The invention relates to a method for making a diagnostic element. The method comprises providing a shaped channel comprising at least one holding port and an inlet passage and outlet passage on either side of the holding port; flowing in a diagnostic gel into the inlet passage of the shaped channel; and encapsulating the diagnostic gel in the at least one holding port to form a diagnostic element. The invention also provides a method for using a diagnostic element, wherein the method comprises flowing sample through the diagnostic gel to provide an analyte diagnostic gel; analyzing the analyte diagnostic gel.