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19 pages, 9551 KiB

Open AccessArticle

Flexible Electromagnetic Sensor with Inkjet-Printed Silver Nanoparticles on PET Substrate for Chemical and Biomedical Applications

by Muhammad Usman Ejaz, Tayyaba Irum, Muhammad Qamar and Akram Alomainy

Sensors 2024, 24(20), 6526; https://doi.org/10.3390/s24206526 - 10 Oct 2024

Cited by 1 | Viewed by 1427

Abstract

For this article, a low-cost, compact, and flexible inkjet-printed electromagnetic sensor was investigated for its chemical and biomedical applications. The investigated sensor design was used to estimate variations in the concentration of chemicals (ethanol and methanol) and biochemicals (hydrocortisone—a chemical derivative of cortisol, [...] Read more.

For this article, a low-cost, compact, and flexible inkjet-printed electromagnetic sensor was investigated for its chemical and biomedical applications. The investigated sensor design was used to estimate variations in the concentration of chemicals (ethanol and methanol) and biochemicals (hydrocortisone—a chemical derivative of cortisol, a biomarker of stress and cardiovascular effects). The proposed design’s sensitivity was further improved by carefully choosing the frequency range (0.5–4 GHz), so that the analyzed samples showed approximately linear variations in their dielectric properties. The dielectric properties were measured using a vector network analyzer (VNA) and an Agilent 85070E Dielectric Probe Kit. The sensor design had a resonant frequency at 2.2 GHz when investigated without samples, and a consistent shift in resonant frequency was observed, with variation in the concentrations of the investigated chemicals. The sensitivity of the designed sensor is decent and is comparable to its non-flexible counterparts. Furthermore, the simulation and measured results were in agreement and were comparable to similar investigated sensor prototypes based on non-flexible Rogers substrates (Rogers RO4003C) and Rogers Droid/RT 5880), demonstrating true potential for chemical, biomedical applications, and healthcare. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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13 pages, 4894 KiB

Open AccessArticle

Self-Assembled TiN-Metal Nanocomposites Integrated on Flexible Mica Substrates towards Flexible Devices

by Juncheng Liu, Yizhi Zhang, Hongyi Dou, Benson Kunhung Tsai, Abhijeet Choudhury and Haiyan Wang

Sensors 2024, 24(15), 4863; https://doi.org/10.3390/s24154863 - 26 Jul 2024

Viewed by 948

Abstract

The integration of nanocomposite thin films with combined multifunctionalities on flexible substrates is desired for flexible device design and applications. For example, combined plasmonic and magnetic properties could lead to unique optical switchable magnetic devices and sensors. In this work, a multiphase TiN-Au-Ni [...] Read more.

