Glass transition temperature as a guide to selection of polymers suitable for PTC materials

Meyer, John C.

doi:10.1002/pen.760130611

Cited by 260 publications

(150 citation statements)

References 12 publications

(2 reference statements)

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“…Extraordinarily large resistivity changes can eliminate the need for per-pixel amplification circuitry, as the output signal of the sensor can be directly multiplexed and fed to external recording equipment, ultimately reducing device complexity and manufacturing costs. The PTC effect in conductive-filled polymers results from an increase in the specific volume as the temperature increases, typically during progression through the melting point of crystalline regions (17,18). For this reason, resistivity is changed drastically by change in temperature for only a few degrees.…”

Section: Significancementioning

confidence: 99%

Ultraflexible, large-area, physiological temperature sensors for multipoint measurements

Yokota

Inoue

Terakawa

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

339

298

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We report a fabrication method for flexible and printable thermal sensors based on composites of semicrystalline acrylate polymers and graphite with a high sensitivity of 20 mK and a high-speed response time of less than 100 ms. These devices exhibit large resistance changes near body temperature under physiological conditions with high repeatability (1,800 times). Device performance is largely unaffected by bending to radii below 700 μm, which allows for conformal application to the surface of living tissue. The sensing temperature can be tuned between 25°C and 50°C, which covers all relevant physiological temperatures. Furthermore, we demonstrate flexible active-matrix thermal sensors which can resolve spatial temperature gradients over a large area. With this flexible ultrasensitive temperature sensor we succeeded in the in vivo measurement of cyclic temperatures changes of 0.1°C in a rat lung during breathing, without interference from constant tissue motion. This result conclusively shows that the lung of a warm-blooded animal maintains surprising temperature stability despite the large difference between core temperature and inhaled air temperature. T emperature control plays a very important role in homeostasis, and body temperature varies both spatially and temporally in an effort to transfer heat between the living body and the environment via skin and respiratory organs. Accurate measurement of localized temperature changes in soft tissue regardless of large-scale motion is important in understanding thermal phenomena of homeostasis and realizing future sophisticated health diagnostics (1-3). Therefore, flexible temperature sensors which softly interface with tissue have been investigated frequently for applications in the medical field. However, these applications require the combination of sensitivity, fast response time, stability in physiological environments, and multipoint measurement. Before this work, to our knowledge, no experiment has simultaneously demonstrated orders-of-magnitude changes in electrical properties (sensitivity) repeatedly at varying physiological temperatures and conditions (stability) in a robust, easy-to-fabricate, flexible temperature sensor (processability).When sensors and electronics are directly attached to the surface of an animal body, the use of soft and flexible electronic devices is expected to reduce mechanical stress induced on the body. From this viewpoint, the field of flexible electronics has attracted much attention recently. The ability to gather information such as pressure and temperature from curvilinear and dynamic surfaces without impairing the movement or usability of the users is unmatched by conventional silicon electronics. There have been reports of the potential application of flexible electrodes on ultrathin substrates (4), flexible sensors that measure biological signals, electrocardiograms, temperature, pressure (5, 6), organic amplifier systems (7), high-sensitivity pressure sensors (8), and ultrathin and imperceptible devices (9, 10).To meas...

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Section: Significancementioning

confidence: 99%

Ultraflexible, large-area, physiological temperature sensors for multipoint measurements

Yokota

Inoue

Terakawa

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

339

298

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“…As the CB concentration gradually decreased, the dimensions of conductive pathways get narrower and even not continuous. The main conductive mechanism transformed from ohmic conduction to quantum tunneling conduction where conductivity is mainly the result of electron tunneling through small gap distances separating the CB particles and their aggregates [1]. When the width of the gaps increases by thermal expansion of PTFE matrix, the electron tunneling probability will diminish, which results in a strong PTC effect.…”

Section: Resultsmentioning

confidence: 99%

“…Polymer resins are excellent electrical insulators, however, they can become conductive composites when blended with some kinds of conductive fillers (e.g., carbon black, carbon fiber and metal powders), the critical amount of filler necessary to build up a continuous conductive network and accordingly to make the material conductive is referred to as the percolation threshold [1][2].…”

Section: Introductionmentioning

confidence: 99%

Positive temperature coefficient effects of carbon blackfilled polytetrafluoroethylene composites

2009

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Carbon black (CB)-filled polytetrafluoroethylene (PTFE) composites were prepared by compact molding of a dry-mixture of CB and polymer powders followed by a sintering technology. The composites show a very low percolation threshold about 5 vol. %, which can be attributed to the segregated distribution of CB in the interfacial regions of PTFE particles. The PTFE/CB composites exhibit a high PTC transition temperature (>300 0 C), high PTC intensity (3.5) and no NTC effects. The absence of NTC effect of the composites was attributed to the extremely high viscosity of PTFE at temperatures above its melting point, which restricts the migration of CB particles and prevents the formation of new conductive networks.

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“…Low density polyethylene has a PTC magnitude of 3.5 orders of magnitude while high density polyethylene has a PTC of 4.5 orders [56]. In addition, a polymer with a narrow melting temperature range has a steep PTC transition [45].…”

Section: Carbon Black-semlcrystallne Composite Themistorsmentioning

confidence: 99%

“…Meyer assumes that crystalline polymer regions (300 A) separate the conduction particles [56,60]. Electron tunneling through these regions is easier than tunneling through similar amorphous regions.…”

Section: Carbon Black-semlcrystallne Composite Themistorsmentioning

confidence: 99%

Nanocomposites for Electronic Applications. Volume 3

Cross

1993

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Glass transition temperature as a guide to selection of polymers suitable for PTC materials

Cited by 260 publications

References 12 publications

Ultraflexible, large-area, physiological temperature sensors for multipoint measurements

Ultraflexible, large-area, physiological temperature sensors for multipoint measurements

Positive temperature coefficient effects of carbon blackfilled polytetrafluoroethylene composites

Nanocomposites for Electronic Applications. Volume 3

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