Towards Wireless Detection of Surface Modification of Silicon Nanowires by an RF Approach

This paper shows the possibility to detect the presence of grafted molecules on the surface of silicon nanowires with a wireless RF radar approach based on the measurement of the backscattered signal of a resonant structure on which the nanowires are deposited. The measured resonance frequency allows the determination of the intrinsic properties related to temperature and humidity variations, which can be related to the presence of the grafted molecules. Several functionalizations of nanowires have been realized and characterized. For the first time, an RF approach is used to detect significant differences related to the presence of grafted molecules on the surface of nanowires. In addition to detecting their presence, the obtained results show the potential of the radar approach to identify the type of functionalization of nanowires. A set of six different grafted molecules (including octadecyltrichlorosilane, ethynylpyrene, N3) was tested and correctly separated with the proposed approach. Various measurements of the same samples showed a good repeatability which made the approach compatible with the possibility of differentiating the molecules with each other by radar reading. Moreover, discussions about the application of such functionalizations are made to increase the sensibility of sensors using a radar approach.

The Design of Low-Cost Stand-Alone Microcontroller-Based Wireless Ultrasonic System for Process Monitoring and Analysis

OBJECTIVES

Ultrasound technology is currently used in many areas, such as imaging, analysis, and process monitoring. The noninvasive implementation, nondestructive effect on the material to be applied, and low cost of the needed components give an advantage to the ultrasonic systems when compared to other methods for analysis and process monitoring studies. However, the current ultrasonic analysis setups used in the studies require additional devices such as a signal generator and oscilloscope. These devices used in the setup increase the cost, size, usage difficulty of the system and, most importantly, decrease the portability and stability. In order to prevent these disadvantages, an ultrasonic system that can work in real-time and its software are developed to be used in analysis and process monitoring without any additional devices.

METHODS

This system was designed by using a microcontroller. The developed system is portable, has a small size, and a Bluetooth Low Energy connection. It has a battery for using standalone.

RESULTS

Therefore, it can be easily used in different small and closed measurement environments such as incubators and controlled remotely. In addition, a mixture was analyzed with both the designed system and a commercial module. When the results are compared, two systems are found highly correlated r 2 = 1 . CONCLUSION: In this study, an embedded ultrasonic measurement system and its software are developed to be used in analysis studies, density measurements, and real-time process monitoring as a stand-alone device.

Subsurface H2S Detection by a Surface Acoustic Wave Passive Wireless Sensor Interrogated with a Ground Penetrating Radar

Long-term monitoring of organic pollutants in the soil is a major environmental challenge. We propose to meet this issue by the development of a polymer dedicated to selectively react with H₂S, coating surface acoustic wave transducers designed as passive cooperative targets with the compound, and probing their response using Ground Penetrating RADAR, thus providing the capability to monitor the presence of H₂S in the subsurface environment. The selectivity is brought by including lead(II) cation in a reticulated polymer matrix which can be deposited as a thin layer on a surface acoustic wave sensor. We demonstrate a signal enhancement mechanism in which water absorption magnifies the signal detection, making the sensor most sensitive to H₂S in an underground environment saturated with moisture.