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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

(a) Current versus voltage of humidity sensor at three different temperatures; (b)Humidity sensing response at room temperature with eight different  levels; (c) Sensing response under three different temperature conditions (room temperature, 40 °C and 70 °C); (d) Humidity sensing varies with the amount of deposited graphene.
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f6: (a) Current versus voltage of humidity sensor at three different temperatures; (b)Humidity sensing response at room temperature with eight different levels; (c) Sensing response under three different temperature conditions (room temperature, 40 °C and 70 °C); (d) Humidity sensing varies with the amount of deposited graphene.

Mentions: where and are the diameter and thickness of the platelets, respectively, and is the interplatelet distance. If is shorter than the electron hopping distance through the non-conducting matrix, electron hopping takes place, facilitating formation of conductive pathways. The limit for single-step electron hopping is ~10 nm 71. Multistep electron hopping may take place for >10 nm. A critical value of ~1 μm has been reported for some polymers with conductive fillers7172. With ~4.5 nm average flake thickness and ~204 nm average lateral dimension estimated from AFM measurements and considering d* ~ 10 nm-1 μm, we get v0 ~ 0.486–0.003. This requires  > 0.486 to ensure a conductive graphene-PVP composite. Bulk density of graphite is ~2.3 gcm−3. However, exfoliated graphene flakes can have a significantly lower density. Commercial graphene samples are typically quoted to have a density ranging from 0.03–0.4 gcm−3 73. Assuming 0.4 gcm−3 for our UAPLE graphene, a >0.047 gL−1 concentration of graphene ink is required to form a conductive graphene-PVP composite. We stress that this estimation is dependent on further experimental determination of of PVP and the density of UALPE graphene. The graphene-PVP composite (v ~ 0.889) formed from this graphene ink (c ~ 0.40 gL−1) is therefore predicted to be conductive. This is experimentally confirmed with resistance measurement between the IDEs at room temperature, 40 °C and 70 °C, as shown in Fig. 6(a). The linear relationship confirms good Ohmic contact between the graphene-PVP composite and the gold IDEs. A control experiment is conducted by inkjet printing pure PVP solution, which shows negligible electrical conductivity, as expected.


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)

(a) Current versus voltage of humidity sensor at three different temperatures; (b)Humidity sensing response at room temperature with eight different  levels; (c) Sensing response under three different temperature conditions (room temperature, 40 °C and 70 °C); (d) Humidity sensing varies with the amount of deposited graphene.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: (a) Current versus voltage of humidity sensor at three different temperatures; (b)Humidity sensing response at room temperature with eight different levels; (c) Sensing response under three different temperature conditions (room temperature, 40 °C and 70 °C); (d) Humidity sensing varies with the amount of deposited graphene.
Mentions: where and are the diameter and thickness of the platelets, respectively, and is the interplatelet distance. If is shorter than the electron hopping distance through the non-conducting matrix, electron hopping takes place, facilitating formation of conductive pathways. The limit for single-step electron hopping is ~10 nm 71. Multistep electron hopping may take place for >10 nm. A critical value of ~1 μm has been reported for some polymers with conductive fillers7172. With ~4.5 nm average flake thickness and ~204 nm average lateral dimension estimated from AFM measurements and considering d* ~ 10 nm-1 μm, we get v0 ~ 0.486–0.003. This requires  > 0.486 to ensure a conductive graphene-PVP composite. Bulk density of graphite is ~2.3 gcm−3. However, exfoliated graphene flakes can have a significantly lower density. Commercial graphene samples are typically quoted to have a density ranging from 0.03–0.4 gcm−3 73. Assuming 0.4 gcm−3 for our UAPLE graphene, a >0.047 gL−1 concentration of graphene ink is required to form a conductive graphene-PVP composite. We stress that this estimation is dependent on further experimental determination of of PVP and the density of UALPE graphene. The graphene-PVP composite (v ~ 0.889) formed from this graphene ink (c ~ 0.40 gL−1) is therefore predicted to be conductive. This is experimentally confirmed with resistance measurement between the IDEs at room temperature, 40 °C and 70 °C, as shown in Fig. 6(a). The linear relationship confirms good Ohmic contact between the graphene-PVP composite and the gold IDEs. A control experiment is conducted by inkjet printing pure PVP solution, which shows negligible electrical conductivity, as expected.

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