NSF Convergence Accelerator Track M: Water-responsive Materials for Evaporation Energy Harvesting

Many important physiological functions of plants (e.g., seed dispersal and burial) rely on water-responsive (WR) materials that mechanically deform in response to changes in relative humidity (RH). Recently, biological WR materials have demonstrated the capability to generate significantly higher energy actuation compared to all known muscles and actuators. They have enabled the development of evaporation energy harvesting engines and generators that operate autonomously when placed at a suitable air-water vapor interface. Theoretical and physical studies suggest that these devices are highly scalable and could produce power comparable to current solar and wind farms, while mitigating the intermittency issue that is often experienced by these renewable energy sources. Despite their promise, the development of WR materials and their use in evaporation energy harvesting is still in its infancy and faces a broad array of challenges. The overarching goal of this research is to make transformative progress on a new evaporation energy harvesting technique based on WR materials and move the technique from lab-scale to the real world. The research proposes an innovative and transdisciplinary solution to the global energy transition, forwarding an approach that is cost-effective, non-polluting, and fully sustainable, using bio-inspired analogs of the evaporation phase in the hydrologic cycle to power the next generation of energy harvesting devices. The researchers envision that the proposed convergence research will significantly accelerate the growth of the emerging fields of WR materials and evaporation energy harvesting. Ultimately, this research will establish groundbreaking approaches for society to use the ubiquitous and untapped energy source of natural evaporation for actuation, energy conversion, and environmental protection. The proposed activities will provide resources, research, and training opportunities, greatly benefiting STEM education and contributing to education and workforce development in sustainable design. Through convergent and interdisciplinary approaches that merge biomaterials, chemistry, simulation/artificial intelligence (AI), engineering, product design, techno-economic energy analysis, environmental impact and life-cycle analysis, hydrologic analysis, manufacturing/production, and public policy, we aim to: (i) explore and develop new WR materials; (ii) scale-up the WR material manufacturing using sustainable design principles; (iii) execute system-level prototypes of evaporation energy harvesting devices; and (iv) assess techno-economic feasibility and develop marketing strategies. The proposed work will enhance our understanding of the fundamental WR principles of natural materials, as well as provide general guidelines to engineer nanoscale WR materials into macroscale structures. These insights will guide the design of biologically based WR materials with superior energy/power densities compared to existing actuators, opening up novel opportunities for using sustainable, muscle-like actuators in a wide array of engineering applications. Moreover, the proposed lab-scale prototyping and modeling of the evaporation energy harvesting systems will provide new strategies for utilizing WR materials to drive the rotary motion of mechanical devices sourced through evaporation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.