Garage-Fabricated, Ultrasensitive Capacitive Humidity Sensor Based on Tissue Paper

Abstract

The role of humidity sensors in different industries and field applications, such as agriculture, food monitoring, biomedical equipment, heating, and ventilation, is well known. However, most commercially available humidity sensors are based on polymers or electronic materials that are not degradable and thus contribute to electronic waste. Here, we report a low-cost, flexible, easy-to-fabricate, and eco-friendly parallel-plate capacitive humidity sensor for field applications. The sensor is fabricated from copper tape and tissue paper, where copper tape is used to create the plates of the capacitor, and tissue paper is used as a dielectric sensing layer. Along with the low cost, the high sensitivity, better response and recovery times, stability, and repeatability make this sensor unique. The sensor was tested for relative humidity (RH), ranging from 40% to 99%, and the capacitance varied linearly with RH from 240 pF to 720 pF, as measured by an Arduino. The response time of the sensor is ~1.5 s, and the recovery time is ~2.2 s. The experiment was performed 4–5 times on the same sensor, and repeatable results were achieved with an accuracy of ±0.1%. Furthermore, the sensor exhibits a stable response when tested at different temperatures. Due to the above advantages, the presented sensor can find ready applications in different areas.

Fast Response Facile Fabricated IDE-Based Ultra-sensitive Humidity Sensor for Medical Applications

“…It is then fabricated using PET with small pores as a substrate, non-woven paper as a sensing layer for both the top and bottom sides, and copper tape as a sensing layer for both the top and an electrode because of its high electrical conductivity toward humidity. The sensor is garage-fabricated, as simple hands-on fabrication is done without the need for any such complex tools or devices, such as an inkjet printer, gravure printer, screen printing, or spin coating, which makes our sensor cost efficient in terms of electricity savings which are utilized by a fabrication process through these printers. , The comparison of normal PET and PET with small pores as a substrate is done, and it is experimentally verified that the sensor with the substrate having small pores is highly sensitive compared to the normal PET substrate. Figure shows the fabrication steps of the sensor, with PET having small pores as a substrate.…”

“…Humidity sensors are enormously used to monitor the moisture content or water vapor concentration in the surrounding environment; nowadays, these sensors are used in different fields and commercial applications, including agricultural, food, medical, non-contact sensing, and space applications. , Different types of humidity sensors have been reported previously depending on their working principles, like resistive, impedance, capacitive, heater, or thermal techniques, and the change observed in their physical parameters after exposure to humidity. − The most commonly used humidity sensors are resistive or capacitive. Resistance-based sensors have low cost, but the response is non-linear, has low performance, and cannot be used for sensitive applications.…”

Chitosan-Based Highly Sensitive Viable Humidity Sensor for Human Health Monitoring

“…60 Ullah et al reported a highly sensitive, flexible, and eco-friendly biodegradable nonwoven paper-based humidity sensor on polyethylene terephthalate (PET) substrate with copper tape as electrodes and demonstrated its applications in health and medicine. 61 In recent work, Li et al proposed a flexible humidity sensor based on alkalized MXenes and polydopamine for human−machine interaction in a noncontact manner. 62 Such studies suggest the emerging application of humidity sensors in determining human health severities related to respiration and skin moisture.…”

Highly Sensitive and Flexible Capacitive Pressure Sensors Based on Vertical Graphene and Micro-Pyramidal Dielectric Layer

“…Among these sensors, capacitive sensors with a dielectric layer sandwiched between two electrodes exhibit the advantages of a simple structure, facile manufacturing, low energy consumption, and static/dynamic detection. Therefore, flexible capacitive pressure sensors have attracted extensive attention in tactile sensing [ 16 , 17 ], environmental detection [ 18 , 19 ], and human motion monitoring [ 20 , 21 , 22 ]. High sensitivity is key to achieving high-pressure resolution, which is essential for simplifying signal processing [ 23 ].…”