Integrated silicon field-effect sensors and microfluidics for biomolecular detection

Abstract

Microfabricated silicon field-effect sensors with integrated poly(dimethylsiloxane) microfluidic channels have been demonstrated. These devices are designed for the label-free detection and recognition of specific biomolecules such as DNA. Label-free methods eliminate the time-consuming and costly step of tagging molecules with radioactive or fluorescent markers prior to detection. The devices presented here are sensitive to the intrinsic charge of the target molecules, which modulates the width of the carrier-depleted region of a lightly-doped silicon sensor. The variable depletion capacitance is precisely measured, indicating changes in sensor surface potential of less than 30[micro]V. The integrated microfluidic channels enable the delivery of small (nanoliter-scale) amounts of fluid directly to the sensors. Capacitance-voltage curves were recorded using phosphate buffered saline (PBS) as the test electrolyte; a maximum slope of 44pF/V was measured in depletion. pH sensitivity was also demonstrated using modified PBS solutions. A device with dual 80x80Om sensors yielded a response of 40mV/decade, referenced to the fluid electrode. A device with dual 50x50[micro]m sensors yielded a response of 12mV/decade, referenced to the sensors.