Jessica Arlett (Graduate Student)
Benjamin Gudlewski (Research Staff Member)
James Maloney (Graduate Student)
Martha-Helene Stapleton (Undergraduate Student)
Hongxing Tang (Staff Scientist)
Darron Young (Staff Scientist)

The capability of cantilevers to detect the force of chemical interactions has been amply demonstrated by researchers performing chemical force microscopy (CFM) using modified AFM instruments.  Although the devices are large and complex, CFM shows the feasibility of detecting the presence and amount of a given chemical species by their interactions with a microfabricated device.  We are attempting to extend the advances of CFM in several key fashions to create a BioNEMS assay approaching the stochastic limit, employing a novel detection scheme and miniaturizing the active volume to sizes relevant to single cells. 

Our aim is to study the motion of the NEMS cantilevers to follow binding and unbinding events.  A cantilever that is not coupled at its tip by a receptor-ligand pair will fluctuate in its position more dramatically than a cantilever that is restricted by a ligand-receptor pair.  Strong ligand-receptor bonds can partially arrest the cantilever motion for considerable time; even weak interactions will alter the statistics of cantilever motion..


The fluid-based mechanical force detection is implemented as a piezoresistive strain transducer on a Si cantilever. The transducer converts the motion of the cantilever into an electrical signal, in this case via  the strain-induced change in resistance of a conducting path patterned from p+ doped Si epilayer on the top surface of the cantilever .  The coupled sensitivity we expect to achieve, as low as ~8fN/Hz1/2 limited predominantly by the fluidic fluctuations, opens exciting new potential for single molecule sensing with wide bandwidths ~MHz, and at correspondingly fast time scales. Additionally, the high level of dimensional control available through the nanofabrication technique offers immense potential for patterning arrays of such cantilevers within very small volumes.  Large scale integration of BioNEMS offers the possibility of sensing many different types of molecules simultaneously in the fashion of existing “bioarray” technology, or of using sensor redundancy to enhance detection of a particular analyte in the extremely dilute limit 



    Scott Fraser (Professor, Caltech)
    Rusty Lansford(Staff Scientist, Caltech)
    Jay Nadeau (Jet Propulsion Laboratory)
    Alan Pinkney (Staff, Caltech)

    Mike Cross (Professor, Caltech)
    Mark Paul (Visiting Associate, Caltech)
    Rob Phillips (Professor, Caltech)
    Raul Radovitzky (MIT)
    Darren Segall (Postdoctoral Scholar, Caltech)
    Jerry Solomon (Professor, Caltech)