Low-stress transfer bonding using floatation

A novel method for transferring thin, large-area polymer layers from a mould and its subsequent bonding to a destination substrate is presented here. Buoyancy is used for transfer via floatation to allow the release of internal stress in the polymer and to avoid induced strain. Additionally, floatation leads to wrinkle-free contact between the polymer layer and its destination substrate, an important feature for the transfer of large-area polymer sheets. Poly(vinyl alcohol) is used as a release film on the mould, from which the device polymer layer is released using ultrasonication. The polymer layer floats from the mould to a destination surface, to which it automatically aligns. Here, the method is demonstrated by the successful manufacturing of a 4′′ sized, triple microfluidic layer PDMS stack on a silicon wafer, containing a total of 48 large-area, fragile membranes, each with a thickness of 50 μm. (Some figures may appear in colour only in the online journal)