3D printing has gained significant research interest recently for directly manufacturing 3D components and structures for use in a variety of applications. In this paper, a digital light processing (DLP®) based 3D printing technique was explored to manufacture electrically conductive objects of polymer nanocomposites. Here, the ink was made of a mixture of photocurable resin with multi-walled carbon nanotubes (MWCNTs). The concentrations of MWCNT as well as the printing parameters were investigated to yield optimal conductivity and printing quality. We found that 0.3 wt% loading of MWCNT in the resin matrix can provide the maximum electrical conductivity of 0.027S/m under the resin viscosity limit that allows high printing quality. With electric conductivity, the printed MWCNT nanocomposites can be used as smart materials and structures with strain sensitivity and shape memory effect. We demonstrate that the printed conductive complex structures as hollow capacitive sensor, electrically activated shape memory composites, stretchable circuits, showing the versatility of DLP® 3D printing for conductive complex structures. In addition, mechanical tests showed that the addition of MWCNT could slightly increase the modulus and ultimate tensile stress while decreasing slightly the ultimate stretch, indicating that the new functionality is not obtained at the price of sacrificing mechanical properties.

Digital light processing 3D printing of conductive complex structures

Water level sensing: State of the art review and performance evaluation of a low-cost measurement system

Fibre Bragg grating (FBG) pressure sensors show a great potential in replacing conventional electrical pressure sensors due to their numerous advantages. However, increasing their pressure sensitivity performance for low hydrostatic pressure measurement is still a challenge. This paper reviewed recent pressure sensitivity enhancement methods that could be divided into two groups, namely intrinsic and extrinsic. For the intrinsic enhancement method, this paper reviewed polymer FBGs, special fibre sensors, interferometric sensors, and special grating sensors. For the extrinsic enhancement method, polymer-based pressure transducers, diaphragm-based pressure transducers, and other structure-based pressure transducers were reviewed in detail.

Review of high sensitivity fibre-optic pressure sensors for low pressure sensing

The capacitive sensors are used in a variety of industrial and automotive application. A capacitive sensor converts a change in position, or properties of dielectric material into an electrical sig...

https://journals.sagepub.com/doi/pdf/10.1177/0020294014546943

A Review on Capacitive-Type Sensor for Measurement of Height of Liquid Level

Towards self-powered sensing using nanogenerators for automotive systems

The conventional capacitance-type liquid level sensor consists of an insulated solid metallic rod electrode immersed in the liquid contained in a metallic storage tank, or two such identical electrodes in a nonmetallic storage tank. Such metallic rods may suffer from the self-inductance effect which varies nonlinearly with the level. In this paper, we present a modified capacitance-type level sensor in which effect of self-inductance of the metallic rod has been eliminated. The theoretical equations describing the operation of the sensor are derived. The sensor is designed and tested experimentally and is found to follow the theoretical equations. The experimental results are also presented. A very good linearity of the sensor is observed.

Study of a Modified Capacitance-Type Level Transducer for Any Type of Liquid

In the present work, a noninvasive technique of glucose concentration measurement in human blood has been developed. A semicylindrical capacitive sensor is used to measure the blood glucose concentration in terms of capacitance of the sensor. It is shown that this capacitance varies linearly with glucose concentration in human blood. A low frequency operational amplifier based circuit is designed to measure this capacitance in terms of an output voltage signal. A linear relation between the ratio of this output signal to input supply with blood glucose concentration is derived in the paper. A microcontroller based software program is designed to measure this ratio and to display glucose concentration in a LCD display unit in digital form. The performance study of the proposed blood glucose concentration measurement circuit with respect to standard glucometer and that of the proposed blood glucose concentration display unit are carried out in the present work. The experimental results are reported in the paper in both tabular and graphical forms. The linear characteristic graphs and close conformity of the results of the proposed technique with those of standard glucometer are observed. The measurement error with respect to glucometer is found to be within ±3.5%.

A non-invasive microcontroller based estimation of blood glucose concentration by using a modified capacitive sensor at low frequency

The fluid flow rate through a pipeline is a very important process variable in any process plant that is required to be measured accurately. In this article, a new noncontact semicylindrical capacitive flow sensing technique has been developed and studied. The proposed capacitive sensor consists of two semicylindrical curved copper plates mounted on the outside surface of an insulating pipeline near the turbulence region produced at the junction of a larger diameter pipe and a smaller diameter pipe. Here the insulating pipeline section between the copper plates along with the flowing fluid acts as a composite dielectric material of the sensing capacitor. The semicylindrical curved copper plates along with two lead wires are rigidly mounted without any air gap on the larger diameter pipe using a thin layer of araldite. A mathematical relation between the sensor capacitance and flow rate is derived in this article. This capacitance is found to vary nonlinearly with flow rate and is measured using an op-amp-based DeSauty bridge-type transducer circuit where a similar capacitor with the same fluid at zero flow is used as a dummy capacitor. A prototype unit of the proposed transducer is designed, developed and tested experimentally. The static characteristic curves drawn from the experimental results are found to follow the derived mathematical equation to a very good extent with good repeatability.

Abhinaba Dutta

Papers

Study of a Modified Capacitance-Type Level Transducer for Any Type of Liquid

A non-invasive microcontroller based estimation of blood glucose concentration by using a modified capacitive sensor at low frequency

Study of a Noncontact Flow Transducer Using Semicylindrical Capacitive Sensor