Flexible conductivity-temperature-depth-strain (CTDS) sensor based on a CNT/PDMS bottom electrode for underwater sensing

Abstract

Marine hydrological information has a significant impact on human development and the utilization of the oceans, which can be monitored with underwater sensors. In the past, ocean research has relied on the use of bulky underwater recorders and sensory telemetry networks. In this study, an integrated flexible sensor is developed for underwater conductivity, temperature, depth, and strain (CTDS) detection. Platinum resistance sensors were used for temperature and strain measurements, conductivity sensors with interdigitated electrodes were used for salinity measurements, and capacitive pressure sensors for depth measurements. Two kinds of flexible capacitive pressure sensors were fabricated with a carbon nanotube/polydimethylsiloxane (CNT/PDMS) bottom electrode and copper/polyimide (Cu/PI) bottom electrode. The sensor with the CNT/PDMS bottom electrode outperformed the sensor with the Cu/PI bottom electrode over a wide pressure range (< 5 MPa) and showed stable capacitance up to 1000 cycles. COMSOL simulations also support our experimental results with high sensitivity of the sensor with a CNT/PDMS bottom electrode. The integrated flexible sensor is durable and lightweight, making it ideal for use as a stationary monitoring sensor or for attachment to a variety of marine animals.

Flexible Bioelectronic Tag with a Kirigami‐Based Design for Crosstalk Suppression in Multimodal Sensing

“…[17][18][19] Therefore, flexible and cost-effective wearable sensors are of interest for marine monitoring using aquatic animals. [20][21][22][23] Wang et al developed a flexible triboelectric nanogenerator capable of collecting energy while the host fish swim, thus enabling the monitoring of their swimming behavior. [24] Elsewhere, Pan et al utilized the principles of ion-electron sensing to develop an underwater flexible skin, which was employed for monitoring the velocity and posture of carp fish.…”

“…[ 17–19 ] Therefore, flexible and cost‐effective wearable sensors are of interest for marine monitoring using aquatic animals. [ 20–23 ]…”

Soft, flexible pressure sensors for pressure monitoring under large hydrostatic pressure and harsh ocean environments

“…In the past decade, many flexible pressure sensors have been developed based on soft materials including conductive polydimethylsiloxane (PDMS) composites, 21,22 hydrogels, 23–25 liquid crystal polymers (LCPs), 26,27 and dielectric elastomers. 28,29 The flexible pressure sensors based on soft materials are promising for deep ocean sensing because of their incompressibility under large hydrostatic pressures and, therefore, the potential for eliminating pressure chambers.…”

“…Traditional ocean pressure sensors such as those in cable-controlled underwater vehicles 15,16 and rigid underwater robots 6,17,18 are made of rigid materials, which often need the protection from a pressure chamber to survive the large hydrostatic pressure in the ocean, limiting the flexibility of the sensing systems for integration with many platforms and increasing the size and energy consumption of the sensor system. 19,20 In the past decade, many flexible pressure sensors have been developed based on soft materials including conductive polydimethylsiloxane (PDMS) composites, 21,22 hydrogels, [23][24][25] liquid crystal polymers (LCPs), 26,27 and dielectric elastomers. 28,29 The flexible pressure sensors based on soft materials are promising for deep ocean sensing because of their incompressibility under large hydrostatic pressures and, therefore, the potential for eliminating pressure chambers.…”

Piezo-Resistive Flexible Pressure Sensor by Blade-Coating Graphene–Silver Nanosheet–Polymer Nanocomposite

“…Numerous nanomaterials have been widely used in flexible pressure sensors because of their excellent electrical properties, such as graphene [ 16 ], carbon nanotubes [ 17 , 18 ], and other carbon-based nanomaterials, metal-based nanowires, nano-sheets, and two-dimensional carbides and nitrides (MXenes) [ 19 ]. Researchers have tried many different materials as flexible substrate materials, including paper, silk [ 20 ], poly(ethylene terephthalate) (PET), polyimide (PI), polydimethylsiloxane (PDMS), and so on [ 21 ]. The detection of pressure can be achieved based on the response of resistance [ 22 ], capacitance, piezoelectricity, and triboelectric effect to the pressure [ 23 ].…”