Atomic force microscope based biomolecular force-clamp measurements using a micromachined electrostatic actuator

Abstract

The authors describe a method for biomolecular force clamp measurements using atomic force microscope (AFM) cantilevers and micromachined membrane-based electrostatic actuators. The actuators comprise of Parylene membranes with embedded side actuation electrodes and are fabricated on a silicon substrate. The devices have a displacement range of 1.8 μm with 200 V actuation voltage, and displacement uncertainty is 0.8 nm, including the noise and drift. The settling time, limited by the particular amplifier is 5 ms, with an inherent range down to 20 μs. A force clamp measurement setup using these actuators in a feedback loop has been used to measure bond life-times between human IgG and anti-human IgG molecules to demonstrate the feasibility of this method for biological experiments. The experimental findings are compared with a molecular pulling experiment and the results are found to be in good agreement.

Frequency-dependent nanomechanical profiling for medical diagnosis

“…A schematic for a proposed enhancement to this type of device is shown in Figure 2. In addition to optical imaging, the device could be equipped with one or more piezoelectrically excited membranes coupled with a sensing mechanism, such as an AFM cantilever or other type of mechanical sensor (similar stand-alone developments already exist [31,32]). The mechanical response of the membrane could be measured while it is in close contact with the surrounding tissue.…”

“…In contrast, as the length scale of the probe decreases, the mechanical information obtained is restricted to thinner and thinner regions near the sample surface. [30] that perform optical imaging, whose capabilities could be augmented to perform mechanical sensing, for example, through the incorporation of a piezoelectrically actuated membrane equipped with a mechanical response sensing mechanism [31,32].…”

“…Figure 2: Schematic of proposed enhanced endoscopy pill. The design is based on existing devices[30] that perform optical imaging, whose capabilities could be augmented to perform mechanical sensing, for example, through the incorporation of a piezoelectrically actuated membrane equipped with a mechanical response sensing mechanism[31,32].…”