The invention relates to a pagewidth printhead assembly. The assembly includes a molded polymer ink manifold defining a plurality of discrete fluid conduits therethrough. The assembly also includes a plurality of printhead integrated circuits (ICs) each having a plurality of micro-electromechanical nozzle arrangements for operatively ejecting printing fluid onto a printing medium. Each IC defines a plurality of discrete supply channels for supplying the nozzle arrangements with fluid, and has a bonding surface with a plurality of trenches etched therein, the trenches having a width of less than 10 microns to operatively attract a liquid adhesive by capillary action. The assembly also includes a thermosetting sealing film having a heat liquefied adhesive layer to adhere the bonding surface of the ICs to the lower member when said film is heated, so that the conduits and supply channels are in fluid communication with each other.