Self-Cleaning Seals

This NASA innovation applies the concepts of electrodynamic dust shielding (EDS) to develop seals (e.g., O-rings) with active self-cleaning capabilities. NASA’s self-cleaning seals are manufactured in the following manner: A seal with a conductive surface (or otherwise fabricated to be conductive) is generated and an electrical connection, lead or electrode is attached. Next, a dielectric material is coated or placed over the conductive surface of the seal. (NOTE: Using conductive elastomer materials eliminates the need for a conductive cover layer) A high voltage (nominally >1kV) power supply is connected to the conductive layer on the seal and grounded to the metallic groove or gland that houses the seal. Given the design, dust accumulates on the outer dielectric layer (a high-voltage insulator) of the seal. To clean the seal, a time varying alternating voltage is applied from the power supply, through the high voltage lead and onto the conductive layer of the seal. When this voltage is applied, the resulting electric field produces Coulomb and dielectrophoretic forces that cause the dust to be repelled from the sealing surface. In practice, NASA’s self-cleaning seals could be operated in continuous cleaning mode (actively repelling dust at all times, preventing it from ever contacting the seal surface) or in a periodic cleaning cycle mode (removing dust from the seal surface at regular intervals). NASA’s self-cleaning seals have been prototyped and demonstrated to be highly effective at dust removal. The invention could serve as the basis of an active, self-cleaning seal product line marketed for in-space and/or terrestrial applications. Additionally, companies developing space assets destined for operation on dusty planetary surfaces (e.g., the Moon) may be interested in leveraging the technology to protect seals from dust/regolith accumulation, ensuring continuous low leakage operations. In space applications, seals for hatches, suit ports, airlocks, and docking systems for pressurized volumes such as habitats, rovers, and space suits must be kept clean. This is necessary to achieve the extremely low leak rates required to ensure that crews will have sufficient breathable air for extended missions on planetary surfaces. Dusty environments, such as those of the Moon and Mars, pose challenges because seals (elastomeric and otherwise) – as dust accumulates on them – will no longer perform as designed, substantially increasing leak rates. Similarly, terrestrial applications involving environments with high dust concentration and pressurized systems (e.g., mining, material handling) must maintain clean seals to ensure safety and uptime. Motivated by the hazard lunar regolith poses to seals – and thus to achieving a sustained lunar presence – researchers in the Electrostatics and Surface Physics Laboratory at NASA’s Kennedy Space Center (KSC) have developed seals that actively self-clean in a continuous or periodic manner.