FPGA devices offer interesting solutions for boosting the real-time processing capability of HEP experiments but efficiently dissipating heat is a challenge particularly for the coming dense and high-performance computing systems. Liquid-based cooling is a promising technology for offering a compact and energy-efficient cooling system. We designed, constructed and tested prototypes for liquid-based cooling based on micro-channels etched on silicon wafers. The first batch of prototypes was recently completed at FBK in Trento and tested at INFN laboratories. Preliminary results, confirmed by simulation based on computational fluid dynamics, obtained a heat dissipation capacity of $\sim$6~W/cm$^2$, competitive with traditional heat dissipation methods.