Techniques are described for facilitating interactions between computing systems, such as by performing transactions between parties that are automatically authorized via a third-party transaction authorization system. The topsheet has an inner surface oriented toward the interior of the absorbent article and an outer surface oriented toward the skin and hair of the wearer when the absorbent article is being worn and an absorbent core positioned between the topsheet and the backsheet. The top part and the bottom part comprises radiating waveguides coupled electromagnetically by way of coupling slots to a feed waveguide.