(268b) An Integrated Ionic Logic Circuit for Addressing/Reading Multiplex Sensor Platform

We present an integrated ionic logic circuit based on a novel fluid-based memristor and crossbar logic. The designed ionic logic circuit is used to address and read individual sensors in a large array with a single input. The circuit stores and retrieves intermediate signals in the circuit that come from an ion-selective membrane sensor array developed by our group (Annual Review of Analytical Chemistry, DOI: 10.1146/annurev-anchem-071213-020155; Biosensors and Bioelectronics, doi.org/10.1016/j.bios.2014.04.008.) These membrane sensors exhibit nonlinear I-V and rectification features, which allow optimum integration with the memristor to produce nonlinear circuit components with binary states, i.e. on-off logic components.  A binary sequence at the input activates the various sensors and the sequence at the output reports the reading. The fluid-based memristor used for constructing circuit is achieved by a memristive phenomenon between silicon microelectrode and aqueous solution, due to a continuous formation of an oxide film on the silicon electrode under anodic polarization. This memristor can be simply fabricated by conventional silicon technology. The confined silicon microelectrode is defined by using thick silicon dioxide spacer, while the metal contact and on-chip counter electrode are made by lift-off technique. An optimal design that allows an on/off ratio larger than 10 and a short switching time less than 100ms of this memristor, accompanied with an operating current in microfluidic range will be presented. Employing crossbar logic, ionic logic circuit units, such as microfluidic latches and NAND/NOR gates, are built by embedding these fluid-based memristors on the microfluidic channel sidewalls. Under this logic configuration, all ionic signals from input and sensor units is delivered through ion migration in the microfluidic channels, while all logic computing operations are completed at the sidewall silicon microelectrodes. This fabrication strategy allows easy integration within our membrane sensor platform, without increasing fabrication complexity and system size. The microfluidic coder and decoder are built subsequently by this logic configuration for addressing and reading each sensor followed a binary sequence signal. The optimization and fabrication details of each logic units will be presented.