The integration of nanocomposite thin films with combined multifunctionalities on flexible substrates is desired for flexible device design and applications. For example, combined plasmonic and magnetic properties could lead to unique optical switchable magnetic devices and sensors. In this work, a multiphase TiN-Au-Ni nanocomposite system with core–shell-like Au-Ni nanopillars embedded in a TiN matrix has been demonstrated on flexible mica substrates. The three-phase nanocomposite film has been compared with its single metal nanocomposite counterparts, i.e., TiN-Au and TiN-Ni. Magnetic measurement results suggest that both TiN-Au-Ni/mica and TiN-Ni/mica present room-temperature ferromagnetic property. Tunable plasmonic property has been achieved by varying the metallic component of the nanocomposite films. The cyclic bending test was performed to verify the property reliability of the flexible nanocomposite thin films upon bending. This work opens a new path for integrating complex nitride-based nanocomposite designs on mica towards multifunctional flexible nanodevice applications. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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Conceptual drawing of the design of the work. TiN-based nanocomposite films with plasmonic Au pillars and ferromagnetic Ni pillars as well as core–shell-like pillars demonstrated on flexible mica substrates. Full article ">Figure 2
XRD results of the TiN-Ni/mica, TiN-Au/mica, and TiN-Au-Ni/mica films. * stands for mica (001) peaks. Full article ">Figure 3
Schematic drawings and cross-sectional STEM image as well as the corresponding EDS mappings for (a) TiN-Au/mica and (b) TiN-Ni/mica films. Full article ">Figure 4
(a) Schematic drawing of TiN-Au-Ni/mica film. (b) Cross-sectional STEM image with (c–f) corresponding EDS mappings. (g) Cross-sectional TEM image. (h) Plan-view TEM image. (i) Plan-view STEM image, with (j–m) corresponding EDS mappings. Full article ">Figure 5
IP and OP M-H curves for the (a) TiN-Au-Ni/mica and (b) TiN-Ni/mica film. (c) IP and (d) OP M-H curves for the TiN-Au-Ni/mica film after the bending test. Full article ">Figure 6
(a) IP and (b) OP real permittivity of the TiN-Au/mica, TiN-Ni/mica, and TiN-Au-Ni/mica films. (c) Transmittance of the three films. (d) Transmittance of the TiN-Au-Ni/mica film at different bending statuses. Full article ">Figure 7
Proposed device on a magnetic field enhancing the Raman signal using the TiN-Au-Ni VANs on mica. Full article ">

11 pages, 3136 KiB

Open AccessArticle

Understanding Diffusion in a Single-Metal Organic Framework Crystal Used for Sensing Applications

by Surya Cheemalapati, Karthik Konnaiyan, Yao Chen, Shengqian Ma and Anna Pyayt

Sensors 2024, 24(12), 3842; https://doi.org/10.3390/s24123842 - 14 Jun 2024

Viewed by 1084

Abstract

Metal–organic frameworks (MOFs) stand out as remarkable materials renowned for their exceptionally high surface area and large number of pores, making them invaluable for diverse sensing applications including gas, biomedical, chemical, and optical sensing. Traditional methods of molecule infusion and release often involve [...] Read more.

Metal–organic frameworks (MOFs) stand out as remarkable materials renowned for their exceptionally high surface area and large number of pores, making them invaluable for diverse sensing applications including gas, biomedical, chemical, and optical sensing. Traditional methods of molecule infusion and release often involve a large number of crystals with varying shapes and sizes, leading to averaged outcomes across a heterogeneous crystal population. In this study, we present continuous monitoring of the infusion and release dynamics of model drug molecules, specifically vitamin B₁₂, within individual Tb-mesoMOF crystals. Our findings underscore the critical influence of crystal size and shape on the infusion and diffusion processes and corresponding color change, underscoring the necessity to account for these factors in the design of large-scale systems. Leveraging optical microscopy, we employed a histogram-based algorithm for image processing, enabling automated tracking of diffusion phenomena. This investigation offers crucial insights into the dynamics of these processes, laying the groundwork for optimizing parameters in future sensing systems. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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First step in image processing. Image (b) at is subtracted from initial image (a) to produce the differential image (c). Full article ">Figure 2
Step 2 in image processing where RGB values of subtracted images are extracted. Full article ">Figure 3
Optical and SEM characterization images of individual crystals of Tb-mesoMOF before infusion with vitamin B12: (a) Optical microscope image of the MOF; (b) SEM image of MOF and (c,d) are higher magnification parts of the crystal shown in (b). Full article ">Figure 4
Optical microscopy and SEM characterization of vitamin B12 uptake in Tb-mesoMOF: (a) Optical microscope image of a crystal infused with vitamin B12 for a short period of time; (b) corresponding SEM image of the same crystal in the same orientation as in the optical microscopy image. Full article ">Figure 5
Optical microscopy monitoring of dynamics of molecular vitamin B12 uptake by individual Tb-mesoMOF crystals. (Ia,IIa,IIIa) are schematic representations of microscopy images taken at 20 min (Ib), 60 min (IIb), and 300 min (IIIb), respectively, and (IV) is an image taken at 780 min, during the final stages of uptake. Full article ">Figure 6
Optical microscopy monitoring of dynamics of molecular vitamin B12 uptake by individual Tb-mesoMOF crystals. Image (Ia,Ib) show uncut samples of MOF infused with vitamin B12 for 10 min. (IIa) shows uncut, and (IIb) shows cut MOF crystals infused with vitamin B12 for 20 min. (IIIa) shows uncut, and (IIIb) shows cut MOF crystals infused with vitamin B12 for 180 min. Here, the MOF looks red from outside, but the cut sample shows there is still vacant MOF. (IVa) shows uncut and (IVb) cut MOF crystals infused with vitamin B12 for 780 min. Here, the MOF is completely infused. Full article ">Figure 7
Optical microscopy characterization of vitamin B12 release from an individual Tb-mesoMOF crystal. Images of the crystal infused with vitamin B12 suspended in methanol, and vitamin B12 diffusion out of the crystal at times (a) t = 15 min, (b) t= 30 min, (c) t = 60 min, (d) t = 100 min, (e) t = 200 min, (f) t = 300 min, (g) t = 500 min, (h) t = 1000 min, (i) 1600 min, (j) t = 2350 min, (k) t = 5000 min, and (l) t = 7000 min; (m) a plot demonstrating speed of release of the vitamin B12 vs. time. Full article ">

