Microneedles With Improved Open Channel Cross-Sectional Geometries

A drug delivery device, comprising:

• a reservoir configured to initially retain a drug formulation;
• and
• a microneedle assembly in fluid communication with the reservoir, the microneedle assembly being configured such that a passive fluid flow of the drug formulation is directed through the microneedle assembly, the microneedle assembly including a support defining an upper surface and a lower surface, the microneedle assembly further including a plurality of microneedles extending from the lower surface, each microneedle defining an open channel for receiving the drug formulation, the open channel having a normalized hydraulic radius ranging from 0.1 to 0.8, the open channel further having a liquid-to-solid interfacial energy and a liquid-to-vapor interfacial energy when a fixed volume of the drug formulation is received therein,
• wherein the drug formulation and a cross-sectional geometry of the open channel is selected and configured such that the liquid-to-solid interfacial energy exceeds the liquid-to-vapor interfacial energy as a fluid length of the fixed volume of drug formulation is increased within the open channel.

A drug delivery device, comprising:

• a reservoir containing a liquid drug formulation;
• and
• a microneedle assembly in fluid communication with the reservoir, the microneedle assembly including a support defining an upper surface and a lower surface, the microneedle assembly further including a plurality of microneedles extending from the lower surface, each microneedle defining an open channel for receiving the drug formulation and having a skin contact area ranging from about 1,500 um2 to about 262,500 um2, the open channel having a liquid-to-solid interfacial energy and a liquid-to-vapor interfacial energy when a fixed volume of the drug formulation is received therein,
• wherein the drug formulation and a cross-sectional geometry of the open channel is selected and configured such that the liquid-to-solid interfacial energy exceeds the liquid-to-vapor interfacial energy as a fluid length of the fixed volume of drug formulation is increased within the open channel.