Self-sensing Pr-oxi-lever (piezo-resistive SiO2 cantilever) sensors for bio/chemical detection in liquid

Reported is a surface-stress sensing microcantilever with signal readout piezoresistor encapsulated by electrically insulated SiO₂ for detecting bio/chemical molecules in liquid. Specifically sensitive siloxane-based molecule monolayers or bi-layer is directly modified on the SiO₂ surface via reliable Si-O covalent bond that secures sensitivity stability and long-life working of the sensor. The sensors are successfully used for detecting 2.5% aqueous tetramethylammonium hydroxide (TMAH) and avidin at 10^-11 mol/mL trace level. An interesting phenomenon of opposite surface-stress sensing signals for different-sized target-molecules are experimentally observed by the sensor and theoretically explained.