Temperature-dependent conductive composites: poly(N-isopropylacrylamide-co-N-methylol acrylamide) and carbon black composite films

Chuang, Wen-Ju; Chiu, Wen‐Yen; Tai, H.

doi:10.1039/c2jm33601d

Cited by 25 publications

(22 citation statements)

References 17 publications

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“…Many previously reported devices have used a vertical structure where the polymer PTC film is sandwiched between two electrodes (denoted as the vertical-type sensor). Here, we demonstrate a lateral-type sensor where the polymer PTC is printed across two neighboring electrodes (16,23). Both sensor types exhibit similar initial resistivity changes of six orders of magnitude over a temperature change of only 4°C.…”

Section: Resultsmentioning

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: Resultsmentioning

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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“…24 However, the conductive llers were embedded in the polymer matrix in Chuang's work whereas the silver particles were attached to the bers surface in our case. However, as the temperature exceeded 42 C, the resistance dropped by $60% for a temperature change of only 4 C, exhibiting a very high sensitivity to the change of temperature.…”

Section: Characterization Of P(nipam-co-nma)/ag Composite Bersmentioning

confidence: 64%

“…23,24 The preparation procedure is shown in Scheme 1. 23,24 The preparation procedure is shown in Scheme 1.…”

Section: Synthesis Of Poly(nipam-co-nma)mentioning

confidence: 99%

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Thermally responsive behaviour of the electrical resistance of electrospun P(NIPAm-co-NMA)/Ag composite nanofibers

Zhang

Deng

et al. 2015

RSC Adv.

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Thermally responsive copolymer P(NIPAm-co-NMA) was prepared via a radical copolymerization and spun into nanofibers using electrospinning. After thermal crosslinking, the electrospun fibers were modified using KH590 and silver nanoparticles were introduced onto the fiber surface using a chemical plating method.The electrical resistance of the composite fibers containing 65.5% of silver at different temperatures was investigated and it was found that the resistance dropped by $60% as the temperature increased from 42 C to 46 C, which is consistent with the solubility transition of PNIPAm with the change of temperature as revealed by differential scanning calorimetry (DSC) measurement.

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“…The synthesized PNN copolymer was thus capable of cross-linking at high temperatures. 12 The thermoresponsive PNN copolymer was then mixed with the conductive PEDOT:PSS in water to prepare the sheath solution for electrospinning. On the other hand, poly(butyl acrylate-co-styrene) copolymer (PBS) was synthesized by soapless emulsion polymerization which was selected to provide the flexibility of the composite fiber.…”

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confidence: 99%

Preparation and properties of thermoresponsive and conductive composite fibers with core‐sheath structure

Lin

Don

Chang

et al. 2015

J. Polym. Sci. Part A: Polym. Chem.

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In this research, thermoresponsive and conductive fibers with core-sheath structure were fabricated by coaxial electrospinning. For preparing the spinning sheath solution, poly-(N-isopropylacrylamide-co-N-methylolacrylamide) (PNN) copolymer having thermoresponsive and cross-linkable properties was synthesized by free-radical polymerization using redox initiators; it was then mixed with the conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) at different weight ratios in water. On the other hand, poly(butyl acrylate-co-styrene) (PBS) copolymer synthesized by emulsion polymerization was dissolved in chloroform and used as the spinning core solution. After electrospinning, the fibers were treated at 110 8C for 1 h to cross-link the PNN portion in the sheath for strengthening the fibers. Well-defined core-sheath fibers were observed from SEM pictures; the outside and inside (core) diameters were 568 6 24 and 290 6 40 nm, respectively, as determined from TEM pictures. The fiber mats were further doped by DMSO to enhance their conductivity. For the fiber mat with the weight ratio of PEDOT:PSS/PNN at 0.20 in the sheath, its surface conductivity could reach 29.4 S/ cm. In addition, the fiber mats exhibited thermoresponsive properties that both swelling ratio and electric resistance decreased with temperature. Furthermore, the fiber mats exhibited improved flexibility as evaluated via bending test.

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Temperature-dependent conductive composites: poly(N-isopropylacrylamide-co-N-methylol acrylamide) and carbon black composite films

Cited by 25 publications

References 17 publications

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

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

Thermally responsive behaviour of the electrical resistance of electrospun P(NIPAm-co-NMA)/Ag composite nanofibers

Preparation and properties of thermoresponsive and conductive composite fibers with core‐sheath structure

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