| dc.description.abstract | Lower Body Negative Pressure (LBNP) has long been explored as a countermeasure to the physiological deconditioning and orthostatic intolerance associated with prolonged microgravity exposure. Traditional LBNP systems, however, are large, stationary devices that require astronauts to remain immobile during use, limiting their integration into daily spaceflight routines. Although more mobile LBNP solutions have emerged, they remain cumbersome and uncomfortable, ultimately still restricting multitasking and reducing operational feasibility. This study introduces the Soft Kinetics INterface (S.K.I.N.), a flexible, wearable structure designed to support the application of localized LBNP. The goal was to evaluate whether targeted negative pressure applied through the S.K.I.N. could replicate the fluid shift effects of a traditional LBNP chamber while improving comfort, mobility, and time-efficiency. The human thigh was chosen as the focus of this technology demonstration due to its known responsiveness to LBNP and its suitability for small-scale implementation. The development of the S.K.I.N. began with finite element modeling (FEM) to identify optimal material properties and structural geometry. Iterative physical prototyping resulted in a sinusoidal silicone waveform design, selected for its mechanical stability and user comfort. The final prototype was then evaluated in three experimental phases: (1) mechanical testing using pressure-sensitive film to assess structural integrity under vacuum, (2) an ex-vivo pig leg study to validate experimental protocols and assess the S.K.I.N.’s ability to induce fluid shifts, and (3) a human study (n=10) comparing fluid shifts between the S.K.I.N. and a scaled-down version of the traditional LBNP chamber. On average, results from the human study showed that the S.K.I.N. successfully induced localized fluid shifts similar to those of the chamber. However, response magnitude varied considerably across participants. Most of the observed effect was driven by female participants, who exhibited more pronounced fluid shifts, while most male participants showed minimal or no measurable response. FEM simulations supported this finding, suggesting that higher fat-tomuscle ratios — more common in women — may enhance tissue deformability and volume displacement, thereby facilitating greater fluid shifts under negative pressure. Although these differences limit generalizability, they also highlight the potential for the S.K.I.N. to serve as a more targeted countermeasure for specific physiologies or user groups. Although the current S.K.I.N. design’s limited surface area constrains its overall effect, the concept shows promise. The ability to deliver targeted fluid shifts in a more mobile, comfortable format could enable integration into dynamic operational settings. Future work should focus on expanding the system to cover larger areas, such as a whole-pants version, and incorporating a portable vacuum source for mobility in both spaceflight and terrestrial applications. Larger, more diverse participant cohorts will also be necessary to assess long-term usability, efficacy, and individual variability in response. | |
