What type of adhesive requires adhesive on only one side?

The correct choice is non-contact adhesive. This type of adhesive is designed to bond surfaces together with adhesive applied to only one side. This feature can be particularly useful in applications where surfaces need to be joined without the risk of adhesive bleed-through or where the second surface may not be compatible with adhesive application. Non-contact adhesives often rely on specific bonding mechanisms, such as pressure to form a bond or the application of heat or activation upon contact.

In contrast, contact adhesives require adhesive on both surfaces to be effective; they bond upon immediate contact once the two surfaces are pressed together. Foam adhesives may have unique foam structures but do not specifically refer to the requirement for adhesive on one side. Thermal adhesives typically need a heat source to activate or cure, and they also may require application on multiple surfaces for effective bonding. Therefore, non-contact adhesive stands out due to its unique one-sided application characteristic.