The present invention relates to a microfluidic device, comprising a laminate of first and second films, one or each film including an integrally thermoformed structure such that the films together define an enclosed volume (19) for fluid containment therebetween, characterised in that each film itself comprises a laminate of a relatively higher softening temperature thermoplastic polymeric material (14,17) and with respect thereto, a relatively lower melt temperature thermoplastic polymeric material (15,16), the respective relatively low melt temperature thermoplastic polymeric materials of each film being melted together to attach the said first and second films together. The invention further relates to a method of manufacturing the microfluidic device.