A Universal Two-Input MEMS Logic Gate

N. Jones, J. Clark
Auburn University,
United States

Keywords: logic, gate

Summary:

We present a MEMS relay structure that can function as any one of the fundamental two-input logic gates: AND, NAND, OR, NOR, XOR, XNOR, IMPLY, NIMPLY, NOT, or BUF. Based on a single MEMS structure, we show how the type of gate logic can be determined by how the electrodes of the MEMS are connected to the two inputs and the power source. This flexibility allows for compact realization of logic but also could prove highly effective as an element in reconfigurable logic. Although all of the logic gate operations listed above can be created by connecting several normal MEMS relays together, by minimizing the number of relays the amount of time required to complete a logical operation can be significantly reduced. Previously, T-K Liu et al. used a planar MEMS device that operated as a NOT, AND, OR, or BUF [1]. They showed that other types of logic gates are possible by combining two or more of their gates, and they also described how their structure is able to eliminate the problem of shoot through current. Similarly, our MEMS gate is able to eliminate crowbar current by using a single moveable cantilever that completely switches between two separate states. However, the reason that we are able to achieve a greater variety of gate types is due to our novel dual electrodes on each cantilever that enable additional logic operations. A universal gate structure facilitates optimization, modularity, and efficiency in spatial chip design. We show that only two materials (insulator + conductor) are required to fabricate the structure. The use of insulating and conductive polymers can be used to form MEMS gates that have a greatly expanded temperature operating range (cryogenic to 340F), far outclassing typical semiconductors which are confined to (about 0F to 120F). As polymers avoid the brittle nature of silicon, this could also prove useful for flexible chips. Using the pull-in phenomenon, current flow is kept to a minimum, which reduces Joule heating in the device. Although there are many ways to fabricate our dual electrode MEMS gates, a 3D printable version[2,3,4,5,6,7], in multiple states of actuation is shown in Figure 1. The connectivity required to achieve the various fundamental logical operations are shown in Figure 2. In the paper we will describe our mathematical model governing the behavior of this new gate and verify the model with finite element analysis.