Showing papers by "Tushar Kanti Bera published in 2017"

Electrical Impedance Variations in Banana Ripening: An Analytical Study with Electrical Impedance Spectroscopy

Abstract: Fruit ripening is a very crucial event in food engineering as the fruits are very important and essential food materials for human health. Under-ripening and over-ripening both are not desirable to have all the essential and important nutrients in the fruits which are only available at their optimum-ripening state. Hence, studying the ripening process of fruits is very much essential which will not only help the people to have the best fruit quality but also will help the researcher and scientist to analyze the food quality. Chemical and biochemical analyses conducted to analyze the fruit ripening are time-consuming and destructive in nature; hence, these methods, generally, are not found suitable for routine, fast and repetitive inspections. A fast and nondestructive fruit ripening characterization method is found essential to study the ripening state and fruit nutrients levels. In this direction, the EIS studies have been conducted as a nondestructive evaluation method to study the electrical impedance variations during banana ripening. The electrical impedance of banana samples is measured by Agilent 4294A impedance analyzer at different states of ripening and the ripening states are correlated with their corresponding impedances. All the impedance parameters, Z, phase angle, real part of Z and imaginary part of Z are studied to analyze the ripening phenomena in terms of banana impedance. The results demonstrate that the complex impedance, real part and imaginary part of the impedance all increase with the progresses in the ripening process. Equivalent circuit modeling shows that the ripened banana contains constant phase elements. Statistical analysis conducted on the samples from a same bunch also shows that the electrical impedance spectroscopy technique can be applied for noninvasive characterization of banana ripening. Practical Applications EIS conducted on banana ripening characterizes the banana ripening process in terms of its impedance variation and develops the equivalent circuit. EIS studies establish the correlation between the bioimpedance variation and ripening states which can be potentially utilized to study the banana ripening noninvasively. Statistical analysis shows that the standard deviation of all the impedance parameters of different banana samples obtained from a same bunch is very low compared to the corresponding mean values. It is observed that the EIS study conducted on one banana sample can represent the ripening state of the other bananas and hence the EIS studies conducted on limited number of samples can be utilized to characterize the ripening of the entire banana stacks. Thus EIS studies on banana ripening not only help us to find the optimum ripening state but also it will help the researchers to analyze its physiological changes, taste, and nutrient levels.

Electrical impedance spectroscopic study of mandarin orange during ripening

Abstract: Electrical impedance spectroscopy (EIS) as non-destructive investigation has been conducted to study the electrical impedance variations during ripening of mandarin orange The objective of the work is to study the electrical impedance variations and variations in weight of the orange fruit with different ripening state Electrical equivalent circuit has been modeled relative to the Nyquist plot obtained during the ripening of orange by non-linear curve fitting technique EIS studies on orange fruit have been conducted by applying a small amount of alternating current through an array of Ag/AgCl electrodes attached to the orange fruit The impedance and phase angles of orange fruit are measured at frequency sweep from 50 Hz to 1 MHz for 100 frequency points The results revealed that the impedance, real part and imaginary part of the impedance all are increased and the weight of orange are decreased with the increase in ripening state It is observed that the electrical equivalent circuit of orange fruit contains a constant phase element

Leveraging a temperature-tunable, scale-like microstructure to produce multimodal, supersensitive sensors.

Abstract: The microstructure of a flexible film plays an important role in its sensing capability. Here, we fabricate a temperature-dependent wrinkled single-walled carbon nanotube (SWCNT)/polydimethyl-siloxane (PDMS) film (WSPF) and a wrinkle-dependent scale-like SWCNT/PDMS film (SSPF) successfully, and address the formation and evolution mechanisms of each film. The low elastic modulus and high coefficient of thermal expansion of the PDMS layer combined with the excellent piezoresistive behavior of the SWCNT film motivated us to investigate how the scale-like microstructure of the SSPF could be used to design multimodal-sensing devices with outstanding capabilities. The results show that SSPFs present supersensitive performance in mechanical loading (an effective sensitivity of up to 740.7 kPa−1) and in temperature (a tunable thermal index of up to 29.9 × 103 K). These exceptional properties were demonstrated in practical applications in a programmable flexile pressure sensor, thermal/light monitor or switch, etc., and were further explained through the macroscopic and microscopic piezoresistive behaviors of scale-like SWCNT coatings.

Combining the converse humidity/resistance response behaviors of rGO films for flexible logic devices

Abstract: Carbon nanomaterials have excellent humidity sensing performance. Here, we demonstrate that reduced graphene oxide (rGO)-based conductive films with different thermal reduction times have gradient and invertible humidity/electrical resistance responses: rGO films ( 13 h, negative response, regarded as a signal of “1”). We propose a new mechanism that describes a “scale”-like model for rGO films to explain these behaviors based on contributions from Ohm-contact resistance and capacitive reactance at interplate junctions, and intrinsic resistances of the nanoplates, respectively. This mechanism is accordingly validated via a series of experiments and electrical impedance spectroscopies, which complement more classical models based on proton conductivity. To explore the practical applications of the converse humidity/resistance responses, three simple flexible logic devices were developed, (i) a rGO pattern for a humidity-insensitive conductive film, which has the potential to greatly improve the stability of the carbon-based electrical device to humidity; (ii) a Janus pattern of rGO films for gesture recognition, which is very useful to human/machine interactions; (iii) a sandwich pattern of rGO films for 3-dimensional (3D) noncontact sensing, which will be complementary to the existing 3D touch technique.

Design considerations and performance of a variable gain, variable bandwidth signal processing circuit for acoustoelectric imaging

Abstract: Acoustoelectric (AE) imaging is a new technique for mapping current densities in the heart and brain at a high resolution determined by the size of the ultrasound (US) focus. Because the amplitude of the AE interaction signal in biological tissue is weak (on order of 1 μV), detection of small currents is challenging with poor signal-to-noise ratio (SNR). Because optimal detection depends on minimizing background noise, the design and performance of the recording system, especially amplifiers and filters, is crucial for efficient and sensitive AE imaging. The amplitude and bandwidth of the AE signal depends on a variety of factors, including the US bandwidth and beam pattern, distribution of current densities, properties of the recording electrodes, and amount of averaging/sampling. The primary goal of this work was to optimize the design and performance of the acoustoelectric differential amplifier, including signal processing circuits, to minimize noise and maximize sensitivity for detection of the AE signal. Variable gain, band-pass filter (BPF) cutoffs, and bandwidth are critical design parameters for optimizing the AE imaging platform for mapping weak electric currents in tissue.