Sensors and actuators

 

The work is focused on piezoelectric, piezoresistive and magnetoelectric sensors and actuators.

  • Development of strain and deformation sensors based on polymer composites. The conductivity and piezoresistive response of the materials will be tuned by the introduction of specific fillers such as carbonaceous fillers and/or metallic nanoparticles.
  • Development of magnetic and magnetoelectric materials based on organic/inorganic hybrid structures and inorganic thin films. These materials are at the basis of the development of magnetic and current sensors, among others.
  • Development of electronic and ionic electroactive actuators based both on polymer composites and polymer blends. The main objective is the fine control of actor force, displacement and time response.
  • A recent research involves the development of active fillers for (bio)chemical sensing

 

Piezoelectric Sensors     Piezoresistive Sensors   Magnetoelectric Sensors

 

Chemical Sensors        Devices/Applications Development

 

Main References

 

Piezoelectric Sensors

Fig1 Sensors Vanessa

Photograph of a transparent P(VDF-TrFE) based-piezoelectric transducer with patterned AZO electrodes.

  Piezoresistive Sensors 

figure 1 Sensors Armando

Schematic representation of the 4-point bending tests: z is the vertical displacement of the piston, d is the thickness of the sample (~1 mm) and a is the distance between the first and the second bending points (15 mm) and l the distance between the lower supports (45 mm).

 


figure 2 Sensors Armandofigure 3 Sensors Armandofigure 4 Sensors Armando

(a)                                                       (b)                                                   (c)

(a) Concentration dependence of the electrical conductivity for the different CNT/PVDF composites; (b) Cyclic piezoresistive response as a function of time for the following conditions: bending of 1 mm, deformation velocity of 2 mm min-1 at room temperature; (c) Relative resistance variation vs. strain curves and the corresponding fit for the determination of the Gauge Factor.

 


2 Sensors PedroC

 

Piezoresistive extruded composites to small and large strains applied in hand glove to measure fingers movement with the developed electronic data acquisition is it possible to visualize in real time and to analyze the sensor measurements.

 


Printing1 Sensors VitorC

 

Picture of the inkjet printing piezoresistive matrix sensor and mechanical deformation signal and amplitude response of three sensors.

  Magnetoelectric Sensors

 

2a Devices PedroL 2b Devices PedroL

(a)                                                                                                                                                     (b)

a) Picture of a flexible PVDF/Vitrovac unimorph laminate. b) Representation of the ME magnetic field sensing device.
Traditional magnetic sensors like Hall or magnetoresistive sensors need power supply, which raises some limitations. In this context, self-powered magnetic field sensors that directly transfer magnetic energy into electric signals are of large interest and can be realized thanks to the ME effect. This new kind of ME magnetic sensors also have enormous potential as by-products related to magnetic sensors: electric current sensors, speed sensors, angular sensors, electronic steering, throttle control, battery management, vehicle transmission, digital compasses, and GPS devices are just some examples and many of them are already being studied.
The highest ME response of 45V/cm.Oe obtained for a PVDF (100µm thick)/Vitrovac laminate (Figure a) as well as the possibility to optimize such value as indicated by the Finite Element Model, make this laminate an excellent candidate to be used as applications such as sensors (Figure b), energy harvester devices and memories [1, 2]. 

Fig Devices Pedro L

Schematic representation of the Vitrovac/Epoxy/PVDF composite (a) and its ME response after optimization that pave do way into its incorporation into technological applications such as magnetic sensors.
ME response of the ME structures is studied as a function of the PVDF, magnetostrictive component and epoxy properties; results are theoretically evaluated with final goal to incorporate such materials on innovative technological applications such magnetic sensors.

  Chemical Sensors

 

Fig1 Devices Catarina L

Scheme of polymer dipoles interaction with diferente Ag nanoparticles size: 6 nm, 27 nm and 60 nm, responsible for the electroactive phase crystallization of the PVDF polymer.

 

Fig2 Devices Catarina L

 

Different zeolite-type microposorus materials used on the production of sensors.

 

Devices/Applications Development

1 Sensors PedroC

Large strain piezoresistive sensors, until 20% strain, of CNT/SBS composites processed by different scales techniques. Linear variation between electrical resistance with applied strain to conductive composites during several cycles with high gauge factor.

 


Printing2 Sensors VitorC

 

Inkjet Piezoresistive sensor matrix: design of the different pattern layers needed for the printing of the sensor matrix and Printed sensor matrix final result.