13 pages, 7223 KiB

Open AccessArticle

Graphene Nanoplatelets/Polydimethylsiloxane Flexible Strain Sensor with Improved Sandwich Structure

by Junshu Zhang, Ke Gao, Shun Weng and Hongping Zhu

Sensors 2024, 24(9), 2856; https://doi.org/10.3390/s24092856 - 30 Apr 2024

Cited by 5 | Viewed by 1704

Abstract

In engineering measurements, metal foil strain gauges suffer from a limited range and low sensitivity, necessitating the development of flexible sensors to fill the gap. This paper presents a flexible, high-performance piezoresistive sensor using a composite consisting of graphene nanoplatelets (GNPs) and polydimethylsiloxane [...] Read more.

In engineering measurements, metal foil strain gauges suffer from a limited range and low sensitivity, necessitating the development of flexible sensors to fill the gap. This paper presents a flexible, high-performance piezoresistive sensor using a composite consisting of graphene nanoplatelets (GNPs) and polydimethylsiloxane (PDMS). The proposed sensor demonstrated a significantly wider range (97%) and higher gauge factor (GF) (6.3), effectively addressing the shortcomings of traditional strain gauges. The microstructure of the GNPs/PDMS composite was observed using a scanning electron microscope, and the distribution of the conductive network was analyzed. The mechanical behavior of the sensor encapsulation was analyzed, leading to the determination of the mechanisms influencing encapsulation. Experiments based on a standard equal-strength beam were conducted to investigate the influence of the base and coating dimensions of the sensor. The results indicated that reducing the base thickness and increasing the coating length both contributed to the enhancement of the sensor’s performance. These findings provide valuable guidance for future development and design of flexible sensors. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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20 pages, 5895 KiB

Open AccessArticle

Fabrications of the Flexible Non-Enzymatic Glucose Sensors Using Au-CuO-rGO and Au-CuO-rGO-MWCNTs Nanocomposites as Carriers

by Shu-Han Liao, Kai-Yi Shiau, Fang-Hsing Wang and Cheng-Fu Yang

Sensors 2023, 23(19), 8029; https://doi.org/10.3390/s23198029 - 22 Sep 2023

Cited by 6 | Viewed by 1689

Abstract

A flexible, non-enzymatic glucose sensor was developed and tested on a polyethylene terephthalate (PET) substrate. The sensor’s design involved printing Ag (silver) as the electrode and utilizing mixtures of either gold–copper oxide-modified reduced graphene oxide (Au-CuO-rGO) or gold–copper oxide-modified reduced graphene oxide-multi-walled carbon [...] Read more.

