Synthesis and Characterization of Polymer Brushes on Micromechanical Cantilevers

Abstract

Summary: A technique to cover microelectromechanical systems (MEMS), such as micromechanical cantilever (MC) sensors, with a covalently bound brush layer has been developed. The polymer layer was grown using a “grafting‐from” synthesis of polymer brushes under mild conditions, by surface‐initiated atom transfer radical polymerization. Atomic force microscopy (AFM) and ellipsometry have revealed a uniform thickness of about 12 nm from which a grafting density of polymer brushes of 0.19 chains · nm−2 was estimated. The coating with polymer brushes can be realized on a selected surface. It was shown that a single‐sided brush layer swells reversibly in toluene, resulting in a bending of the micromechanical cantilever.Schematic representation of the PMMA brush synthesis on the MC surface, by surface‐initiated ATRP.magnified imageSchematic representation of the PMMA brush synthesis on the MC surface, by surface‐initiated ATRP.

Bimaterial Microcantilevers as a Hybrid Sensing Platform

“…Various methods such as drop casting, [135][136][137][138] spin coating, [139,140] inkjet printing, [133] spray coating, [141,142] capillary painting, [143] plasma polymerization, [144] in situ polymerization, [145][146][147][148] grafting to via SAM functionalization, [149] and matrix assisted pulsed laser evaporation (MAPLE) [150] have been adapted for modifying MCs.…”

“…Indeed, the MC bending specific to the interaction between solvent vapor and polymer with respect to time-and magnitude evolution was exploited for vapor monitoring. [137,141,146,[221][222][223][224][225][226][227][228][229][230][231][232][233][234][235][236] In a typical laboratory test, 0.1 ml of various solvents was placed in vials, and the vapor from the headspace above the liquid was sampled using microcantilever sensor arrays, operated in static deflection mode as a kind of artificial nose (Fig. 20a).…”

Water Soluble Responsive Polymer Brushes

“…This bending is typically monitored using laser and photodiode in an AFM or similar apparatus. Again, the development of versatile surface-initiated radical polymerisation techniques made it possible to covalently graft polymer brush layers to microcantilevers [53], offering a new range of robust responsive coatings. These systems have been used to good effect as chemical sensors [54], and conversely as actuators [55].…”

Quartz crystal microbalance study of the kinetics of surface initiated polymerization

“…Baker et al determined the rate of polymerization (R p ) to be 1-10 nm·h −1 from ellipsometry data [50] . Several groups applied QCM [41,[52][53][54] and cantilever [55] to online monitor SIP. We proposed in a previous report [54] that the linear frequency-thickness (f-T) relation could be applied to convert frequency decrease to thickness increase.…”