 

IL3 Catarina Lopes

PVDF-Ionic Liquid actuator bending response to voltages up to +/- 5 V (below) and proposed mechanism (above).

Main References

  • V. F. Cardoso, G. Minas, S. Lanceros-Mendez - Multi layer spin-coating deposition of poly(vinylidene fluoride) films for controlling thickness and piezoelectric response. Sensors and Actuators A-physical, Vol. 192 (2013), pp. 76-80. Doi: 10.1016/j.sna.2012.12.019.
  • V. F. Cardoso, C. M. Costa, G. Minas,S. Lanceros-Mendez - Improving optical and electroactive response of poly(vinylidene fluoride-trifluoroethylene) spin coated films for sensor and actuator applications. IOP Science – Smart Materials and Structures. Vol. 21 (2012) 085020. Doi: 10.1088/0964-1726/21/8/085020. 
  • V. F. Cardoso, C. M. Costa, C. J. Tavares, G. Minas, S. Lanceros-Méndez. Micro and nanofilms of poly(vinylidene fluoride) with controlled thickness, morphology and electroactive crystalline phase for sensors and actuators applications. IOP Science – Smart Materials and Structures. Vol. 20 (2011) 087002. Doi: 10.1088/0964-1726/20/8/087002. 
  • Ferreira A, Martínez MT, Ansón-Casaos A, Gómez-Pineda LE, Vaz F, Lanceros-Mendez S. Relationship between electromechanical response and percolation threshold in carbon nanotube/poly(vinylidene fluoride) composites. Carbon. 2013(0)
  • Gonzalez-Dominguez JM, Anson-Casaos A, Martinez MT, Ferreira A, Vaz F, Lanceros-Mendez S. Piezoresistive response of Pluronic-wrapped single-wall carbon nanotube-epoxy composites. Journal of Intelligent Material Systems and Structures. 2012;23(8):909
  • Ferrreira A, Rocha JG, Ansón-Casaos A, Martínez MT, Vaz F, Lanceros-Mendez S. Electromechanical performance of poly(vinylidene fluoride)/carbon nanotube composites for strain sensor applications. Sensors and Actuators A: Physical. 2012;178(0):10-6
  • Ferreira A, Cardoso P, Klosterman D, Covas JA, van Hattum FWJ, Vaz F, et al. Effect of filler dispersion on the electromechanical response of epoxy/vapor-grown carbon nanofiber composites. Smart Materials and Structures. 2012;21(7).
  • Costa P, Silvia C, Viana JC, Lanceros Mendez S. Extruded thermoplastic elastomers styrene–butadiene–styrene/carbon nanotubes composites for strain sensor applications. Composites Part B: Engineering. 2014;57(0):242-9.
  • Costa P, Silva J, Sencadas V, Simoes R, Viana JC, Lanceros-Méndez S. Mechanical, electrical and electro-mechanical properties of thermoplastic elastomer styrene–butadiene–styrene/multiwall carbon nanotubes composites. J Mater Sci. 2013;48(3):1172-9.
  • Costa P, Ferreira A, Sencadas V, Viana JC, Lanceros-Méndez S. Electro-mechanical properties of triblock copolymer styrene–butadiene–styrene/carbon nanotube composites for large deformation sensor applications. Sensors and Actuators A: Physical. 2013;201(0):458-67.
  • V. Correia, C. Caparros, C. Casellas, L. Francesch, J. G. Rocha, and S. Lanceros-Mendez."Development of inkjet printed strain sensors".Smart Materials and Structures, Struct. 22 105028,DOI: 10.1088/0964-1726/22/10/105028, 2013.
  • Martins, P. and S. Lanceros-Méndez, Polymer-based Magnetoelectronic Materials. Advanced Functional Materials, 2013.
  • Silva, M., et al., Optimization of the Magnetoelectric Response of Poly(vinylidene fluoride)/Epoxy/Vitrovac Laminates. ACS Applied Materials & Interfaces, 2013.
  • Lopes, A.C., Carabineiro, S.A.C., Pereira, M.F.R., Botelho, G., Lanceros-Mendez, S., (2013) Nanoparticle size and concentration dependence of the electroactive phase content and electrical and optical properties of Ag/poly(vinylidene fluoride) composites, ChemPhysChem, 14 (9):1926-1933.