Capture and Release of Molecules with Liquid Metals

This paper reports the capture and release of target molecules on gallium-based liquid metal (LM). Functionalizing the native oxide of the LM with (3-aminopropyl)triethoxysilane (APTES) creates an amine-terminated surface capable of binding and thereby capturing a model analyte, fluorescein isothiocyanate. These captured surface molecules can be released by electrochemically reducing the oxide layer. This approach captures ≈81% of the dye from solution and ≈92% of the captured molecules can be released back into solution. Since the oxide reforms spontaneously, the surface can be reused for multiple cycles of capture and release. The liquid nature of the LM allows the surface area of the LM to be varied to control the amount of binding area. It also enables facile integration into microfluidic channels, permitting real-time capture and release in a dynamic fluidic environment. Compared to an electrostatic-based capture and release approach─which uses an applied voltage to trap negatively charged species─the oxide-mediated strategy shows superior stability against the shear forces experienced in a microfluidic environment. Notably, the multilayer APTES coatings and possible dye clustering help to capture more than a monolayer of dye molecules for a given surface area of LM. This methodology demonstrates a versatile proof-of-concept that could be further adapted for integration into lab-on-a-chip devices and for future drug delivery, bioseparation, and sensing applications requiring molecular capture and release.