Abstract
Flexible pressure sensors have attracted tremendous attention from researchers for their widely applications in tactile artificial intelligence, electric skin, disease diagnosis, and healthcare monitoring. Obtaining flexible pressure sensors with high sensitivity in a low cost and convenient way remains a huge challenge. In this paper, the composite dielectric layer based on the mixture of carbon nanotubes (CNTs) with different aspect ratios and polydimethylsiloxane (PDMS) was employed in flexible capacitive pressure sensor to increase its sensitivity. In addition, the screen printing instead of traditional etching based methods was used to prepare the electrodes array of the sensor. The results showed that the aspect ratio and weight fraction of the CNTs play an important role in improving the sensitivity of the printed capacitive pressure sensor. The prepared capacitive sensor with the CNTs/PDMS composite dielectric layer demonstrated a maximum sensitivity of 2.9 kPa−1 in the pressure range of 0–450 Pa, by using the CNTs with an aspect ratio of 1250–3750 and the weight fraction of 3.75%. The mechanism study revealed that the increase of the sensitivity of the pressure sensor should be attributed to the relative permittivity increase of the composite dielectric layer under pressure. Meanwhile, the printed 3 × 3 and 10 × 10 sensor arrays showed excellent spatial resolution and uniformity when they were applied to measure the pressure distribution. For further applications, the flexible pressure sensor was integrated on an adhesive bandage to detect the finger bending, as well as used to create Morse code by knocking the sensor to change their capacitance curves. The printed and flexible pressure sensor in this study might be a good candidate for the development of tactile artificial intelligence, intelligent medical diagnosis systems and wearable electronics.
Highlights
Flexible pressure sensors have attracted widely attentions in the area of mobile bio-monitoring of disease diagnosis, tactile artificial intelligence, electric skin and healthcare services because of their real-time, convenient, and wearable features [1,2,3,4,5,6,7]
Foosirtealdl itehlecCtrNicTssinficlrlearsewaisththdeifmfearessntfraascptieocnt roaftiCosN, Tthseinreclraetaivseinpge.rmFoitrtiivnistiteasnocef,ththeeCrNelTast/iPvDe MpeSrmcoimttipvoitsyiteofdtiehleecctorimcspionscirteeadseiealsecthtreicmuassisnfgraCcNtioTns ofifllCerNsTwsiitnhctrheeasaisnpge.cFtorraitniostoafn2c0e,0t–h6e00resllaitgihvetlypeinrmcrietatisveistytoof6.t6hewchoemnpthoseitme adsiselfercatcrtiicounsoinf gCCNNTsTrsefailclheress with the aspect ratio of 200–600 slightly increases to 6.6 when the mass fraction of carbon nanotubes (CNTs) reaches at 6 wt.%, which is 2.75 times to that of pure PDMS. While for both the CNTs fillers with the aspect ratios of 500–3000 and 1250–3750, their mass fraction related relative permittivity curves show an obvious increase when the CNTs mass fractions reach a certain values
For the CNTs filler with the aspect ratio of 500–3000, the relative permittivity of the composite sharply increases at the CNTs at 6 wt.%, which is 2.75 times to that of pure PDMS. While for both the CNTs fillers with the aspect ratios of 500–3000 and 1250–3750, their mass fraction related relative permittivity cMuircrvoemsacshhinoews 20a1n9,o1b0,vxioFOuRs iPnEcErReaRsEeVwIEWhen the CNTs mass fractions reach a certain values
Summary
Flexible pressure sensors have attracted widely attentions in the area of mobile bio-monitoring of disease diagnosis, tactile artificial intelligence, electric skin and healthcare services because of their real-time, convenient, and wearable features [1,2,3,4,5,6,7]. Among different types of flexible pressure sensors, the capacitive sensor owning the advantages of low energy consumption, fast response time, low detection limit and good sensing stability is the research hot topic in recent years [8,9]. Remarkable efforts have been made to improve the sensitivity of flexible capacitive sensors. It should be noticed that the electrode area (A/A0) of the sensor is usually unchanged when the vertical pressure is applied Increase the distance change between two electrodes (d0/d) and the relative permittivity change of the dielectric layer (εr/εr0) under pressure.
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