Structured elastomeric submillimeter films displaying magneto and piezo resistivity

Abstract

Structured elastomer films (100-150 mm) presenting piezo and magneto resistance are described. The films are composites of filler particles, which are both electrically conductive and magnetic, dispersed in an elastomeric matrix. The particles consist of magnetite (6 nm) grouped in silver-coated aggregates (Fe 3 O 4 @Ag). The matrix is styrene-butadiene rubber (SBR) in which diethylene glycol (DEG) is added. The particles, SBR and DEG, are dispersed in toluene and then placed between two rare earth magnets. Formation of pseudo-chains (needles) of inorganic material aligned in the direction of the magnetic field is obtained after solvent evaporation. The addition of DEG is substantial to obtain an electrically conductive material. The electrical conductivity is anisotropic and increases when applying normal stresses and/or magnetic fields in the direction of the needles. The elastomers, particles, and needless were characterized by XRD, SEM, EDS, FTIR, DSC, TGA, VSM, profilometry, and stress-strain analysis.V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 00, 000-000 KEYWORDS: composites; elastomers; magnetoresistive composites; piezoresistive elastomers; sensors; structured elastomers INTRODUCTION Structured elastomer composites with anisotropic properties, such as magneto and piezoresistivity, are becoming of great interest for their potential applications in physical sensors, flexible devices, and electronic connectors. [1][2][3][4][5][6][7][8][9] In addition to common challenges for technological application of smart materials (obtaining appropriated quality parameters), there are specific difficulties in the case of structured elastomeric composites: (i) to develop ohmic contacts with good adherence to the elastomer; (ii) to obtain a reversible response (dependent on the elastic behavior); and (iii) to prepare submillimeter films displaying the physical properties of interest. The first two issues (contacts and reversibility) have been addressed in previous works of our group, using magnetorheological elastomers based on dispersions of magnetic nanomaterials in polydimethylsiloxane

Well-ordered “tooth-shaped” silver-microstructures on poly(methyl methacrylate) patterned by laser writing

“…Ordered metal based microstructures can find potential applications in bioactive materials [16], structures with plasmonic properties [17], materials with magneto and piezo resistivity [18], surfaces with shape-memory [19] and catalytic materials [20].…”

Anisotropic reversible piezoresistivity in magnetic–metallic/polymer structured elastomeric composites: modelling and experiments

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“…1,[5][6][7]11 First, magnetic nanoparticles (NPs) in the superparamagnetic regime are synthesized. 1,[5][6][7]11 First, magnetic nanoparticles (NPs) in the superparamagnetic regime are synthesized.…”

“…TEA is a crucial property in devices like extended pressure mapping sensors 1,5,7 and Zebra R -like connectors for parallel flipchip connections. it is possible to obtain electrical conduction only in the direction of H curing (no measurable conduction in the orthogonal direction).…”

Magneto-piezoresistivity in iron particle-filled silicone: An alternative outlook for reading magnetic field intensity and direction

“…On the other hand, composites made of magnetic particles homogeneously dispersed into an elastic matrix (generally known as magnetorheologic materials) present improved mechanical, thermal and magneto-electric properties under the application of an external magnetic field, during the production or onto the produced composite [11][12][13][14]. In particular, the inverse elastomagnetic effect is exhibited: strain appears when its state of magnetization is changed, due to the alignment or rotation of magnetic particles and it is not depending on the intrinsic magnetostriction of the particles [15][16][17][18][19].…”