Articles enabled by an injection molding process that molds parts on a carrier web located between mold halves and uses ultrasonic energy to assist flow of polymer melt into the mold cavity. One such article is a carrier web having a high density of molded parts, i.e., bearing an array of molded articles adhered to the web in rows and columns, the articles being spaced closer (center-to-center or edge-to-edge) than the diagonal spacing between articles in the next adjacent row and next adjacent column. Another such article is a microneedle array on a land no more than 250 μm thick on which at least 60% of the microneedles across the array are filled (i.e., completely formed).