Separation of bacterial spores from flowing water in macro-scale cavities by ultrasonic standing waves

The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of 40-250 ml/min has been achieved with 15% efficiency in a single pass at 40 ml/min.Comment: 11 pages, 6 figure

HIGH EFFICIENCY PARTICLE COLLECTION MEMBRANES WITH HIGH AIR AND MOISTURE PERMEABILITY: CHARACTERIZATION, MODELING AND LARGE-AREA DEPOSITION HIGH EFFICIENCY PARTICLE COLLECTION MEMBRANES WITH HIGH AIR AND MOISTURE PERMEABILITY: CHARACTERIZATION, MODELING A

ABSTRACT Physical Sciences Inc. (PSI) has developed, characterized and modeled the performance of nonwoven membranes for percutaneous protection. The membranes, composed of polymer fibers deposited by electrospinning, collect particles and aerosols over the size range of 0.2-1.0 micrometers with high efficiencies while maintaining the high air and moisture permeabilities required for wearer comfort. The membranes' high surface-to-volume ratio also provides a platform for the inclusion of reactive species for self-detoxification functionality. PSI has developed a prototype system for covering large substrate areas. For membranes with mean fiber diameters between 700 and 850 nm, a filtration efficiency of 98% was found at an areal density of 2.9 mg/cm 2 for 0.3 µm diameter particles. Membranes with areal densities up to 1.5 mg/cm 2 were found to have low water vapor diffusion resistances of about 1 sec/m, indicating that the coatings can be spun onto conventional fabrics and provide protection while retaining high breathability