Performance Enhancement of a Microfabricated Resonator Using Electrospun Nanoporous Polymer Wire

Abstract

A nanoporous poly(methyl methacrylate) (PMMA) wire was prepared by electrospinning under high humidity and attached between two prongs of a microfabricated quartz tuning fork (QTF). Exposure of the QTF to ethanol vapor caused a frequency shift due to a decrease in the modulus of the PMMA wire, and the frequency change increased as the concentration of ethanol vapor increased. The nanoporous wire-coated QTF exhibited higher sensitivity and faster response time than a plain wire-coated QTF, which was attributed to the high surface area and pore networks facilitating the transport of ethanol molecules inside the PMMA wire.

A Review on the Impact of Humidity during Electrospinning: From the Nanofiber Structure Engineering to the Applications

“…Electrospun membranes have been identified as adequate candidates for the elaboration of the active layer of sensors thanks to their high surface area. In order to further increase the surface exposed to the medium to be analyzed, Hwang et al [166] elaborated PMMA ultraporous fibers by electrospinning under high humidity RH = 60%. A single fiber was then transferred between two prongs of a quartz tuning fork (QTF) in order to measure the resonance frequency shift as a function of the amount of ethanol vapor in air.…”

Performance Enhancement of a Quartz Tuning Fork Sensor Using a Cellulose Nanocrystal-Reinforced Nanoporous Polymer Fiber

“…When a polymer fiber was cut by a razor blade, the resonance frequency of the QTF with the polymer fiber residue was almost identical to that of the bare QTF, indicating that the mass effect was not significant. However, the attachment of the P30 fiber to the QTF induced an increase in the frequency [16]. Figure 3b shows that the resonance frequencies of the bare QTF (32.76 kHz) increased by 47, 90, 177, and 420 Hz, respectively, upon the coating of P60, P30, CP60, and CP30 fibers, indicating that the mass loading effect is negligible when compared with the stiffness effect.…”

“…The electrospun fibers were collected on two aluminum foils, which were separated by 2 cm so as to obtain freestanding fibers. The distance between the nozzle and aluminum collector was kept at 15 cm, and the relative humidity (RH) was controlled using a humidifier to maintain a 30% or 60% atmosphere [16]. The following four types of polymer fibers were produced: PMMA fibers obtained at 30% RH (P30) and 60% RH (P60), and CNC-reinforced PMMA fibers obtained at 30% RH (CP30) and 60% RH (CP60).…”

“…The sensitivity of a polymer fiber-coated QTF can be improved by increasing the surface area or modulus of the polymer fiber [15][16][17][18]. The surface area is generally increased by creating porous structures or uneven surfaces on the fiber.…”

Sensory Polymeric Foams as a Tool for Improving Sensing Performance of Sensory Polymers

“…In the last years, the sensory properties of cellular materials have gained a lot of attention, and different research works have been published employing porous materials in sensing applications. For example, Hwang et al developed micro-resonators based on porous nanowires [8], Kumeria et al presented colorimetric sensors using mesoporous silicon crystals [9], Jiang et al prepared humidity sensors employing porous polymeric microspheres [10], and Lee et al prepared fluorescent molecular-scale porous polymeric sensory films for the detection of volatile organic compounds [11]. It is also important to remark that the enhanced sensitivity of foams for analyte detection has also been reported by Wang et al [12], employing the sensing characteristics of polyurethane foams in amine detection, or the classical work of Park et al, in which porous polymeric films are tested in humidity-sensing applications [13].…”