I would suggest getting the sculpture done as a matrix of wires, possibly
fairly open, and then driving some wires with signals, and using other wires
as detectors, a bit like a massive keyboard matrix.

I do not know how well the interaction between the driven wire and detection
wire would be with just placing a hand on it is, you may have to experiment
to find out. Get your artist friend involved in this so she has a good idea
of what is needed for the sculpture.

It may be that you will need to have some form of contact movement to get
sufficient cross coupling between the two, but I suspect that if you tried s
scheme like Hewlett Packard used in their early desktop calculators, you may
well achieve what she wants.

What HP did was to have "transformers" made of about two turns of PC track
on each winding under each key. All the windings in the X direction were
driven by a pulse, so there was 8 or 16 lines being sequentially scanned by
pulses. Windings in the Y direction were then wired in series and sufficient
pulse came out the windings for an amplifier to get a detectable pulse when
the X lines were driven. Under each key was a metal disc that became a
shorted turn on the winding when the key was pressed. A missing pulse during
a scan then represented a key press.

You may be able to do something similar by having coils of wire placed
around the sculpture, and have metal disks hanging that the public can place
against the coils. Worth a try on the bench, and the metal disk does not
have to be round - let the sculpture use her imagination on it, so long as
it will make a shorted turn on the winding.

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