  We demonstrate theoretically that acoustic forces acting on inhomogeneous
fluids can be used to pattern and manipulate solute concentration fields into
spatio-temporally controllable configurations stabilized against gravity. A
theoretical framework describing the dynamics of concentration fields that
weakly perturb the fluid density and speed of sound is presented and applied to
study manipulation of concentration fields in rectangular-channel acoustic
eigenmodes and in Bessel-function acoustic vortices. In the first example,
methods to obtain horizontal and vertical multi-layer stratification of the
concentration field at the end of a flow-through channel are presented. In the
second example, we demonstrate acoustic tweezing and spatio-temporal
manipulation of a local high-concentration region in a lower-concentration
medium, thereby extending the realm of acoustic tweezing to include
concentration fields.
