Abstract:We propose a flexible wireless pressure sensor, which uses a graphene/polydimethylsiloxane (GR/PDMS) sponge as the dielectric layer. The sponge is sandwiched between two surfaces of a folded flexible printed circuit with patterned Cu as the antenna and electrode. By adjusting graphene and NH
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“…At present, composites are used in a wide range of applications, including strain sensors, electronic displays, optical attenuators and smart windows [4][5][6][7][8][9][10]. Composites, which use carbon materials in high-performance applications, have been widely used owing to their strengthening effect, high stiffening and feasible preparation, such as graphene oxide-silica nanohybrid [11][12][13][14][15][16], graphene/polydimethylsiloxane [17,18] and polylactic acid (PLA) as a host polymer and different forms of carbon fillers [19,20]. Considerable progress has already been made in these fields.…”
In this paper we introduce a polydimethylsiloxane (PDMS) composite fabricated using a simple production process and demonstrate the optical transmittance properties of this composite in the 300–1000 nm wavelength region. We control the material’s transmittance by varying the microcrystalline graphite powder concentration or the composite film’s thickness. In addition, we tailor the specimens into various trapezoidal shapes and load these specimens by mechanically stretching them in the direction perpendicular to both their base lines and their top lines. The advantage of this method is that a wide range of transmittance properties can be obtained for a given specimen. Furthermore, samples with different trapezoidal shapes have different transmittance tuning capabilities.
“…At present, composites are used in a wide range of applications, including strain sensors, electronic displays, optical attenuators and smart windows [4][5][6][7][8][9][10]. Composites, which use carbon materials in high-performance applications, have been widely used owing to their strengthening effect, high stiffening and feasible preparation, such as graphene oxide-silica nanohybrid [11][12][13][14][15][16], graphene/polydimethylsiloxane [17,18] and polylactic acid (PLA) as a host polymer and different forms of carbon fillers [19,20]. Considerable progress has already been made in these fields.…”
In this paper we introduce a polydimethylsiloxane (PDMS) composite fabricated using a simple production process and demonstrate the optical transmittance properties of this composite in the 300–1000 nm wavelength region. We control the material’s transmittance by varying the microcrystalline graphite powder concentration or the composite film’s thickness. In addition, we tailor the specimens into various trapezoidal shapes and load these specimens by mechanically stretching them in the direction perpendicular to both their base lines and their top lines. The advantage of this method is that a wide range of transmittance properties can be obtained for a given specimen. Furthermore, samples with different trapezoidal shapes have different transmittance tuning capabilities.
“…The fatigue could also be justified by signatures seen in Raman spectroscopy (see Figure S10, Supporting Information) where the CC bonds (from D and G bands) do not show bands shifting due to the stress transmission that produces carbon bond elongation. This concludes that there is no adhesion between the nonfunctionalized graphene flakes and the polymer matrix after pressing (the nonfunctionalized graphene flakes are not wettable), which also associate the presence of micro nanocavities around the flakes by the solvent. The importance of the surface properties of the embedded flakes on the creation of microcavities and as such on the conductivity of the composite was verified by testing samples containing graphene oxide (0.6 wt%) with the surface that are more polar, in comparison to graphene, and more wettable by the solvent.…”
Colloidal liquid metal alloys of gallium, with melting points below room temperature, are potential candidates for creating electrically conductive and flexible composites. However, inclusion of liquid metal micro‐ and nanodroplets into soft polymeric matrices requires a harsh auxiliary mechanical pressing to rupture the droplets to establish continuous pathways for high electrical conductivity. However, such a destructive strategy reduces the integrity of the composites. Here, this problem is solved by incorporating small loading of nonfunctionalized graphene flakes into the composites. The flakes introduce cavities that are filled with liquid metal after only relatively mild press‐rolling (<0.1 MPa) to form electrically conductive continuous pathways within the polymeric matrix, while maintaining the integrity and flexibility of the composites. The composites are characterized to show that even very low graphene loadings (≈0.6 wt%) can achieve high electrical conductivity. The electrical conductance remains nearly constant, with changes less than 0.5%, even under a relatively high applied pressure of >30 kPa. The composites are used for forming flexible electrically‐conductive tracks in electronic circuits with a self‐healing property. The demonstrated application of co‐fillers, together with liquid metal droplets, can be used for establishing electrically‐conductive printable‐composite tracks for future large‐area flexible electronics.
“…The SRR structures provide compact designs for the antennas enabling device miniaturization as well as array and batch processing.Fig. 9Wireless pressure sensors (i) GR/PDMS sponge based pressure sensor with attached LC circuit (Reproduced by permission from [190] Copyright 2019,Nature ) (ii) Fabric spacer based capacitive sensor with a ferrite film and LC passive antenna (Reproduced by permission from [180] Copyright 2019, Wiley ) (iii) Tape based sensor fabrication and final integrated antenna based sensor (Reproduced by permission from [176] Copyright 2009, American Institute of Physics ) (iv) Biodegradable micropyramidal patterned sensor with RF data transmission (Reproduced by permission from [181] Copyright 2019,Nature ) (v) Schematic of external in vivo pressure measurement (Reproduced by permission from [191] Copyright 2005,Elsevier ) (vi) Diaphragm based wireless antenna integrated sensor…”
Section: Evolution Of Sensor Device Architecturementioning
Sensors are becoming more demanding in all spheres of human activities for their advancement in terms of fabrication and cost. Several methods of fabrication and configurations exist which provide them myriad of applications. However, the advantage of fabrication for sensors lies with bulk fabrication and processing techniques. Exhaustive study for process advancement towards miniaturization from the advent of MEMS technology has been going on and progressing at high pace and has reached a highly advanced level wherein batch production and low cost alternatives provide a competitive performance. A look back to this advancement and thus understanding the route further is essential which is the core of this review in light of nanomaterials and printed technology based sensors. A subjective appraisal of these developments in sensor architecture from the advent of MEMS technology converging present date novel materials and process technologies through this article help us understand the path further.
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