Microneedle array assembly, drug delivery device and method for administering liquid across a broad area at low pressure

Abstract

A uniformity control membrane can be securely engaged against an upstream side of a microneedle array and configured so that resistance to flow through the uniformity control membrane is substantially greater than the resistance to flow through the microneedle array. These differences in flow resistance can facilitate uniform administration of a liquid formulation into the patient's skin across a broad area and at a relatively low pressure, such as by way of capillary action. The administration of the liquid formulation into the patient's skin across the broad area can result from the liquid formulation being administered by way of at least a majority of the microneedles of the microneedle array.

We claim: 
     
         1 . A microneedle array assembly, comprising:
 a microneedle array comprising   a base having opposite upstream and downstream sides and defining a plurality of apertures extending between the upstream and downstream sides; and   a plurality of microneedles extending from the downstream side;   wherein each of the plurality of apertures are defined in the base proximate each of the plurality of microneedles, and   wherein the resistance to flow through the upstream side of the base is at least about 30 times greater than resistance to flow through the microneedle array, wherein the at least about 30 times greater is a difference in the resistance to flow between the upstream side and the downstream side of the base.   
     
     
         2 . The microneedle array assembly of  claim 1 , wherein each aperture of the plurality of apertures comprises a pair of downstream openings proximate one or more exterior channels extending along each microneedle of the plurality of microneedles. 
     
     
         3 . The microneedle array assembly of  claim 1 , wherein each aperture of the plurality of apertures extends through each microneedle of the plurality of microneedles to form an interior channel through an interior of each microneedle of the plurality of microneedles. 
     
     
         4 . The microneedle array assembly of  claim 3 , wherein each aperture of the plurality of apertures is positioned coaxial to each interior channel of each microneedle of the plurality of microneedles. 
     
     
         5 . The microneedle array assembly of  claim 1 , further comprising at least one membrane engaged against the upstream side of the base. 
     
     
         6 . The microneedle array assembly of  claim 5 , wherein the resistance to flow through the at least one membrane is within a range of from about 30 times to about 100 times the resistance to flow through the microneedle array. 
     
     
         7 . The microneedle array assembly of  claim 5 , wherein the resistance to flow through the at least one membrane is at least about 40 times greater than the resistance to flow through the microneedle array. 
     
     
         8 . The microneedle array assembly of  claim 7 , wherein the resistance to flow through the at least one membrane is within a range of from about 40 times to about 100 times the resistance to flow through the microneedle array. 
     
     
         9 . The microneedle array assembly of  claim 5 , wherein the resistance to flow through the at least one membrane is at least about 50 times greater than the resistance to flow through the microneedle array. 
     
     
         10 . The microneedle array assembly of  claim 5 , wherein the resistance to flow through the at least one membrane is within a range of from about 50 times to about 100 times the resistance to flow through the microneedle array. 
     
     
         11 . The microneedle array assembly of  claim 5 , wherein the at least one membrane has a relatively smooth side and a relatively rough side, and the at least one membrane being engaged against the upstream side of the base is comprised of the smooth side of the at least one membrane being engaged against the upstream side of the base. 
     
     
         12 . The microneedle array assembly of  claim 5 , wherein the at least one membrane is a track etched membrane. 
     
     
         13 . A drug delivery device, comprising:
 a microneedle array assembly according to  claim 5 ; and   a reservoir operatively associated with the microneedle array for supplying liquid to the microneedle array by way of the at least one membrane.   
     
     
         14 . The drug delivery device of  claim 13 , further comprising a force provider for causing at least some of the liquid to flow from the reservoir toward the microneedle array assembly. 
     
     
         15 . The drug delivery device of  claim 14 , wherein:
 the force provider is for causing an increase in pressure of the liquid;   the at least one membrane is for causing a decrease in pressure of the liquid;   and   an absolute value of the increase in pressure is approximately equal to an absolute value of the decrease in pressure.   
     
     
         16 . The drug delivery device of  claim 14 , further comprising a plenum in fluid communication with an upstream side of the plenum, wherein the force provider is for causing at least some of the liquid to flow from the reservoir to the plenum. 
     
     
         17 . The drug delivery device of  claim 16 , further comprising a cannula in fluid communication with the plenum, wherein the drug delivery device is configured so that, in use, the liquid passes from the reservoir through the cannula into the plenum before passing through the at least one membrane and out of the microneedle array.