Various embodiments include heat exchangers and methods of making heat exchangers from a series of stacked plates each made of two foil sheets bonded together in bonding locations forming fluid flow passages between the foil sheets in regions where the foil sheets are not bonded. An inlet port and an outlet port located at opposite ends of the planar extent of the two foil sheets extend through the foil sheets perpendicular to the planar extent of the foil sheets. The inlet and outlet ports provide access for a first fluid to flow into or out of the internal plate passages formed between the two foil sheets. Interstitial channels are formed between the series of plates and configured to allow the flow of a second fluid between the series of plates, allowing heat to be transferred between the two fluids while isolating the two fluids from one another.