title: Microresonator mass sensors for detection of Bacillus anthracis Sterne spores in air and water.
abstract: Towards the goal of developing a real-time monitoring device for microorganisms, we demonstrate the use of microcantilevers as resonant mass sensors for detection of Bacillus anthracis Sterne spores in air and liquid. The detection scheme was based on measuring resonant frequency decrease driven by thermally induced oscillations, as a result of the added mass of the spores with the use of a laser Doppler vibrometer (LDV). Viscous effects were investigated by comparing measurements in air and deionized (DI) water along with theoretical values. Moreover, biological experiments were performed which involved suspending spores onto the cantilevers and performing mass detection in air and water. For detection of spores in water, the cantilevers were functionalized with antibodies in order to fix the spores onto the surface. We demonstrate that as few as 50 spores on the cantilever can be detected in water using the thermal noise as excitation source. Measurement sensitivity of 9.23 Hz/fg for air and 0.1 Hz/fg for water were obtained. These measurements were compared with theoretical values and sources of improvement in cantilever sensitivity in a viscous medium were also discussed. It is expected that by driving the cantilevers and using higher order modes, detection of a single spore in liquids should be achievable.
authors.affiliation: Laboratory of Integrated Biomedical Micro/Nanotechnology and Applications, Birck Nanotechnology Center, Bindley Biosciences Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, United States.
authors.forename: Angelica P
authors.initials: AP
authors.lastname: Davila
authors.forename: Jaesung
authors.initials: J
authors.lastname: Jang
authors.forename: Amit K
authors.initials: AK
authors.lastname: Gupta
authors.forename: Tom
authors.initials: T
authors.lastname: Walter
authors.forename: Arthur
authors.initials: A
authors.lastname: Aronson
authors.forename: Rashid
authors.initials: R
authors.lastname: Bashir
mesh_terms: D000391:Air Microbiology; D001408:Bacillus anthracis / Q000302:isolation & purification*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D013171:Spores, Bacterial; D014871:Water Microbiology