics present additional characteristics, such as high-temperature resistance, which are not encompassed by conventional Kapton actuators, which makes them suitable for high-temperature applications such as turbine blade film cooling enhancement and plasma-assisted combustion. The high porosity of the ceramic results in lower plasma-induced flow velocity and lower fluid mechanical efficiency, but by minimizing the porosity, the fluid mechanical efficiency is increased.

2024Journal article

Open access

Manufacturing and characterisation of a piezoresistive strain sensor based on the rGO@PDMS composite for skin and prosthetic support systems

Publication . Gonçalves Ferreira, Rodrigo; Pereira Silva, A; Nunes-Pereira, João

Due to an ever-increasing amount of population focusing more on their personal health, thanks to rising living standards, there is a pressing need to improve personal healthcare devices. These devices presently require laborious, time-consuming, and convoluted procedures that heavily rely on cumbersome equipment, causing discomfort and pain for the patients during invasive methods such as sample-gathering, blood sampling, and other traditional bench-top techniques [1]. The solution lies in the development of new flexible sensors with temperature, humidity, strain, pressure, and sweat detection and monitoring capabilities, mimicking some of the sensory capabilities of the skin [2]. Along these lines, carbon-based composite materials, which include graphene and other allotropes, have also garnered significant interest due to their electromechanical stability, extraordinary electrical conductivity, high specific surface area, variety, and relatively low cost [3].Thus, in this work, a piezoresistive strain sensor based on a polydimethylsiloxane (PDMS) composite nano reinforced with reduced graphene oxide (rGO) was manufactured, characterised, and tested for possible applications which include joint movement and breathing pattern monitoring, exhibiting the physical and electromechanical characteristics required for the effective detection of physiological signals. The samples were prepared via solution casting, followed by characterisation of the piezoresistive effect of the material, mechanical (3-point bending and tensile), morphological (SEM), structural (FTIR), and thermal (TGA) properties, along with performance testing in live-human’s body parts. Regarding results, it was observed the influence of the used PDMS elastomer-crosslinker ratio, cure temperature and time, dispersant and rGO content in the final performance of the sensor, with the possibility to tune certain characteristics to be better adjusted to specific applications. For this kind of application, the indicated elastomer-crosslinker is 15:1 cured at 120 °C for 20 minutes, with isopropyl alcohol as the dispersant and a rGO content between 3-5 wt.%. The obtained average gauge factors ranged from 7.49-14.85 for 3 wt.%, 9.84-30.8 for 4 wt.%, and 0.56-9.16 for 5 wt.% rGO, establishing these samples as effective piezoresistive sensors for bioengineering applications. It was also concluded that the manufactured composites exhibited good linearity and piezoresistive performance in the 1.54-2.87% strain range, some stability in the 100 cycle 3-point bending tests, the tensile strength varied from 1.05 MPa to 3.084 MPa, the degradation temperature ranged from 380 °C to 410 °C, as well as composites reversibly losing their electrical component before the structure integrity was lost, when tensile tested. Lastly, two proofs of concept were developed, where real-time acquisition and monitoring of data related to joint movements and breathing patterns was successfully performed in volunteers.

2024Conference object

Open access

3D Printed Robotic Hand with Piezoresistive Touch Capability

Publication . Fonseca, Gonçalo; Nunes-Pereira, João; Silva, Abilio

This work proposes the design of a low-cost sensory glove system that complements the operation of a 3D-printed mechanical hand prosthesis, providing it with the ability to detect touch, locate it and even measure the intensity of associated forces. Firstly, the production of the prosthetic model was performed using 3D printing, which allowed for quick and cheap production of a robotic hand with the implementation of a mechanical system that allows controlled movements with high performance and with the possibility of easily replacing each piece individually. Secondly, we performed the construction and instrumentation of a complementary sensory mimicry add-on system, focusing on the ability to sense touch as the primary target. Using piezoresistive sensors attached to the palm of the glove, a multi-sensor system was developed that was able to locate and quantify forces exerted on the glove. This system showed promising results and could be used as a springboard to develop a more complex and multifunctional system in the future.

2023Journal article

Open access