A flexible, non-enzymatic glucose sensor was developed and tested on a polyethylene terephthalate (PET) substrate. The sensor’s design involved printing Ag (silver) as the electrode and utilizing mixtures of either gold–copper oxide-modified reduced graphene oxide (Au-CuO-rGO) or gold–copper oxide-modified reduced graphene oxide-multi-walled carbon nanotubes (Au-CuO-rGO-MWCNTs) as the carrier materials. A one-pot synthesis method was employed to create a nanocomposite material, consisting of Au-CuO-rGO mixtures, which was then printed onto pre-prepared flexible electrodes. The impact of different weight ratios of MWCNTs (0~75 wt%) as a substitute for rGO was also investigated on the sensing characteristics of Au-CuO-rGO-MWCNTs glucose sensors. The fabricated electrodes underwent various material analyses, and their sensing properties for glucose in a glucose solution were measured using linear sweep voltammetry (LSV). The LSV measurement results showed that increasing the proportion of MWCNTs improved the sensor’s sensitivity for detecting low concentrations of glucose. However, it also led to a significant decrease in the upper detection limit for high-glucose concentrations. Remarkably, the research findings revealed that the electrode containing 60 wt% MWCNTs demonstrated excellent sensitivity and stability in detecting low concentrations of glucose. At the lowest concentration of 0.1 μM glucose, the nanocomposites with 75 wt% MWCNTs showed the highest oxidation peak current, approximately 5.9 μA. On the other hand, the electrode without addition of MWCNTs displayed the highest detection limit (approximately 1 mM) and an oxidation peak current of about 8.1 μA at 1 mM of glucose concentration. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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17 pages, 8837 KiB

Open AccessArticle

Synthesis of ZnO Nanoflower Arrays on a Protrusion Sapphire Substrate and Application of Al-Decorated ZnO Nanoflower Matrix in Gas Sensors

by Xin Zhao, Jang-Cheng Jheng, Ni-Ni Chou, Fang-Hsing Wang and Cheng-Fu Yang

Sensors 2023, 23(12), 5629; https://doi.org/10.3390/s23125629 - 16 Jun 2023

Cited by 3 | Viewed by 1484

Abstract

In this study, we utilized a sapphire substrate with a matrix protrusion structure as a template. We employed a ZnO gel as a precursor and deposited it onto the substrate using the spin coating method. After undergoing six cycles of deposition and baking, [...] Read more.

In this study, we utilized a sapphire substrate with a matrix protrusion structure as a template. We employed a ZnO gel as a precursor and deposited it onto the substrate using the spin coating method. After undergoing six cycles of deposition and baking, a ZnO seed layer with a thickness of 170 nm was formed. Subsequently, we used a hydrothermal method to grow ZnO nanorods (NRs) on the aforementioned ZnO seed layer for different durations. ZnO NRs exhibited a uniform outward growth rate in various directions, resulting in a hexagonal and floral morphology when observed from above. This morphology was particularly evident in ZnO NRs synthesized for 30 and 45 min. Due to the protrusion structure of ZnO seed layer, the resulting ZnO nanorods (NRs) displayed a floral and matrix morphology on the protrusion ZnO seed layer. To further enhance their properties, we utilized Al nanomaterial to decorate the ZnO nanoflower matrix (NFM) using a deposition method. Subsequently, we fabricated devices using both undecorated and Al-decorated ZnO NFMs and deposited an upper electrode using an interdigital mask. We then compared the gas-sensing performance of these two types of sensors towards CO and H₂ gases. The research findings indicate that sensors based on Al-decorated ZnO NFM exhibit superior gas-sensing properties compared to undecorated ZnO NFM for both CO and H₂ gases. These Al-decorated sensors demonstrate faster response times and higher response rates during the sensing processes. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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19 pages, 5252 KiB

