Polymer nanocomposite nanomechanical cantilever sensors: material characterization, device development and application in explosive vapour detection

Abstract

This paper reports an optimized and highly sensitive piezoresistive SU-8 nanocomposite microcantilever sensor and its application for detection of explosives in vapour phase. The optimization has been in improving its electrical, mechanical and transduction characteristics. We have achieved a better dispersion of carbon black (CB) in the SU-8/CB nanocomposite piezoresistor and arrived at an optimal range of 8-9 vol% CB concentration by performing a systematic mechanical and electrical characterization of polymer nanocomposites. Mechanical characterization of SU-8/CB nanocomposite thin films was performed using the nanoindentation technique with an appropriate substrate effect analysis. Piezoresistive microcantilevers having an optimum carbon black concentration were fabricated using a design aimed at surface stress measurements with reduced fabrication process complexity. The optimal range of 8-9 vol% CB concentration has resulted in an improved sensitivity, low device variability and low noise level. The resonant frequency and spring constant of the microcantilever were found to be 22 kHz and 0.4 N m(-1) respectively. The devices exhibited a surface stress sensitivity of 7.6 ppm (mN m(-1))(-1) and the noise characterization results support their suitability for biochemical sensing applications. This paper also reports the ability of the sensor in detecting TNT vapour concentration down to less than six parts per billion with a sensitivity of 1 mV/ppb.

Evaluation of Effective Elastic, Piezoelectric, and Dielectric Properties of SU8/ZnO Nanocomposite for Vertically Integrated Nanogenerators Using Finite Element Method

“…The matrix, SU8, is a negative photoresist, commonly employed in microfabrication, and nanocomposites with SU8 as matrix have been used to fabricate structural components of MEMS sensors [48][49][50][51][52]. The mechanical properties of this polymer depend on the processing conditions.…”

Polymer MEMS Sensors

“…Hence, SU-8 microcantilevers with integrated piezoresistor made of nanocomposite of SU-8 and Carbon Black have been developed. [23,[25][26][27]. In such a device, the strain in the microcantilever is measured by the change in resistance of the embedded piezoresistive layer containing conducting nanoparticles.…”

“…Th e samples were prepared with diff erent sonication energies for DLS analysis and the size distributions of CB nanoparticles in these diff erent samples were analyzed. Based on these analysis sonication energy of 3 kJ was adopted for preparation of SU-8/CB nanocomposite [27]. Similar to SU-8, SU-8/CB nanocomposite were patterned using standard photolithograhy process with an increased UV dose.…”

“…Th e performance of SU-8 based polymer nanomechanical sensors could be enhanced by incorporating ultra-sensitive electrical transduction schemes that are compatible with SU-8 processing [23][24][25][26][27][28][29][30][31][32]. Design and development of SU-8 microcantilever sensors with four novel electrical transduction schemes namely (1) polymer nanocomposite piezoresistive microcantilever sensors [25][26][27] (2) Organic CantiFET [28] (3) AZO CantiFET [29] and (4) polymer nanocomposite piezoelectric microcantilever sensors [30][31][32] are discussed here.…”

“…Design and development of SU-8 microcantilever sensors with four novel electrical transduction schemes namely (1) polymer nanocomposite piezoresistive microcantilever sensors [25][26][27] (2) Organic CantiFET [28] (3) AZO CantiFET [29] and (4) polymer nanocomposite piezoelectric microcantilever sensors [30][31][32] are discussed here.…”