Contactless Pulsed and Continuous Microdroplet Release Using Photothermal Liquid Crystals

• Published in: Advanced functional materials Vol. 32; no. 44
• Main Authors: Beyazkilic, Pinar, Akcimen, Samet, Elbuken, Caglar, Ortaç, Bülend, Cai, Shengqiang, Bukusoglu, Emre
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01-10-2022
• Subjects: Aqueous solutions; Dopamine; droplet release; Droplets; drug delivery; Emulsions; Hydrogen peroxide; Internal flow; Liquid crystals; Luminous intensity; Materials science; NIR light; Oxidation; photothermal heating; Reagents; Stimulation; Water drops
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202205385

Targeted, on‐demand delivery has been of interest using materials responsive to environmental stimuli. A delivery technique based on precise release of aqueous microdroplets from a liquid crystal (LC) medium with contactless stimulation is presented. A nematic LC is doped with a photothermal dye that produces heat under near IR light exposure. The heat is used to overcome the elastic strains in the LC phase, promoting the release of initially entrapped water droplets to the neighboring aqueous solution. Designing the geometry of LC‐based emulsions and tuning the light intensity and position allows for manipulation of the release in two distinct modes defined as pulsated and continuous. In the pulsated mode, water droplets are released transiently from the casted water‐in‐LC emulsion layer based on sweeping by the moving isotropic‐nematic phase boundary controlled by light. In the continuous mode, water droplets are ejected continuously from a droplet‐shaped water‐in‐LC emulsion, due to a heating‐induced internal flow controlled by light. The droplet release by contactless stimulation is used for the on‐demand dosing of dopamine and its oxidizing reagent from isolated reservoirs to obtain an in situ reaction signal for a hydrogen peroxide assay. A new dual‐mode release system developed with photothermal LCs holds potential in drug release, controlled mixing, and photothermal therapy.
A novel remotely controlled droplet release mechanism is presented. Photothermally‐functionalized liquid crystal that generates heat under NIR laser excitation is used for the on‐demand release of water droplets via pulsated mode or continuous mode. The former is based on the transition of the liquid crystal to the isotropic phase while the latter is based on convection‐induced shearing.