Fabrication, calibration, and preliminary testing of microcantilever‐based piezoresistive sensor for BioMEMS applications

Abstract

In this study, the authors demonstrate the fabrication, calibration, and testing of a piezoresistive microcantileverbased sensor for biomedical microelectromechanical system (BioMEMS) application. To use any sensor in BioMEMS application requires surface modification to capture the targeted biomolecules. The surface alteration comprises self-assembled monolayer (SAM) formation on gold (Au)/chromium (Cr) thin films. So, the Au/Cr coating is essential for most of the BioMEMS applications. The fabricated sensor uses the piezoresistive technique to capture the targeted biomolecules with the SAM/Au/Cr layer on top of the silicon dioxide layer. The stiffness (k) of the cantilever-based biosensor is a crucial design parameter for the low-pressure range and also influence the sensitivity of the microelectromechanical system-based sensor. Based on the calibration data, the average stiffness of the fabricated microcantilever with and without Au/Cr thin film is 141.39 and 70.53 mN/m, respectively, which is well below the maximum preferred range of stiffness for BioMEMS applications. The fabricated sensor is ultra-sensitive and selective towards Hg 2+ ions in the presence of other heavy metal ions (HMIs) and good enough to achieve a lower limit of detection 0.75 ng/ml (3.73 pM/ml).

Ultrasensitive detection of cadmium ions using a microcantilever-based piezoresistive sensor for groundwater

“…At a flow of 30 μL/min, the total injected volume is 0.69 mL for a maximum of 23 min. Therefore, the corresponding mass of AlCl 3 , MnCl 2 , CrCl 3 , CdCl 2 , PbCl 2 , and HgCl 2 is 0.67 ng, 0.55 ng, 0.74 ng, 0.56 ng, 0.77 ng, and 0.75 ng, respectively (refer to [40,52] for LOD calculation). Table 1, it is clear that the proposed microfluidic platform has the ability to selectively capture Cd(II) at amounts as small as 2.78 pM/mL (LOD) and outperforms other approaches, which require sophisticated measuring instruments.…”

“…At a flow of 30 μL/min, the total injected volume is 0.69 mL for a maximum of 23 min. Therefore, the corresponding mass of AlCl 3 , MnCl 2 , CrCl 3 , CdCl 2 , PbCl 2 , and HgCl 2 is 0.67 ng, 0.55 ng, 0.74 ng, 0.56 ng, 0.77 ng, and 0.75 ng, respectively (refer to [ 40 , 52 ] for LOD calculation).…”

“…We have previously investigated SAMs of homocysteine (HCys) and pyridinedicarboxylic acid (PDCA) for the selective sensing of Hg(II) ions using a portable piezoresistive platform [39,40]. Experimental results confirmed that proposed setup is capable of sensing in the picomolar range.…”

“…Previously, a polysilicon-based piezoresistive sensor was fabricated using a standard microfabrication process. It was calibrated using atomic force microscopy (AFM) [40]. The process begins with thermal oxidation of Si at 1000 °C using an oxidation furnace to obtain a thermally grown SiO 2 layer followed by masking and etching to get the desired pattern.…”

“…The polysilicon is deposited in a low-pressure chemical vapor deposition (LPCVD) furnace at 630 °C and boron doping (10 18 per cm 3 ) is carried out using ion implantation at 35 keV. The upper SiO 2 layer is formed by re-oxidizing the polysilicon in an oxidation furnace [40]. The stiffness (k) of the fabricated piezoresistive sensor measured using AFM is 131-146 mN/m, which is well below the stiffness required for BioMEMS applications (1000 mN/m [41,42]).…”