  We study a new mechanism of active matter confinement of a thin, active
nematic sample consisting of microtubules, activated by Adenosine Triphosphate
(ATP), placed between a slab of passive liquid crystal, the compound 8CB, and
water. The 8CB slab is kept at a temperature below the phase transition value
between the nematic and the smectic A phases. The smectic A molecules are
horizontally aligned with an applied magnetic field, with their centers of mass
arranged on equally spaced layers perpendicular to the field. The contact with
the active nematic prompts flow in the smectic slab, along the direction
parallel to the layers. This flow direction is transferred back to the active
nematic. We set up a model of such contact flow and make predictions on the
experimentally observed pattern, from the point of view of asymptotic, linear
and nonlinear analyses. We examine such results within the scope of the
principle of minimum energy dissipation of the flow. For analytic convenience,
we consider the active nematic confined between two symmetric 8CB slabs, and
show that the conclusions still hold when replacing the bottom smectic A
substrate with water, as in the experimental setting.
