Microstrip Resonant Sensor for Differentiation of Components in Vapor Mixtures

Abstract

A novel microstrip resonant vapor sensor made from a conductive multiwalled carbon nanotubes/ethylene-octene copolymer composite, of which its sensing properties were distinctively altered by vapor polarity, was developed for the detection of organic vapors. The alteration resulted from the modified composite electronic impedance due to the penetration of the vapors into the copolymer matrix, which subsequently swelled, increased the distances between the carbon nanotubes, and disrupted the conducting paths. This in turn modified the reflection coefficient frequency spectra. Since both the spectra and magnitudes of the reflection coefficients at the resonant frequencies of tested vapors were distinct, a combination of these parameters was used to identify the occurrence of a particular vapor or to differentiate components of vapor mixtures. Thus, one multivariate MWCNT/copolymer microstrip resonant sensor superseded an array of selective sensors.

Ammonia plasma-treated carbon nanotube/epoxy composites and their using in sensing applications

“…The sensing mechanism of the sensor was based on changes in its reflection coefficient, which indicates how much of an electromagnetic wave is reflected by MWCNT-Epoxy microstrip impedance affected by VOC adsorption. Details on the initial design and original use of microstrip resonant vapor sensors with microstrips made of thermoplastic ethyleneoctene copolymer matrix and embedded MWCNTs are given in our recent paper [58]. The schematic and the photo in Figure 11 shows how the MWCNT-Epoxy composite strip (40×8 mm and thickness of 2.5 mm) and was attached to a dielectric poly(methyl methacrylate) plate (Polycasa, s.r.o., Pribram, Czech Republic) of 60×70 mm and thickness of 1.5 mm.…”

“…After exposure to the given vapor for the predetermined time ensuring complete vapor adsorption into the composite microstrip within 120 s, the power reflected from the sensor was assessed in the range from 2 MHz to 4 GHz by the N9912A FieldFox Handheld RF spectrum analyzer (Keysight Technologies, Santa Rosa, CA, USA) and quantified by the sensor reflection coefficient. The desorption time was also 120 s. Additional details on the measurement procedure used are in our paper [58]. In the initial state prior to vapor exposure, there were three reductions in the reflection coefficient spectrum at frequencies of about 2.85, 3.35,and 3.75 GHz (Figure 12).…”

Biochemical Methanol Gas Sensor (MeOH Bio-Sniffer) for Non-Invasive Assessment of Intestinal Flora from Breath Methanol

“…On the other hand, sensors are expected to be used closer to the site than lab-based analytical devices. Therefore, it is required that sensors be simple to operate and compact in size along with sufficient sensitivity, selectivity, and capability of continuous measurement for some occasions [ 24 , 25 , 26 , 27 , 28 , 29 ]. However, generally, there is a trade-off between being compact in size and having high sensitivity, and it is very challenging to meet both requirements.…”

Fabrication of composited electrode based on coconut activated carbon and MCNTs for ionic electrosorption

“…Xử lý than ống nano đa tường b) MCNTs được trộn với 400 mL H2SO4 0,5 M và 2 g KMnO4. Hỗn hợp được đánh siêu âm trong 30 phút và đun hồi lưu ở 80 °C trong 8 giờ[16]. Sau đó, sản phẩm rắn được tách ra khỏi hỗn hợp bằng cách lọc trên phiểu Buchner, sau đó, ngâm trong dung dịch HCl 1 M ở nhiệt độ phòng 1 giờ để loại bỏ oxit và muối kim loại.…”

“…MCNTs được trung hòa bằng dung dịch NH3 và rửa lại bằng nước cất trong nhiều lần đến khi nước rửa có pH trung tính. MCNTs được làm khô ở 40 °C trong chân không trong 48 giờ [16]. Chế tạo điện cực compositeGA được thêm vào dung dịch PVA 6% trong nước, khuấy từ trong 1 giờ.…”