Piezoelectric Behaviour in Biodegradable Carrageenan and Iron (III) Oxide Based Sensor.

This paper is dedicated to the research of phenomena noticed during tests of biodegradable carrageenan-based force and pressure sensors. Peculiar voltage characteristics were noticed during the impact tests. Therefore, the sensors' responses to impact were researched more thoroughly, defining time-dependent sensor output signals from calibrated energy impact. The research was performed using experimental methods when a free-falling steel ball impacted the sensor material to create relatively definable impact energy. The sensor's output signal, which is analogue voltage, was registered using an oscilloscope and transmitted to the PC for further analysis. The obtained results showed a very interesting outcome, where the sensor, which was intended to be piezoresistive, demonstrated a combination of behaviour typical for galvanic cells and piezoelectric material. It provides a stable DC output that is sensitive to the applied statical pressure, and in case of a sudden impact, like a hit, it demonstrates piezoelectric behaviour with some particular effects, which are described in the paper as proton transfer in the sensor-sensitive material. Such phenomena and sensor design are a matter of further development and research.

Stretch Sensor: Development of Biodegradable Film.

This article presents research on biodegradable stretch sensors produced using biological material. This sensor uses a piezoresistive effect to indicate stretch, which can be used for force measurement. In this work, an attempt was made to develop the composition of a sensitive material and to design a sensor. The biodegradable base was made from a κ-carrageenan compound mixed with Fe2O3 microparticles and glycerol. The influence of the weight fraction and iron oxide microparticles on the tensile strength and Young's modulus was experimentally investigated. Tensile test specimens consisted of 10-25% iron oxide microparticles of various sizes. The results showed that increasing the mass fraction of the reinforcement improved the Young's modulus compared to the pure sample and decreased the elongation percentage. The GF of the developed films varies from 0.67 to 10.47 depending on composition. In this paper, it was shown that the incorporation of appropriate amounts of Fe2O3 microparticles into κ-carrageenan can achieve dramatic improvements in mechanical properties, resulting in elongation of up to 10%. The developed sensors were experimentally tested, and their sensitivity, stability, and range were determined. Finally, conclusions were drawn on the results obtained.

Biodegradable Carrageenan-Based Force Sensor: An Experimental Approach.

The development of low-cost biodegradable pressure or force sensors based on a carrageenan and iron (III) oxide mix is a promising way to foster the spread of green technologies in sensing applications. The proposed materials are inexpensive and abundant and are available in large quantities in nature. This paper presents the development and experimental study of carrageenan and iron (III)-oxide-based piezoresistive sensor prototypes and provides their main characteristics. The results show that glycerol is required to ensure the elasticity of the material and preserve the material from environmental impact. The composition of the carrageenan-based material containing 1.8% Fe2O3 and 18% glycerol is suitable for measuring the load in the range from 0 N to 500 N with a sensitivity of 0.355 kΩ/N when the active surface area of the sensor is 100 mm2. Developed sensors in the form of flexible film have square resistance dependence to the force/pressure, and due to the soft original material, they face the hysteresis effect and some plastic deformation effect in the initial use stages. This paper contains extensive reference analysis and found a firm background for a new sensor request. The research covers the electric and mechanical properties of the developed sensor and possible future applications.

Single-walled carbon nanotube based coating modified with reduced graphene oxide for the design of amperometric biosensors.

In this study a polycarbonate filter membrane (PcFM) with 400 nm diameter holes was covered/protruded by single walled carbon nanotubes (SWCNT) and then formed PcFM/SWCNT structure was covered by thin layer of graphene oxide (GO) or reduced graphene oxide (rGO) in order to get the multilayered PcFM/SWCNT/GO and PcFM/SWCNT/rGO coatings, respectively. It was determined that the SWCNTs filaments were able to form a layer on the polycarbonate membrane having a number of carbon nanotube arranged in different orientations. A fraction of SWCNT filaments protruded through the holes of polycarbonate membrane and in such way significantly enhanced the adhesion of SWCNT-based layer and provided electrical conductivity across the PcFM. Atomic force microscopy (AFM), scanning electron microscopy (SEM) images and Raman spectroscopy-based evaluation revealed the characteristic morphology features: wide distribution of height profile, separate GO/rGO flakes on the top of PcFM/SWCNT/GO structure and close attachment of rGO flakes on the top of multilayered PcFM/SWCNT/rGO coating. Performed contact angle measurement (CAM) enabled to determine the surface energy components and wettability data of prepared coatings. Both PcFM/SWCNT/GO and PcFM/SWCNT/rGO coatings were modified with glucose oxidase (GOx). Amperometric measurements revealed that multilayered PcFM/SWCNT/rGO/GOx coating is the most suitable structure for glucose biosensor design.