Size-Selective Diffusion in Nanoporous but Flexible Membranes for Glucose Sensors

Abstract

A series of nanoporous membranes prepared from polyethylene-block-polystyrene were applied for size-selective diffusion of glucose and albumin molecules. Millimeter-sized test cells for characterization of such molecular diffusions were designed assuming an implantable glucose sensor. The prepared nanoporous membrane exhibits excellent flexibility and toughness compared to conventional nanoporous membranes of brittle alumina. Pore size of the membranes could be controlled from 5 to 30 nm by varying preparation conditions. All of these nanoporous membranes prepared in this study let glucose pass through, indicating a continuous pore connection through the entire thickness of the membrane in a few tens of micrometers. In contrast, membranes prepared under optimum conditions could perfectly block albumin permeation. This means that these vital molecules having different sizes can be selectively diffused through the nanoporous membranes. Such a successful combination of size selectivity of molecular diffusion in nanoscale and superior mechanical properties in macroscale is also beneficial for other devices requesting down-sized manufacture.

Nanoporous polymeric materials: A new class of materials with enhanced properties

“…Other nanoporous polymeric systems such as polyimide [193], polyethylene [194], or polycarbonate (PC) [195] have also been investigated. Smuleac and coworkers [195] demonstrated that the MWCO of Na 2 SO 4 salt was higher in the membranes with lower pore sizes (a difference up to 800% for a feed concentration of 2 mM).…”

Versatile ultrathin nanoporous silicon nitride membranes

“…There have also been studies on thin membrane platforms containing free standing polymer membranes (17)(18)(19), inverse opals (20) as well as protein (21), and block copolymer membranes (22)(23)(24). To provide improved membrane robustness, allow miniaturization, as well as the possibility to integrate with other ionic and electronic devices, silicon-based platforms are the perfect choice.…”

Size-selective diffusion in nanoporous alumina membranes for a glucose affinity sensor

“…From these results, it comes out that the glucose diffusion coefficient in these membranes is only ∼5 times smaller than in water (D = 6.73 × 10 −4 mm 2 /s [16]). Considering the relative standard deviation of 23%, this value is of the same order of magnitude that the diffusion coefficient in a 20 nm asymmetric alumina membrane from Whatman (1.39 × 10 −4 mm 2 /s) and much higher than its value in nanoporous polyethylene membrane (0.18 × 10 −4 mm 2 /s) [2]. This quite high diffusivity is remarkable when considering all possible effects impeding diffusion in nanoporous membranes.…”

“…On the other hand, nanoporous membranes can also be used to confine large sensing molecules provided they exhibit a well defined pore size distribution. Various types of nanoporous membranes have been investigated for biosensors applications, including polymeric membranes [2], micromachined silicon membranes [3] and anodic alumina membranes [4]. With their good structural stability and intrinsic biocompatibility, nanoporous alumina membranes are typically well suited for biosensor size-selective interface.…”