In-house Developed Sensor Research Articles

A double-sided surface scanning platform for sapphire substrate quality assessment

With excellent mechanical and optical properties, sapphire substrate becomes a very important industrial material especially for LED manufacturing. Its quality control requires two tasks, double-sided surface profiling and defect detection. In this paper, a 3D surface scanning system is proposed as a platform for sapphire substrate inspection. During the scanning process, the height information of both upper and lower surfaces is measured by a chromatic confocal probe. For lateral positioning feedback, an in-house developed sensor, namely, image grating, is introduced in this paper. For these inspection processes, there are three challenges: 1) the motion error in the vertical direction, 2) simultaneous measurement of both upper and lower surfaces, and 3) lateral positioning error in a large scanning area. To address these challenges, three key technologies were developed: 1) real-time motion error compensation based on a fringe interferometer, 2) a double-sided measurement for transparent specimen without the pre-knowledge of its refractive index, and 3) planar image grating pair for accurate 2D displacement feedback. The experimental results showed that the proposed measurement system was able to achieve 50 nm accuracy of the standard deviation when measuring the step height of gauge blocks. When the system measured 4-inch double-sided polished sapphire substrate, the measurement repeatability of TTV (Total Thickness Variation) was within 60 nm; and that of warpage was within 10 nm. As a side product, refractive index can also be measured using the proposed system, and experimental results showed respectable consistency.

Water vapour condensation on the surface of bulky fruit: Some basics and a simple measurement method

In the postharvest chain of fruit and vegetables, temperature fluctuations frequently occur in the surrounding air, which can lead to condensation of water vapour on the surface of fresh produce. Such processes can have a negative impact on the shelf life of horticultural products. Available sensors for measuring condensation phenomena, in particular on the curved surfaces of bulky fruit, are not suitable or can only be used to a very limited extent. The aim of the present study was to measure condensation on curved surfaces of bulky fruit and to evaluate the influence of the process parameters involved. Some fundamental aspects of condensation on the surface of single apples were analysed using the standard methods of condensation measurement that involve the continuous weighing of the product and measuring the dew-point undershoot. In the context of two typical postharvest scenarios, an in-house developed sensor based on the electrical resistance was tested and validated. The wetness sensor allowed reliable determination of the condensation retention time during re-warming and in both uniform and non-uniform temperature fluctuations on apple fruit. While the retention time of condensed water on the fruit surface was successfully measured, only qualitative statements can be made regarding the intensity of the condensation. • Some basic principles of condensation on the surface of bulky fruits have been studied. • Three independent methods were used to measure condensation processes on individual apples. • An in-house developed sensor to determine the retention time of condensed water was tested and validated successfully. . • We measured condensation on fruit surfaces in two typical post-harvest scenarios.

Inkjet-Printed Flexible Temperature Sensor using Hybrid Reduced Graphene Oxide – Silver Nanoparticles(rGO/AgNPs) Conductive Ink and Silver Nanoparticles Ink

This paper presents a new temperature sensor, inkjet-printed with the in-house developed hybrid rGO/Ag nanoparticles ink (rGO/AgNPs ink). Its performance is studied, and the results indicate that its sensitivity is better than the commercial sensor. The meander—shaped electrodes were fabricated using drop-on-demand inkjet printer (Fujifilm Dimatix 2850 printer) on polyethylene terephthalate (PET) substrate. Compared to the sensitivity 0.0543 ?/oc of the sensor developed with commercial ink, the in-house developed sensor shows higher sensitivity 0.1086 ?/oc. Besides, the printed sensors exhibit its resistance increasing linearly with temperature from 30°C to 100°C. The bending tests results also prove that the characteristics of the sensors do not vary significantly, indicating excellent mechanical stability and flexibility. Therefore, the flexible inkjet-printed temperature sensor with the in-house hybrid rGO/AgNPs ink is recommended for the large-scale productions and implementations.

Sensor for Continuous and Real-Time Monitoring of Biomolecule Permeation Through Ultrathin Silicon Nanoporous Membranes

The increase in demand for continuous and real-time monitoring of permeation of biomolecules is addressed by using highly selective ultrathin silicon nanoporous membranes (SNMs) combined with detection using ultraviolet absorption. The membranes, with an average pore size of 8.8 nm, are fabricated using semiconductor batch processes including chemical vapor deposition and rapid thermal annealing. Bovine serum albumin (BSA) of a concentration of $250~\mu \text{g}$ /ml is used as the test molecule. The concentration of BSA diffused through the membrane is measured using optical transduction based in-house developed sensor. The photocurrent obtained from the sensor is measured every 15 min and compared with the standard Bradford assay at the same time-stamp. The concentration estimated by the sensor is found to agree with the Bradford assay with a standard deviation of 1.4%. The throughput of the membrane is increased by fabricating an array of SNMs, which showed an increase in diffusion rate by 3.8 times with respect to the single SNM. The clogging of pores by the biomolecules is analyzed using ionic conductivity experiments. The structural integrity of BSA diffused through the SNM is also analyzed.