Patterned, swellable hydrogels are finding increasing applications as sensing, optical focussing and actuation elements in Lab-on-a-chip structures because of their property that they undergo large changes in dimension in response to changes in external environment. Often a goal when developing these materials and fabrication methods is to improve their temporal response whilst maintaining the maximal volume changes needed for the device to be effective. Using laboratory based methods it is difficult to determine how far water and salt penetrate into these structured hydrogels as they swell: the easier it is for water to get into the core of the gel pattern, the faster it will swell. Thus, in this novel NR experiment, we seek to use off-specular NR to evaluate the lateral distribution of water and salt in unswollen and swollen lithographically fabricated arrays of hydrogel pillars.