In this contribution, I will present a novel detection technique for low-energy antideuterons in cosmic rays, a promising signature of dark matter annihilation. Sub-GeV antideuterons represent an exceptionally clean channel for dark matter searches: their secondary production through conventional astrophysical processes (inelastic collisions of primary cosmic rays with interstellar medium) is extremely rare at low energies, making the expected background essentially negligible. Consequently, even a few detected events would constitute a significant signal potentially attributable to dark matter annihilation or decay in the Galactic halo. Current dark matter models predict antideuteron fluxes several orders of magnitude above the astrophysical background in the sub-GeV range, motivating the development of novel detection techniques optimized for this energy window.

PLASTICAMI is a segmented plastic tracker designed to identify a distinctive "double pion-star" topology characteristic of antideuteron annihilation: when an antideuteron stops in hydrogen-rich plastic, one antinucleon annihilates promptly, while the second survives with kinetic energy, travels several centimeters, and annihilates after nanoseconds. This spatial separation and timing delay between two annihilation vertices creates a unique double-vertex signature. The detector consists of 30 segmented plastic scintillator layers (3×3 m²) stacked with gaps to resolve these displaced vertices, combined with external Cherenkov veto layers based on the newly characterized FB118 wavelength-shifting plastic for efficient background rejection. Geant4 simulations demonstrate 90% efficiency for identifying antideuterons while rejecting 99% of proton background. Considering atmospheric and geomagnetic effects for Antarctic balloon flights, two missions could achieve sensitivity of ~2×10⁻⁶ (m²sr s GeV/n)⁻¹ in the 100-600 MeV/n range, enabling exploration of theoretically motivated dark matter scenarios. Construction of a prototype detector subsystem is ongoing at INFN-TIFPA, utilizing SiPM photodetectors from FBK and custom front-end electronics.