Active microcantilever device for biological agent detection

The measurement of binding forces between specific antigen-antibody pairs presents a powerful tool for sensitive detection with applications in medical diagnostics, bioagent sensing, and environmental monitoring. The ability to detect single molecular binding events with an AFM, using the technique of dynamic force spectroscopy, is a known capability; however, reliance on traditional AFM architectures limits the use of this method to laboratory environments. The approach presented here uses active piezoelectric microcantilevers, providing electronic output for detection of molecular binding. Functionalization of this device with specific antibodies provides a platform for a stand-alone detection device. As the microcantilever can be operated as both a sensor and an actuator, the detection scheme includes actuating the cantilever to present an antibody bound to the cantilever tip to a second antibody bound to a fixed substrate. If a target antigen is present in solution, the cantilever detects the mechanical strain and vibrational response created by the binding force and subsequent rupture of the antigen-antibody pair. This detection strategy distinguishes this work from resonance-based cantilever devices that respond to changes in cantilever mass based on adsorption of numerous antigen molecules. In this research, piezoelectric microcantilevers were fabricated, and initial results were obtained demonstrating transient response caused by rupture of nonspecific adhesion forces in air and water environments. Analytical results are also presented relating geometrical parameters with sensor performance.