Facile Pressure-Sensitive Capacitive Touch Keypad for a Green Intelligent Human–Machine Interface

Abstract

There is a great demand for human–machine interfaces (HMIs) in emerging electronics applications. However, commercially available plastic-based HMIs are primarily rigid, application-specific, and hard to recycle and dispose of due to their non-biodegradability. This results in electronic and plastic waste, potentially damaging the environment by ending up in landfills and water resources. This work presents a green, capacitive pressure-sensitive (CPS), touch sensor-based keypad as a disposable, wireless, and intelligent HMI to mitigate these problems. The CPS touch keypads were fabricated through a facile green fabrication process by direct writing of graphite-on-paper, using readily available materials such as paper and pencils, etc. The interdigitated capacitive (IDC) touch sensors were optimized by analyzing the number of electrode fingers, dimensions, and spacing between the electrode fingers. The CPS touch keypad was customized to wirelessly control a robotic arm’s movements based on the touch input. A low-pressure touch allows slow-speed robotic arm movement for precision movements, and a high-pressure touch allows high-speed robotic arm movement to cover the large movements quickly. The green CPS touch keypad, as a disposable wireless HMI, has the potential to enforce a circular economy by mitigating electronic and plastic waste, which supports the vision of a sustainable and green world.

Recent Progress of Tactile and Force Sensors for Human–Machine Interaction

“…The distance is reduced with the increase of the applied pressure; thus, the capacitance is continuously increased with the increment of the pressure [ 43 ]. Another type of capacitive pressure sensor is called an interdigital pressure capacitor, which has also been reported for tactile sensing [ 44 ]. Various elastic materials, including Polydimethylsiloxane (PDMS) [ 45 ], Ecoflex [ 46 ], and Polyurethane (PU) [ 47 ], are utilized as the elastic medium of capacitive sensors.…”

Paper-based wearable ultra-sensitive strain sensors for fitness monitoring

“…By prioritizing environmental safety, the paper proves itself a promising substitute for the development of sustainable conformal gadgets. Paper is a promising candidate for making flexible sensors like humidity sensors [17], pressure sensors [18][19][20], gas sensors [21], etc, as it adheres to biodegradability properties and is lightweight, cost-effectiveness is also an unavoidable factor. Several works on paperbased strain sensors have been reported in the past few years.…”

Paper-based facile capacitive touch arrays for wireless mouse cursor control pad

“…This is the biggest factor behind the present spike in users as they move to a world with effective wireless options. These wireless devices, such as wireless mouse [ [29] , [30] , [31] ], headphones, and keyboards [ 32 ], have the major benefit of clearing up the mess of wires surrounding the workspace. The convenience of work and refinement of the finished product may therefore improve.…”