Polydimethylsiloxane brushes and the search for extraterrestrial life

Abstract

The low temperature and high pressure tribological properties of polydimethylsiloxane brushes with ice are explored to demonstrate their feasibility as an exterior coating for an off-world cryobot. Successful deposition of the brushes on silicon and glass was confirmed with a contact angle hysteresis < 2° and a surface roughness below 1 nm. The friction factor of the brushes roughly doubled when the temperature was lowered from +20 °C to -20 °C, but it decreased by 55% when the normal force was increased from 0.5 N to 16 N. When sheared, adhered ice slid on the brushes at a shear stress around 21 kPa, and this did not increase with an additional normal pressure of up to 98 kPa. A glass rod coated with the brushes served as a cryobot surrogate and was frozen within cores of -10 °C ice 1 – 3 cm high. Weight attached to the rod enabled it to cleanly slide completely through the ice cores at the ambient -10 °C, i.e. without melting the ice. Together, these results indicate that polydimethylsiloxane brushes may be a feasible exterior coating for an off-world cryobot that would enable it to slide through the frozen surface of potentially life-harboring bodies such as Europa or Enceladus, avoiding the need to melt the entire cryobot’s exterior.

Sustainable design of non-fluorinated yet oleophobic fibrous surfaces

“…Polydimethylsiloxane brushes have been used in recent years as a substitute for uorinated surface chemistries to render surfaces water and oil repellent. [28][29][30][31][32][33] PDMS brushes consist of nanoscale linear siloxane chains that are covalently bonded to a solid surface by one end of the chain. The other end remains free (Fig.…”

Molecularly Capped Omniphobic Polydimethylsiloxane Brushes with Ultra‐Fast Contact Line Dynamics

“…Polydimethylsiloxane (PDMS) brushes are surface-tethered, linear polymer chains that exhibit ultra-low adhesion to liquid droplets, resulting in superomniphobic textiles, [4,5] ice-phobic coatings, [6,7] and lossless liquid transportation. [8,9] However, recent evidence suggests that PDMS brushes have high contact line relaxation time, effectively indicating that they exhibit low static friction but high kinetic friction.…”