Hybrid Micro Electro Mechanical Sensor Based on Graphene Oxide/Polyvinyl Alcohol for Humidity Measurements

Abstract

In this paper, we present a redundant micromachined sensor based on Bulk and Etch. Silicon-on-Insulator (BESOI) process for measurements of relative humidity (RH) by using Graphene-Oxide/Polyvinyl-Alcohol (GO/PVA) composite. The microsensor is a mechanical oscillator composed of a proof mass with multilayer of nanomaterials (GO/PVA) and suspended by four crab leg springs. The realized redundant approach concerns the possibility to use different readout strategies in order to estimate the same measurand: RH. This is an intriguing solution to realize a “robust measurement system”, with multiple outputs by using the GO/PVA as functional material. In presence of RH variation: (1) it changes its mass and; as consequence; a variation of the natural frequency of the oscillator can be observed in the frequency domain; (2) it also varies the conductivity which can be measured by using two integrated electrodes. The sensor has been designed; studied; modeled and experimental results demonstrate the effectiveness of our implementation.

Cantilever-Based Sensor Utilizing a Diffractive Optical Element with High Sensitivity to Relative Humidity

“…Humidity was selected as water vapors are non-toxic, and the temperature and relative humidity controlled environments are readily available. Table S1 compares the achieved limit of detection of the relative humidity of the proposed sensor platform (0.1% RH) to other relevant sensor technologies, such as microcantilevers (1.8% RH) [ 32 ], flat holographic sensors (1% RH) [ 39 , 47 , 48 ] and optical fiber sensors (0.12% RH) [ 56 ] previously reported in the literature.…”

“…The comparison reveals the high potential of this novel optomechanical sensor. In addition to the high sensitivity, when the low electronics complexity and cost, the low susceptibility to interference from electromagnetic fields, the low– to -medium manufacturing complexity, and the low cost of the sensor transducer are considered, it is clear that this novel sensor technology [ 57 ] is compared favorably with optical fiber Bragg grating sensors [ 16 , 35 , 58 , 59 , 60 ] plasmonics/nanoplasmonics sensors [ 33 ] and MEMS/NEMS sensors [ 14 , 16 , 30 , 31 , 32 , 33 , 34 , 35 ] and its further development is well justified.…”

“…A large humidity range (35–95%) was tested, and the sensor showed a linear detection response, but its sensitivity was rather low [ 31 ]. A MEMS mechanical oscillator has been used to measure RH by correlating the change in mass of multilayers of nanomaterials on the oscillator to changes in RH, a resolution of ~1.8% RH being obtained across a range of 0 to 80% RH [ 32 ]. Silicon microcantilevers coated with graphene oxide as the sensing layer have also been tested to detect humidity between 10 and 90% RH, but changes in the sensitivity measured in different RH ranges were observed.…”

Investigation on the Role of Ionic Liquids in the Output Signal Produced by Bacterial Cellulose-Based Mechanoelectrical Transducers

“…Cantilever sensing systems can be used at their mechanical resonant frequency when a signal of the maximum level can be obtained [ 36 , 52 , 53 , 54 ].…”

Analysis of a Hybrid Micro-Electro-Mechanical Sensor Based on Graphene Oxide/Polyvinyl Alcohol for Humidity Measurements

“…Water molecules are accommodated within the GO interlayers, hence the resistive property changes. By selecting the right thickness, a continuous change in resistance and capacitance with respect to humidity covering a large range, i.e., 20% to 80% RH, has been realized [20].…”