Reversible mechanical actuation of elastomeric nanopores

Abstract

Mechanical resizing of individual nanopores in a thermoplastic polyurethane elastomer has been characterized. Specimen nanopores were conical, with smaller hole dimensions of the order of tens to hundreds of nanometres. Electrophoretic current measurements show that the estimated nanopore radius can be reversibly actuated over an order of magnitude by stretching and relaxing the elastomer. Within a working range of stretching, current is proportional to specimen extension to the power of a constant, n, which ranges from 0.9 to 2.3 for different specimens. The data indicate that scaling of the effective pore radius is super-affine. At strains below the working range, the pore size is relatively unresponsive to stretching. Macroscopic elastomer extension has been related to local radial strain (50-250 µm from the pore) using optical microscopy. Scanning electron microscopy and atomic force microscopy have been used to observe membrane surface features.

Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores

“…Applied pressure was À 372 6 20 Pa, and pore openings can be imaged using scanning electron microscopy (SEM), 30,[32][33][34][35] with specimens similar to the type used (classified NP1000 by Izon Science) having typical opening radii of 2.6 and 19.7 lm when the specimen arm length is extended to 45 mm. 73 A constriction below the pore surface is suggested by the membrane topography imaged by atomic force microscopy, 32 and this is not inconsistent with confocal microscopy 33 and SEM. 35 Closer comparison of fitted and experimental parameters would need to incorporate uncertainty in two further values, the electrolyte resistivity (q ¼ 0.75 X m) which is assumed homogeneous, and the membrane thickness (d ¼ 159 lm), which is obtained using a hyperelastic material model of pore actuation.…”

“…The sophistication of resistive pulse sensing has also increased, making use of channels made from carbon nanotubes, 17,18 glass, [19][20][21][22][23] silicon, 5,8,15,24 polymers, [25][26][27][28] and elastomers. [29][30][31][32][33][34][35][36][37][38] Resistive pulses can now be used for study and measurement of particle size, 2,3,17,18,20,21,34 concentration, 33 and charge. 17,38 There is clear potential to extend applications towards sensing of complicated dynamic interactions 24 and specific particle shapes.…”

“…31 The ionic current passing through a TP can vary by at least an order of magnitude when the pore is stretched. 32 Therefore, any individual pore specimen has considerable versatility relating to the size of particles it can analyze. TPs can be manufactured to target any particular particle type(s) of the order of tens of nanometers or larger, and sensing of individual DNA plasmids has been reported.…”

Tunable Resistive Pulse Sensing: Potential Applications in Nanomedicine

“…TRPS is an adaptation of RPS in which utilises a conical tunable elastomeric pore that can be stretched or relaxed to change the pore size to suit the sample [11,13,[15][16][17][18][19]. Tunable pore membranes are made of thermoplastic polyurethane and the pores are introduced by mechanical puncture.…”

“…The membrane can be stretched in a biaxial direction to alter the pore size. The size of the pore can be altered as much as an order of magnitude [17].…”