Mechanotransduction of Multi-Hair Droplet Arrays

Early embodiments of droplet interface bilayer (DIB)-based hair cell sensors demonstrated the capability of sensing discrete and continuous perturbations, including single flicks and constant airflow, respectively, of a hair structure that is held in close proximity to a single lipid membrane. In those studies, the use of a single bilayer formed between a pair of droplets provided the necessary environment for studying the physical mechanism of mechanotransduction of a membrane-based sensor as well as the sensitivity and directionality of the assembly. More recently, we showed that additional lipid-coated droplets could be connected in series to form multi-bilayer arrays. Measurements of bilayer current through each interface demonstrated that perturbation of the hair creates a vibration that propagates across several droplets, allowing for the additional interfaces to also sense the perturbation. Depending on the location of the hair in the droplet array, these sensing currents can occur in-phase with one another, allowing for a total sensing current to be easily summed. Two important remaining questions about multi-bilayer arrays include: 1) How is signal propagation affected by the configuration of droplets in the array? 2) How does perturbation of multiple hair structures affect signal propagation and sensing currents in a droplet-array? To study these questions, we form linear series and L-shaped arrays of DIBs where each droplet is instrumented with a sensing electrode. Our experiments show that the motion of the perturbed hair can be transduced by up to three membranes away from the hair and that a change in the orientation of successive interfaces does not significantly affect the propagation of vibrational energy. Separately, experiments on serial arrays with multiple hairs indicate that a second, unperturbed hair does not affect bilayer currents generated by the perturbed hair and that hairs of varying length can add frequency selectivity and stimulus localization capability to multi-bilayer sensors.