Open AccessArticle

Investigating the Electromechanical Sensitivity of Carbon-Nanotube-Coated Microfibers

by Elizabeth Bellott, Yushan Li, Connor Gunter, Scott Kovaleski and Matthew R. Maschmann

Sensors 2023, 23(11), 5190; https://doi.org/10.3390/s23115190 - 30 May 2023

Viewed by 1485

Abstract

The piezoresistance of carbon nanotube (CNT)-coated microfibers is examined using diametric compression. Diverse CNT forest morphologies were studied by changing the CNT length, diameter, and areal density via synthesis time and fiber surface treatment prior to CNT synthesis. Large-diameter (30–60 nm) and relatively [...] Read more.

The piezoresistance of carbon nanotube (CNT)-coated microfibers is examined using diametric compression. Diverse CNT forest morphologies were studied by changing the CNT length, diameter, and areal density via synthesis time and fiber surface treatment prior to CNT synthesis. Large-diameter (30–60 nm) and relatively low-density CNTs were synthesized on as-received glass fibers. Small-diameter (5–30 nm) and-high density CNTs were synthesized on glass fibers coated with 10 nm of alumina. The CNT length was controlled by adjusting synthesis time. Electromechanical compression was performed by measuring the electrical resistance in the axial direction during diametric compression. Gauge factors exceeding three were measured for small-diameter (<25 μm) coated fibers, corresponding to as much as 35% resistance change per micrometer of compression. The gauge factor for high-density, small-diameter CNT forests was generally greater than those for low-density, large-diameter forests. A finite element simulation shows that the piezoresistive response originates from both the contact resistance and intrinsic resistance of the forest itself. The change in contact and intrinsic resistance are balanced for relatively short CNT forests, while the response is dominated by CNT electrode contact resistance for taller CNT forests. These results are expected to guide the design of piezoresistive flow and tactile sensors. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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13 pages, 5057 KiB

Open AccessArticle

The Accumulation of Electrical Energy Due to the Quantum-Dimensional Effects and Quantum Amplification of Sensor Sensitivity in a Nanoporous SiO₂ Matrix Filled with Synthetic Fulvic Acid

by Vitalii Maksymych, Dariusz Calus, Bohdan Seredyuk, Glib Baryshnikov, Rostislav Galagan, Valentina Litvin, Sławomir Bujnowski, Piotr Domanowski, Piotr Chabecki and Fedir Ivashchyshyn

Sensors 2023, 23(8), 4161; https://doi.org/10.3390/s23084161 - 21 Apr 2023

Viewed by 1689

Abstract

A heterostructured nanocomposite MCM-41<SFA> was formed using the encapsulation method, where a silicon dioxide matrix—MCM-41 was the host matrix and synthetic fulvic acid was the organic guest. Using the method of nitrogen sorption/desorption, a high degree of monoporosity in the studied matrix was [...] Read more.

A heterostructured nanocomposite MCM-41<SFA> was formed using the encapsulation method, where a silicon dioxide matrix—MCM-41 was the host matrix and synthetic fulvic acid was the organic guest. Using the method of nitrogen sorption/desorption, a high degree of monoporosity in the studied matrix was established, with a maximum for the distribution of its pores with radii of 1.42 nm. According to the results of an X-ray structural analysis, both the matrix and the encapsulate were characterized by an amorphous structure, and the absence of a manifestation of the guest component could be caused by its nanodispersity. The electrical, conductive, and polarization properties of the encapsulate were studied with impedance spectroscopy. The nature of the changes in the frequency behavior of the impedance, dielectric permittivity, and tangent of the dielectric loss angle under normal conditions, in a constant magnetic field, and under illumination, was established. The obtained results indicated the manifestation of photo- and magneto-resistive and capacitive effects. In the studied encapsulate, the combination of a high value of ε and a value of the tgδ of less than 1 in the low-frequency range was achieved, which is a prerequisite for the realization of a quantum electric energy storage device. A confirmation of the possibility of accumulating an electric charge was obtained by measuring the I-V characteristic, which took on a hysteresis behavior. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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13 pages, 5394 KiB

