Session: 06-08: Bioinspired Networks and Neurons

Paper Number: 111131

111131 - Memory in Droplets: Retaining Voltage Signals in Biologically-Inspired Droplet Networks 

Memory in a material is exhibited through the dependence of the material properties on its past history.  This definition is taken in part from the synaptic plasticity observed in connections between neurons, where the connections are strengthened according to their activity and usage. This synaptic plasticity is a necessary step for encoding memories, and these dynamic communicative properties have been proposed as a foundation for building neuromorphic or brain-inspired materials. One proposed approach to the development of neuromorphic materials involves the creation of webs of lipid membranes at droplet-droplet interfaces.  These membranes are constructed using the droplet interface bilayer (DIB) technique, and the application of a voltage signal across DIBs has been linked to transient shifts in the membrane properties, exhibiting memcapacitance and memristance.  Both of these phenomena involve changes in the properties of the membranes based on the history of the applied electrical signals transmitted, providing neuromorphic capabilities.

Recent discussions on the nature of memory have argued that while the synaptic plasticity of the interfaces is a necessary component of learning, it is not a complete description of recollection and memory. Consequently, some additional form of molecular plasticity must be present within the cells themselves.  With this in mind we seek to augment the neuromorphic droplet-based tissues by expanding them to larger networks containing multiple interfaces between collections of droplets.  This leads to the presence of droplets that possess a drifting voltage or internal state.  This internal state provides a form of memory which may be controlled through asymmetric transport across the membranes, enabling long-term retention of the electrical signals.

In this research we interrogate collections of droplets connected by lipid membranes and attached to electrodes with voltage signals and measure the change in their properties.  Select droplets are imbued with the pore-forming agent alamethicin, capable of asymmetric insertion and rendering the membranes temporarily conductive in response to the polarity of the supplied voltage pulse.  The activation of the alamethicin channels enables the exchange of charge between the droplets, which may then be trapped within the droplets once the voltage signal is released and providing a form of memory by redistributing the charges away from equilibrium.  This is measured through changes in the equilibrium membrane dimensions over periods of time.  The findings demonstrate long-term adaptation of the interfaces through the redistribution of charge in a simple brain-inspired material.

Presenting Author: Braydon Segars University of Georgia

Presenting Author Biography: Braydon Segars is a graduate research assistant working in the Biomembranes Engineering Laboratory at the University of Georgia. His research includes the assembly of complex lipid interfaces and developing brain-inspired materials.