Figures (4)  Tables (1)

    • Figure 1. 

      Mechanical energy promotes the evolution of the conceptual paradigm for understanding biogeochemical cycles.

    • Figure 2. 

      Experimental evidence across systems.

    • Figure 3. 

      Mechanism of the biohybrid piezoelectric system. (a) Construction and proposed principle of bio-piezoelectrical hybrid system. (b) Pathway diagram for proposed electron transfer in the biohybrid system.

    • Figure 4. 

      Applications and future perspectives.

    • System function System composition
      		Performance metrics Main limitations Ref.
      Piezoelectric material Microorganism
      Denitrification system Struvite Thiobacillus denitrificans 1. Achieved near 100% NO2− reduction in synthetic wastewater.
      2. Enhanced nitrate removal rate by up to 117% in real wastewater treatment.
      3. Mechanical to electrical energy conversion efficiency of 0.4%.      		 1. The main product is N2O (~64.5%), a potent greenhouse gas, due to ROS inhibition of N2O reductase.
      2. Relatively long reaction time (hours to days).      		 [16]
      Multi-functional metabolic system Barium titanate (BaTiO3) Rhodopseudomonas palustris and other electroactive microorganisms 1. Drove carbon fixation, increasing biomass ~10 fold.
      2. Achieved highly efficient NO3− reduction (near complete).
      3. Successfully applied to various metabolic processes including CH4 production, SO42− reduction, and pollutant degradation.      		 1. Broad but limited applicability: The process relies on the microorganism's ability for extracellular electron uptake and is ineffective for non-electroactive microbes (e.g., E. coli).
      2. Alkaline conditions generated during piezoelectric transduction may create potential oxidative stress for cells.      		 [18]
      Nitrate reduction to ammonia system ZnO Nanorods Shewanella oneidensis MR-1 1. NO3−removal efficiency: 97.97%.
      2. NH4+ production rate: 40.2 μmol·L−1·h−1.
      3. Stability: Maintained 93.4% activity after three cycles.      		 1. Requires optimization of water flow rate (optimal 0.5 m·s−1).
      2. High flow rates may cause separation of materials from cells.
      3. Not yet validated in real wastewater.      		 [19]
      Bioplastic synthesis system ZnO nanosheets Cupriavidus necator 1. Autotrophic culture: PHB production increased over 3-fold (reaching 1,093.5 mg·L−1), efficiency 2.4%.
      2. Heterotrophic culture: PHB production doubled (reaching 8.2 g·L−1), efficiency 6.2%.
      3. Significantly increased intracellular NADPH/NADP+ ratio.      		 1. Ultrasound may cause physical damage to cells at high intensities or prolonged exposure.
      2. H2 produced by piezoelectric materials is insufficient to explain all metabolic enhancement; the process relies on electron shuttles secreted by microorganisms.      		 [51]

      Table 1. 

      Comparison of key bio-piezoelectric systems