Lithography-Based Fabricated Capacitive Pressure Sensitive Touch Sensors for Multimode Intelligent HMIs

Interdigitated capacitive (IDC) sensors have been extensively researched for human-machine interfaces (HMIs) due to consistent response and easy manufacturing. However, the manual fabrication process and single mode of operation, like buttons, limit their use for future developments of HMIs. We reported a maskless laser lithography-based fabrication process for developing chromium metal electrodes on glass. Chromium metal fabricates sensors on a glass substrate because of its durability. IDC touch sensors are sensitive to the pressure of human finger touch to perform multimode of operation intelligently by distinguishing between no touch, low-pressure touch (LPT) and high-pressure touch (HPT). Sensors exhibit similar to 25 pF/N sensitivity for the force of finger touch, 0.4-sec response, recovery time and durability > 20,000 tests. Touch sensors are arrayed to create pressure-sensitive multimode HMIs for wireless and intelligent mouse cursor movement (MCM) control, numeric keyboard, and smart door locking (SDL) system. Six capacitive pressure sensitive (CPS) sensors-based HMIs utilized to control the low and high speed of the mouse cursor in all four directions and perform the left and right click operations. Numeric keyboard of eight CPS sensors is developed to respond wirelessly to numbers and special characters to a laptop. SDL system demonstrated using the CPS HMI consists of numeric sensors from 0-9, reset and done sensors to utilize it for security applications. HMI sensors responded numerically (0-9) for LPT and special characters for HPT. An algorithm is developed to operate the HMI for the SDL system and use special characters along with numeric, which immensely increases the strength of passwords for security applications. With daily life using substrate material glass, multimode of operation, easily arrayed, and customization, the presented HMIs have the potential to contribute to future developments in intelligent user interfaces, portable computer peripherals, security applications, ATMs, and smart home systems.