High-performance capacitive humidity sensor with novel electrode and polyimide layer based on MEMS technology

Kim, Ji Eun; Hong, Sungmin; Moon, Byung Moo; Kim, Kunnyun

doi:10.1007/s00542-010-1139-0

Cited by 53 publications

(31 citation statements)

References 11 publications

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“…Finding coefficient of diffusion experimentally like this allows one to further predict the response of sensors with different dimensions. The absolute humidity levels were derived from the temperature and humidity data during initial and steady state condition, finding the initial concentration of water in the material, φ 0 , to be 0.8174 × 10 −6 g/mm 3 and the concentration of water at the air boundary, φ i , to be 2.792×10 −6 g/mm 3 . The thickness of the polymer was 600 nm, and the experimental time for the model was set between 0 ≤ t ≤ 200 seconds.…”

Section: Discussionmentioning

confidence: 99%

“…2 MEMS humidity sensors can be divided into categories determined by its sensing mechanism, such as capacitive, resistive, mass sensitive, thermal, or optical. Capacitive sensors have been widely used due to their good linearity, fast response time, 3 simple processing steps, 2 interface circuitry's simplicity, and low power requirements. 1 Different types of materials can be used as the dielectric RH sensing material, but they're generally either a polymer or a porous metal oxide.…”

Section: Introductionmentioning

confidence: 99%

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Gelatin as a new humidity sensing material: Characterization and limitations

2014

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The goal of this work is to assert the utility of collagen and its denatured counterpart gelatin as cost-effective alternatives to existing sensing layers comprised of polymers. Rather than producing a material that will need to be discarded or recycled, collagen, as a by-product of the meat and leather industry, could be repurposed. This work examines the feasibility of using collagen as a sensing layer. Planar electrodes were patterned with lift-off process to work with the natural characteristics of gelatin by utilizing metal vapor deposition, spin coating, and photolithography. Characterization methods have also been optimized through the creation of specialized humidity chambers that isolate specific characteristics such as response time, accuracy, and hysteresis. Collagen-based sensors are found to have a sensitivity to moisture in the range of 0.065 pF/%RH. Diffusion characteristics were also analyzed with the diffusion coefficient found to be 2.5 × 10−5 cm2/s. Absorption and desorption times were found to be 20 seconds and 8 seconds, respectively. Hysteresis present in the data is attributed to temperature cross-sensitivity. Ultimately, the utility of collagen as a dielectric sensing material is, in part, due to its fibrous macrostructures as well its hydrophilic sites along the peptide chains. Gelatin was patterned between and below interdigitated copper electrodes and tested as a relative humidity sensor. This work shows that gelatin, which is inexpensive, widely available, and easy to process, can be an effective dielectric sensing polymer for capacitive-type relative humidity sensors.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gelatin as a new humidity sensing material: Characterization and limitations

2014

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“…For these reasons, many researchers have developed capacitive-type humidity sensors with various structures. In particular, the interdigitated electrode (IDE) and the parallel plate electrode structures have been widely investigated for capacitive humidity sensors (Kang and Wise 2000;Kim et al 2010;Tetelin and Pellet 2006). The humidity sensors with the parallel plate electrode structure have more than two electrode layers (top and bottom electrodes), but the IDE structure needs only one electrode (Dai 2007;Gu et al 2004;Laconte et al 2003;Laville and Pellet 2002).…”

Section: Introductionmentioning

confidence: 99%

Capacitive humidity sensors based on a newly designed interdigitated electrode structure

2011

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This paper presents a study of capacitive humidity sensors constructed based on a newly designed interdigitated electrode (IDE) structure with a polyimide (PI) sensing layer fabricated using micro-electro-mechanical system (MEMS) technology. The humidity sensors use an IDE with increased height, formed by the surface micromachining of a silicon substrate. The fabricated sensors showed higher sensitivity in variable ambient relative humidity (RH) when compared with the humidity sensors of a conventional IDE since the horizontal electric field lines, generated between the thick electrodes, are confined to the PI sensing layer. The effect of the thickness of the PI layer was also investigated. The fabricated sensors with a 4-lm-thick PI layer showed a higher sensitivity of 37.1 fF/ %RH when compared with those of a 2-and 3-lm-thick PI layers, indicating that the properties of the sensors depend on the thickness of the PI layer. This is because the amount of the fringing electric field lines passing through the PI is determined by the PI thickness. In addition, the sensor with the 4-lm-thick PI showed very slight hysteresis with a maximum of 2.87%RH and displayed high stability with a variation range of 0.06 pF.

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“…Based on their operating principles, the existing humidity sensors can be broadly categorized into three groups: capacitive [9][10][11][12], resistive [13][14][15][16][17][18], and optical sensors [19][20][21][22][23]. Among them, the capacitive sensors are the most commonly used in the industrial and commercial fields [2] due to their high sensitivity and performance, linearity, fast response time [24][25][26], low power consumption, and good stability at higher humidity levels [12]. These sensors detect the humidity variations by changing the sensing layer dielectric when exposed to the different atmospheric humidity conditions.…”

Section: Introductionmentioning

confidence: 99%

Scalable Fabrication of Highly Flexible Porous Polymer-Based Capacitive Humidity Sensor Using Convergence Fiber Drawing

et al. 2019

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In this study, we fabricated a highly flexible fiber-based capacitive humidity sensor using a scalable convergence fiber drawing approach. The sensor’s sensing layer is made of porous polyetherimide (PEI) with its porosity produced in situ during fiber drawing, whereas its electrodes are made of copper wires. The porosity induces capillary condensation starting at a low relative humidity (RH) level (here, 70%), resulting in a significant increase in the response of the sensor at RH levels ranging from 70% to 80%. The proposed humidity sensor shows a good sensitivity of 0.39 pF/% RH in the range of 70%–80% RH, a maximum hysteresis of 9.08% RH at 70% RH, a small temperature dependence, and a good stability over a 48 h period. This work demonstrates the first fiber-based humidity sensor fabricated using convergence fiber drawing.

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High-performance capacitive humidity sensor with novel electrode and polyimide layer based on MEMS technology

Cited by 53 publications

References 11 publications

Gelatin as a new humidity sensing material: Characterization and limitations

Gelatin as a new humidity sensing material: Characterization and limitations

Capacitive humidity sensors based on a newly designed interdigitated electrode structure

Scalable Fabrication of Highly Flexible Porous Polymer-Based Capacitive Humidity Sensor Using Convergence Fiber Drawing

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