Looking at the Chinese Room thought experiment from Philosophy 101 we can surmise there's more to consciousness than just electrical activity. Some scientists think there's a quantum element to it. Still that doesn't necessarily mean it's tied to organic processes per se. I feel that true sentience is going to be possible for a machine; further, I believe that everything that's no impossible is inevitable.

Better hope our robot overloads are wiser and more benevolent than their erstwhile human masters! grin
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“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman