  Flexible sensors made from organic bilayer films of molecular conductor on
polymeric matrix have attracted many interest due to their simple fabrication
with high potential for being scaled up, and for their high-performing
multi-functionality at room temperatures. In particular, the piezoresistive
property of the organic bilayer film is among one of the highest ever reported,
allowing its utilization in various sensing applications. In this work, we
present the study of the flexural piezoresistivity of an organic bilayer film
based on $\beta-\rm (BEDT-TTF)_2I_3$ on polycarbonate matrix from room
temperatures down to cryogenics temperatures. Non-trivial temperature dependent
profile of the gauge factor is revealed, including enhancement of the gauge
factor from $\sim 18$ at room temperatures to $\sim 48$ at 4.3 K. An organic
bilayer cantilever magnetometer is developed and demonstrated to measure
magnetic properties of a single crystalline organic superconductor $\kappa-\rm
(BEDT-TTF)_2Cu(N(CN)_2)Br$ at temperatures down to $\sim 2.75$ K and magnetic
fields up to 5 T. The high-performing bilayer devices can be fabricated in a
very simple manner, and they are robust and recyclable.
