The paper presents a cost-effective 3D-printed bionic hydrogel evaporator (3DP-BHE) designed for stable solar desalination. Inspired by tree transpiration and hierarchical porous structures, the 3DP-BHE is fabricated using a combination of starch and activated carbon (AC) as a solar light absorber. The evaporator features a bionic tree leaf layer for light absorption and vapor diffusion, and a bionic tree trunk layer with a bimodal porous structure for water transfer, thermal isolation, and salt ion convection. This unique structure achieves a stable evaporation rate of 2.13 kg m⁻² h⁻¹ with a 90.5% energy efficiency under one sun. During a 7-day desalination of 10 wt.% brine, the 3DP-BHE maintained a steady evaporation rate of 1.98 kg m⁻² h⁻¹ with a cost-effectiveness of 195.3 g h⁻¹ S⁻¹. The 3DP-BHE's performance is superior to other hydrogel evaporators in terms of salt resistance and cost, making it a promising solution for affordable solar desalination systems on multiple scales.The paper presents a cost-effective 3D-printed bionic hydrogel evaporator (3DP-BHE) designed for stable solar desalination. Inspired by tree transpiration and hierarchical porous structures, the 3DP-BHE is fabricated using a combination of starch and activated carbon (AC) as a solar light absorber. The evaporator features a bionic tree leaf layer for light absorption and vapor diffusion, and a bionic tree trunk layer with a bimodal porous structure for water transfer, thermal isolation, and salt ion convection. This unique structure achieves a stable evaporation rate of 2.13 kg m⁻² h⁻¹ with a 90.5% energy efficiency under one sun. During a 7-day desalination of 10 wt.% brine, the 3DP-BHE maintained a steady evaporation rate of 1.98 kg m⁻² h⁻¹ with a cost-effectiveness of 195.3 g h⁻¹ S⁻¹. The 3DP-BHE's performance is superior to other hydrogel evaporators in terms of salt resistance and cost, making it a promising solution for affordable solar desalination systems on multiple scales.