Ultrasonic transdermal system for withdrawing fluid from an organism and determining the concentration of a substance in the fluid

Abstract

A noninvasive method and apparatus for withdrawing fluid from an organism and determining the concentration of a substance in the fluid is disclosed. The noninvasive apparatus comprises a substance concentration sensor (120) that includes an extraction transducer (126) and a substance sensing transducer (133). The extraction transducer includes a container (123); a planar piezoelectric (ultrasonic) transducer (124); a focusing lens (125); and a backing layer (127). The container includes a flange (129) that is attached to the skin of an organism by an adhesive film seal (131). The focusing lens (125) is a plano-concave shape such that the concave side faces the skin of the organism. Thus, the focusing lens (125) defines a cavity (135). Located in the cavity (135) is the substance sensing transducer (133). Positioned above the focusing lens is the ultrasonic transducer (124). A pulse generator (121) is connected to and drives the ultrasonic transducer. A test data processor (122) is connected to the substance sensing transducer (133). Ultrasonic transducer pulses are focused by the focusing lens (125) into the organism, traumatizing the skin underlying the cavity (135). The trauma causes the dermal-epidermal junction membrane and the capillary endothelial joints to open and allow fluid to be drawn from the cavity (135). The substance to be detected in the fluid is sensed by the substance sensing transducer (133) causing the output of the transducer to change. The output changes are analyzed by the test data processor (122).