EAGER: Safe Direct Sound Printing: De-risking Thermo-acoustic Phenomena in Non-invasive Deep Tissue Bioprinting

The ability to build or repair biological structures inside the human body without open surgery has long been a goal of medicine and manufacturing, with the potential to reduce infection risk, recovery time, pain, and healthcare costs. Existing bioprinting approaches rely on light or heat to solidify materials, which limits their use to shallow or externally accessible regions because these energy sources cannot penetrate deeply into biological tissues. Ultrasound, by contrast, can travel through the body safely and precisely, offering a fundamentally new pathway for non-invasive bioprinting. Recent advances have shown that ultrasound can trigger material solidification at depth, but a critical barrier remains: the lack of scientific understanding needed to ensure that this process can be performed safely in the presence of living cells. This EArly-concept Grant for Exploratory Research (EAGER) project addresses that barrier by focusing on the cell-level safety of ultrasound-driven bioprinting. By identifying how ultrasound exposure, material chemistry, and protective strategies interact to affect cell survival, the research advances fundamental knowledge at the intersection of physics, chemistry, and biology. The outcomes will inform the responsible development of non-invasive manufacturing technologies with broad implications for regenerative medicine, minimally invasive therapies, and advanced manufacturing. The project also contributes to workforce development by training students in interdisciplinary research spanning biomaterials, ultrasound physics, and cell biology, supporting the national interest in scientific leadership and innovation. The goal of this EAGER project is to establish a predictive, cell-level safety framework for ultrasound-induced bioprinting by systematically de-risking the mechanical, thermal, and chemical effects experienced by living cells during material solidification. The research focuses on in vitro and ex vivo systems and deliberately excludes tissue-scale translation to concentrate on fundamental cellular mechanisms. The approach integrates multiphysics modeling of acoustic pressure, cavitation behavior, and sonothermal heating with experimental studies of bioink formulation, polymerization chemistry, and cell encapsulation strategies. Candidate inks will be engineered to balance polymerization efficiency with reduced radical generation and thermal exposure, while encapsulation architectures will be evaluated for their ability to shield cells from mechanical stress and transient heating. Cell viability, membrane integrity, and stress responses will be quantitatively assessed to define safe operating windows for ultrasound exposure. The expected outcomes include validated design rules for cell-compatible inks, quantitative exposure limits, and mechanistic insights into how ultrasound-driven polymerization can transition from damaging to constructive at the cellular level. These results will provide the foundational knowledge required for future advances in non-invasive bioprinting and ultrasound-based manufacturing technologies. 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.