Photo-modulated fluidic channels for precise delivery of ions and molecules.

Abstract

Fabrication of remote-controlled ion and molecule delivery devices with sub-nanomolar accuracy possesses enormous potential for application in futuristic areas like bio-sensing, molecular machines, energy storage/harvesting, separation, and purification. Here, we combined the excellent photothermal characteristics of oxidised multiwalled carbon nanotubes (o-CNT) with atomically thin 2D sheets of V₂O₅ (VO) to fabricate fluidic devices capable of discharging ions and molecules with sub-nanomolar accuracy. Remarkably, the delivery of ionic/molecular pulses can be remotely modulated through irradiation with IR light. The heterostructured fluidic membrane (HFM), fabricated as a bilayer membrane with distinctive regions of o-CNT and VO, can continuously deliver K⁺ ions at the rate of ∼0.58 nmol min^-1. The ionic flow rate can be further tuned by modulating the thickness and composition of the HFM. Moreover, triangular HFM can discharge ions in nanomolar pluses (∼1.85 to 6.92 nmol per pulse) when remotely triggered through light of different intensities. Likewise, the intermixed fluidic membrane (IFM), fabricated through vacuum filtration of the homogeneous mixtures of the VO and o-CNT, can discharge biologically relevant molecules like tryptophan (Trp) and aspirin at a rate as low as 0.1 nmol min^-1, which can be further modulated with light and heat.