NCJ Number
227500
Date Published
2009
Length
70 pages
Annotation
This report describes the development of an automated method for high efficiency, high purity separations of male and female DNA in the analysis of sexual assault evidence, using acoustic trapping (Acoustic Differential Extraction).
Abstract
The acoustic trapping microdevice consists of piezoceramic microtransducers embedded in a printed circuit board layer, which serves as the bottom of a microchannel, and a glass fluidic layer that contains the microchannel structure. Upon the application of an alternating voltage to the microtransducers, a standing ultrasonic acoustic wave is formed within the microchannel, generating pressure minima in the center. Particle and cells, in a size- and density-dependent manner, are drawn to these minima by acoustic forces generated from the standing wave. The magnitude and direction of the force are dictated by the physical characteristics of the specific particles or cells. The Acoustic Differential Extraction (ADE) system has been optimized to immobilize sperm cells while free DNA (primarily from epithelial cell lysate) will not be trapped. A biological sample that contains a mixture of sperm and epithelial cell lysate is infused through the microfluidic channels and transported over the transducers. Upon activation of the ultrasound, sperm cells are retained in the acoustic trap while free DNA is directed toward the female DNA outlet. Laminar flow valving is used to redirect the flow toward the male outlet, and the ultrasound is terminated, resulting in the release of sperm cells from the acoustic trap and the subsequent movement of cells toward the male outlet. The male and female products from the ADE system were collected from their respective outlets and analyzed off-chip. DNA purification, amplification, and separation were performed using conventional laboratory methods. 19 figures and 58 references
Date Published: January 1, 2009