coatings to enhance the echogenicity of materials are especially useful for medical devices wherein the practitioner desires to locate or visualize a device by ultrasonic imaging when the device is inserted into a body cavity . these coatings can be applied to any device of virtually any composition . to accomplish this , a polymer matrix is formed containing an entrapped gas in enclosed bubbles or open surface channels or cavities . coated needles are visible in ultrasound when inserted in animals . a pre - coat or base coat may be applied to condition the surface to enhance adhesion . a finish coat or top coat may be applied to improve durability , smoothness , and biocompatibility , lubricity , antibiotic , antimicrobial , antithrombogenic activity , and other desirable properties for the finished product . coating liquids and methods for preparing and applying such coatings are disclosed , including forming bubbles by chemical reaction during the coating process .