Microneedle arrays for biosensing and drug delivery

A method for in situ measurement of one or more target chemical species present in a physiological fluid, the method comprising:

• applying a stimulus signal to an electrically conductive structure disposed on a substrate, wherein the electrically conductive structure is disposed in a spatially-defined region separate from an array of protrusions attached to and extending from an anterior surface of the substrate, each protrusion possessing a vertical extent of between 20 and 1500 micrometers from said substrate to a distal extent of each protrusion, and
• reading a resultant signal arising at an interface between the physiological fluid and an electrically-conducting probe disposed in a defined exposed region on each protrusion by providing an isolated electrical communication with said probe using a spatially-defined conducting channel in contact with the probe and the electrically conductive structure located in the spatially-defined region separate from said protrusion,
• wherein a property of said resultant signal is indicative of a concentration of the one or more target chemical species present in said physiological fluid.