"chemically interesting but digitally useless."
Which (since El Reg is about IT) is kind of the point.
Technically it's sort of a block co-polymer (different side chains).
But yes the MS size relative to the polymer is enormous and I very strongly doubt it can do that analysis off 1 copy of the chain only. And of course it's a destructive read out process, and mfg is probably using a mod'ed version of the Merrifield protein synthesis method. Not exactly compact either.
Basically all these "chemistry/biology + storage --> super duper new storage medium" suffer from the same problem. Good (possibly very good) science but p**s poor engineering. :-(
It's only useful if the read/write package is even close to the same size, cost and speed of existing systems to the end user, and microSD is pretty small.
Non destructive read out is a good thing.
No chemical reagents needed is a good thing.
Basic physical structure unaltered by the "drive."
But engineering a "tape" (for example)a few atoms wide and a "write head" that can change the side groups on it as it moves (literally 1 bit being a few atoms) and a drive that can position the tape to that accuracy are very formidable multi-disciplinary tasks.