UC Irvine

The use of membranes with a single pore to measure particles as they pass through is a promising method to allow the rapid determination of properties of individual particles in solution. However, this will involve an understanding and control of the forces that these particles undergo while in the pore. In this work we use single cylindrical pores in PET membranes to test and compare the translocations of deformable hydrogel particles and rigid polystyrene spheres. We find that the hydrogel particles cause a characteristic initial increase in current, pass by electroosmosis, and can also undergo dehydration and deformation in pores of smaller diameter. We also show that the force on a particle by an applied hydrostatic pressure gradient can be sufficiently balanced with a transmembrane voltage that is dynamically triggered when the particle enters the pore, and the subsequent fluctuations in the current from the particle diffusing within the pore can be observed for tens of seconds. Finally, we show that repeated translocations of a single particle can be performed using a set rising edge or falling edge triggered voltage wave, or an even greater number of repetitions can be achieved by subtracting in real time the capacitance effects based on a previous test pulse.