Here's what my genius mind came up with.

First I obtained a standard D-cell battery pack that holds 2 batteries in series.

Next I installed a center tap between the two batteries in the battery pack.

So now I have a series battery pack with three terminals:

L1 is the (-) negative terminal on battery A
N is the center or neutral tap between battery A and B
L2 is the (+) positive terminal on battery B

So to prove I have 2-phase DC, I connected a dual-trace oscilloscope as follows:

The reference leads from both probes were connected to the center neutral tap.
Probe A was connected to L1
Probe B was connected to L2

As I expected, the scope showed a 1.5 volt positive phase trace and a 1.5 volt negative phase trace.

Clearly I have 3 volt 2 phase DC.

The only thing left to do is submit my paper to IEEE.