A new approach for an ultra-thin piezoresistive sensor based on solidified carbon ink film
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A new approach for an ultra-thin piezoresistive sensor based on solidified carbon ink film Ying Yi1
, Ayman Samara2, and Bo Wang1,*
1
Division of Information and Computing Technology, College of Science and Engineering, Hamad Bin Khalifa University, Doha 34110, Qatar 2 Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Doha 34110, Qatar
Received: 13 July 2020
ABSTRACT
Accepted: 5 September 2020
Conventional flexible piezoresistive strain sensors that use conductive particles polymer composites exhibit thick structures with a low sensitivity to external tension. This paper presents a cost-effective method to fabricate ultra-thin and highly sensitive piezoresistive strain sensors. In our fabrication steps, carbon ink that is mainly composed of carbon black particles is solidified with a drying process to form a ‘‘paperlike,’’ flexible conductive film. Without any surface modification techniques, the carbon ink film is directly placed onto liquid-state PDMS and then bonded after the drying process. Following the rapid prototyping, different performance metrics of the fabricated sensors, including piezoresistivity, gauge factor, temperature dependency, elastic modulus, and repeatability are measured. Specifically, sensors fabricated with this method show a significantly improved gauge factor (*26) compared to similar flexible sensors fabricated by more complicated micro-fabrication methods. The proposed method of fabrication and the corresponding ultra-thin (*45 lm) sensor prototype may benefit the design and mass production of future wearable biomedical and healthcare sensors.
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The Author(s) 2020
Introduction Flexible and lightweight strain sensors are critical components for applications such as human motion detection [1, 2], touch panels [3, 4], soft robotics [5], electronic skin [6, 7], wearable electronics [8], health monitoring [9, 10]. Typically, a strain sensor exhibits Handling Editor: Maude Jimenez.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05309-8
piezoelectric [11, 12], capacitive [13, 14], or piezoresistive [15–17] transduction to external forces. While piezoelectric materials, such as P(VDF-TrFE), produce electrical charges when mechanical stress is applied [11], the materials are usually stiff [18] and only able to function in conditions of dynamic tension [11], which greatly limits their applications. Capacitive strain sensors are made of 2 parallel
J Mater Sci
conductive electrodes with a dielectric layer between the electrodes. When an external force is applied, the property of the dielectric layer changes, which in turn, leads to a change in capacitance. The sensitivity of the capacitive strain sensor, however, is low when the effective compression applied to the dielectric layer is weak (e.g., a capacitance change ratio of 0.9% at a pulse pressure of 90 kPa [19]). Therefore, piezoelectric and capacitive strain sensors face a challenge to achieve reliable measurements in conditions of static tension and/or weak
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