  In the standard approach to studying wormhole geometry, the presence of dark
energy is unavoidable to ensure traversability. The dark energy provides the
negative gravity effect to keep the throat open. The question we analyse is
whether the same can be achieved without dark energy. It turns out that if we
couple the trace of energy-momentum with the standard Einstein-Hilbert
Lagrangian and utilise a sppecific equation of state then dark energy may be
obviated. The Casimir stress energy is known to result in the violation of the
null energy condition (NEC) on the energy momentum tensor. This phenomenon
makes such an equation of state (EoS) an ideal candidate to generate
traversable wormhole (WH) geometries. The laboratory proven phenomenon provides
a mechanism to sustain an open WH throat without having to appeal to dark
energy. We generate two classes of WH solutions with this in $f(R,T)$ gravity
theory, where $R$ represents the Ricci scalar and $T$ is the trace of the
stress-energy tensor. For the background geometry we choose a static and
spherically symmetric metric, and derive the field equations for exact WH
solutions. For the specific choice of the Casimir EoS relating the
energy-momentum tensor components [ Kar and Sahdev: Phys. Rev D {\bf 52} 2030
(1995)] and different choices for redshift functions, we determine the WH
geometry completely. The obtained WH solutions violate the NECs and all
qualitative constraints demanded of physically realisable WHs are satisfied.
This is demonstrated via graphical plots for a suitably chosen range of values
of the $f(R,T)$ coupling parameter. Furthermore, our study involved an
investigation into the repulsive effect of gravity, which revealed that its
presence leads to a negative deflection angle for photons traveling along null
geodesics.
