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Using infrared imaging and atomic force microscopy enhances surface analysis of hydrophilic heat-seal films. Herbert M. Hand Sr., Peter Gabriele, and David M. Schaefer Tapes with inherently good surface-wetting characteristics are needed to aid in the wicking of blood, serum, sputum, and other biological fluids in diagnostic test strips. These single- and double-faced hydrophilic adhesives and coated-tape products play an important role as components in in vitro diagnostic biosensors. For example, they are used as support components in lateral-flow devices by joining membrane and conjugate pads with a rigid, low-energy substrate. The hydrophilicity of these tapes reduces the surface tension of biological fluids, allowing rapid transfer from an inlet area to a remote reagent area. In capillary designs, the tapes are often used as roof components, with the hydrophilic side facing into the channel. As double-faced constructions, hydrophilic tapes are used to create high-energy channels between cover and base components. Hydrophilic pressure-sensitive adhesives and heat-seal adhesives offer the added benefit of bonding to a variety of low-surface-energy substrates, thereby providing a seal to maintain a constant-volume sample area. To meet the growing needs of IVD manufacturers, proprietary hydrophilic adhesives are being made by matching polymer resin chemistries and surfactants, resulting in a dual bonding-and-wetting quality. Unlike hydrogel coatings and other coatings with interpenetration polymer networks that exhibit bulk hydrophilic properties, these proprietary hydrophilic adhesives contain active surfaces that reduce tension in aqueous fluids at the surface. The result is ease of wetting, thus allowing for rapid transport of biological fluids across a surface (see Figure 1). This property overcomes the need for surface modifications, such as corona treatment, acid etch, or anodization, that are subject to time-related stability issues and higher costs due to complex production processes. This article examines the surface behavior of hydrophilic adhesives formulated using polymer resins and