A sample holder includes sample carrier and sealing foil thermally sealing microfluidic sample carrier cavities. The sealing foil has a sealing layer connected with the sample carrier. Sealing layer softening temperature is near sealing temperature of the sealing layer during sealing. The sealing foil outer layer use temperature is greater than sealing heating temperature and greater than or equal to sealing temperature. The sealing foil includes a height equalizing layer having softening temperature below sealing heating temperature. The equalizing layer is ductile at temperature less than or equal to sealing heating temperature and greater than or equal to sealing temperature. A sealing foil decoupler layer, at layer temperature less than or equal to sealing heating temperature or greater than or equal to sealing temperature, is stiffer than the equalizing and sealing layers. The equalizing layer is between outer and decoupler layers and sealing layer is outwardly of decoupler layer.