Open AccessEditor’s ChoiceArticle

The 0-3 Lead Zirconate-Titanate (PZT)/Polyvinyl-Butyral (PVB) Composite for Tactile Sensing

by Eun-Bee Jo, Yoon-A Lee, Yoon-A Cho, Paul A. Günther, Sylvia E. Gebhardt, Holger Neubert and Hyun-Seok Kim

Sensors 2023, 23(3), 1649; https://doi.org/10.3390/s23031649 - 2 Feb 2023

Cited by 7 | Viewed by 3253

Abstract

In this study, a 0-3 piezoelectric composite based on lead zirconate-titanate (PZT)/polyvinyl-butyral (PVB) was fabricated and characterized for its potential application in tactile sensing. The 0-3 composite was developed to incorporate the advantages of both ceramic and polymer. The paste of 0-3 PZT–PVB [...] Read more.

In this study, a 0-3 piezoelectric composite based on lead zirconate-titanate (PZT)/polyvinyl-butyral (PVB) was fabricated and characterized for its potential application in tactile sensing. The 0-3 composite was developed to incorporate the advantages of both ceramic and polymer. The paste of 0-3 PZT–PVB composite was printed using a conventional screen-printing technique on alumina and mylar substrates. The thickness of the prepared composite was approximately 80 μm. After printing the top electrode of the silver paste, 10 kV/mm of DC field was applied at 25 °C, 120 °C, and 150 °C for 10 min to align the electric dipoles in the composite. The piezoelectric charge coefficient of

d_{33}

and the piezoelectric voltage coefficient of

g_{33}

were improved by increasing the temperature of the poling process. The maximum values of

d_{33}

and

g_{33}

were 14.3 pC/N and 44.2 mV·m/N, respectively, at 150 °C. The sensor’s sensitivity to the impact force was measured by a ball drop test. The sensors showed a linear behavior in the output voltage with increasing impact force. The sensitivity of the sensor on the alumina and mylar substrates was 1.368 V/N and 0.815 V/N, respectively. The rising time of the sensor to the finger touch was 43 ms on the alumina substrate and 35 ms on the mylar substrate. Consequently, the high sensitivity and fast response time of the sensor make the 0-3 PZT–PVB composite a good candidate for tactile sensors. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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10 pages, 5050 KiB

Open AccessArticle

Comparison of Characteristics of a ZnO Gas Sensor Using a Low-Dimensional Carbon Allotrope

by Jihoon Lee, Jaebum Park and Jeung-Soo Huh

Sensors 2023, 23(1), 52; https://doi.org/10.3390/s23010052 - 21 Dec 2022

Cited by 1 | Viewed by 1766

Abstract

Owing to the increasing construction of new buildings, the increase in the emission of formaldehyde and volatile organic compounds, which are emitted as indoor air pollutants, is causing adverse effects on the human body, including life-threatening diseases such as cancer. A gas sensor [...] Read more.

Owing to the increasing construction of new buildings, the increase in the emission of formaldehyde and volatile organic compounds, which are emitted as indoor air pollutants, is causing adverse effects on the human body, including life-threatening diseases such as cancer. A gas sensor was fabricated and used to measure and monitor this phenomenon. An alumina substrate with Au, Pt, and Zn layers formed on the electrode was used for the gas sensor fabrication, which was then classified into two types, A and B, representing the graphene spin coating before and after the heat treatment, respectively. Ultrasonication was performed in a 0.01 M aqueous solution, and the variation in the sensing accuracy of the target gas with the operating temperature and conditions was investigated. As a result, compared to the ZnO sensor showing excellent sensing characteristics at 350 °C, it exhibited excellent sensing characteristics even at a low temperature of 150 °C, 200 °C, and 250 °C. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Sensing)

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