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CMOS integration of inkjet-printed graphene for humidity sensing.

Santra S, Hu G, Howe RC, De Luca A, Ali SZ, Udrea F, Gardner JW, Ray SK, Guha PK, Hasan T - Sci Rep (2015)

Bottom Line: The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer.When the sensors are exposed to relative humidity ranging from 10-80%, we observe significant changes in resistance with increasing sensitivity from the amount of graphene in the inks.Our sensors show excellent repeatability and stability, over a period of several weeks.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Indian Institute of Technology, Kharagpur, 721302, India.

ABSTRACT
We report on the integration of inkjet-printed graphene with a CMOS micro-electro-mechanical-system (MEMS) microhotplate for humidity sensing. The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer. We formulate inks with different graphene concentrations, which are then deposited through inkjet printing over predefined interdigitated gold electrodes on a CMOS microhotplate. The graphene flakes form a percolating network to render the resultant graphene-PVP thin film conductive, which varies in presence of humidity due to swelling of the hygroscopic PVP host. When the sensors are exposed to relative humidity ranging from 10-80%, we observe significant changes in resistance with increasing sensitivity from the amount of graphene in the inks. Our sensors show excellent repeatability and stability, over a period of several weeks. The location specific deposition of functional graphene ink onto a low cost CMOS platform has the potential for high volume, economic manufacturing and application as a new generation of miniature, low power humidity sensors for the internet of things.

No MeSH data available.


Related in: MedlinePlus

AFM characterizations of graphene flakes: (a) and (b) micrographs of typical flakes, the scale bar is 200 nm; (c) and (d) height variations across (a) and (b), respectively; (e) thickness distribution.
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f4: AFM characterizations of graphene flakes: (a) and (b) micrographs of typical flakes, the scale bar is 200 nm; (c) and (d) height variations across (a) and (b), respectively; (e) thickness distribution.

Mentions: The graphene flakes are characterized with Atomic Force Microscopy (AFM). The sample for AFM is prepared by dip-coating a Si/SiO2 wafer into a graphene dispersion diluted to 2 vol% by pure IPA. Though the concentration of PVP in this diluted dispersion is ~3.8 × 10−4 wt%, the residual polymer prevents accurate measurement of the flake dimensions. The sample is therefore annealed at 400 °C for 30 min. This temperature is chosen because PVP starts to decompose at this temperature in air59 while the exfoliated graphene flakes remain stable6061. The annealed sample is imaged with a Bruker Dimension Icon AFM in ScanAsystTM mode, using a silicon cantilever with a Si3N4 tip. Micrographs of typical flakes are shown in Fig. 4(a,b), along with the height variations across the samples; Fig. 4(c,d). The thickness distribution of flakes is also measured; Fig. 4(e). This shows that 63% of the flakes have thicknesses <5 nm, corresponding to <13 layers, assuming ~0.7 nm measured thickness for the bottom layer and ~0.35 nm increase in thickness for each additional layer62. The average flake lateral dimension is ~204 nm. Note that the number of layers obtained in IPA/PVP is higher than what is typically obtained by UALPE of graphite in water/SDC, with ~26% mono- and ~22% bi-layer, and with 300–600 nm average lateral dimension from similar experimental parameters47.


CMOS integration of inkjet-printed graphene for humidity sensing.

Santra S, Hu G, Howe RC, De Luca A, Ali SZ, Udrea F, Gardner JW, Ray SK, Guha PK, Hasan T - Sci Rep (2015)

AFM characterizations of graphene flakes: (a) and (b) micrographs of typical flakes, the scale bar is 200 nm; (c) and (d) height variations across (a) and (b), respectively; (e) thickness distribution.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663628&req=5

f4: AFM characterizations of graphene flakes: (a) and (b) micrographs of typical flakes, the scale bar is 200 nm; (c) and (d) height variations across (a) and (b), respectively; (e) thickness distribution.
Mentions: The graphene flakes are characterized with Atomic Force Microscopy (AFM). The sample for AFM is prepared by dip-coating a Si/SiO2 wafer into a graphene dispersion diluted to 2 vol% by pure IPA. Though the concentration of PVP in this diluted dispersion is ~3.8 × 10−4 wt%, the residual polymer prevents accurate measurement of the flake dimensions. The sample is therefore annealed at 400 °C for 30 min. This temperature is chosen because PVP starts to decompose at this temperature in air59 while the exfoliated graphene flakes remain stable6061. The annealed sample is imaged with a Bruker Dimension Icon AFM in ScanAsystTM mode, using a silicon cantilever with a Si3N4 tip. Micrographs of typical flakes are shown in Fig. 4(a,b), along with the height variations across the samples; Fig. 4(c,d). The thickness distribution of flakes is also measured; Fig. 4(e). This shows that 63% of the flakes have thicknesses <5 nm, corresponding to <13 layers, assuming ~0.7 nm measured thickness for the bottom layer and ~0.35 nm increase in thickness for each additional layer62. The average flake lateral dimension is ~204 nm. Note that the number of layers obtained in IPA/PVP is higher than what is typically obtained by UALPE of graphite in water/SDC, with ~26% mono- and ~22% bi-layer, and with 300–600 nm average lateral dimension from similar experimental parameters47.

Bottom Line: The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer.When the sensors are exposed to relative humidity ranging from 10-80%, we observe significant changes in resistance with increasing sensitivity from the amount of graphene in the inks.Our sensors show excellent repeatability and stability, over a period of several weeks.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Indian Institute of Technology, Kharagpur, 721302, India.

ABSTRACT
We report on the integration of inkjet-printed graphene with a CMOS micro-electro-mechanical-system (MEMS) microhotplate for humidity sensing. The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer. We formulate inks with different graphene concentrations, which are then deposited through inkjet printing over predefined interdigitated gold electrodes on a CMOS microhotplate. The graphene flakes form a percolating network to render the resultant graphene-PVP thin film conductive, which varies in presence of humidity due to swelling of the hygroscopic PVP host. When the sensors are exposed to relative humidity ranging from 10-80%, we observe significant changes in resistance with increasing sensitivity from the amount of graphene in the inks. Our sensors show excellent repeatability and stability, over a period of several weeks. The location specific deposition of functional graphene ink onto a low cost CMOS platform has the potential for high volume, economic manufacturing and application as a new generation of miniature, low power humidity sensors for the internet of things.

No MeSH data available.


Related in: MedlinePlus