In the fuel-cell stack, hydrogen goes in and electricity comes out, which then powers the car.

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The fuel cell stack, in theory, can weigh less than batteries.

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The integrated touch sensor array and solar cell stack-ups may include electrodes that are used both for collecting solar energy and for sensing on a touch sensor array.

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There's also been talk of Apple using a thinner, better panel that would likely use in-cell touch rather than stack the LCD and touch surfaces in separate layers.

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By integrating both the touch sensors and the solar cell layers into the same stack-up, surface area on the portable device may be conserved.

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But a fuel-cell engine is more than a stack of cells.

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The planar cell structure integrated a Hi-K (high capacitance) metal gate stack into the NAND production to allow for smaller floating gates and thus higher storage capacity.

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This stack inside a flow battery, where the electrolyte meets the electrodes, looks a lot like a fuel cell.

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