Microfabricated electrochemical pH and free chlorine sensors for water quality monitoring: recent advances and research challenges

Qin, Yiheng; Kwon, Hyuck-Jin; Howlader, M. M. R.; Deen, M. Jamal

doi:10.1039/c5ra11291e

Cited by 165 publications

(172 citation statements)

References 184 publications

(251 reference statements)

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“…The integrated sensors exhibit high sensitivity, fast response, good stability, and are highly accurate in measuring real water samples. These low‐cost printed sensors have the potential to be implemented in future wearable and portable electrochemical systems for ubiquitous monitoring of environmental parameters and human health conditions …”

Section: Introductionmentioning

confidence: 99%

“…The Pd inks used in these studies had low metal content (normally <5 wt%), which resulted in very thin, discontinuous, and high‐resistance Pd films. Such Pd films were undesirable for electrochemical sensing because the inefficient electron transfer in the high‐resistance films results in a poor sensing performance . One method to reduce the resistance is to print the lightly loaded ink using multiple passes, but this is time‐consuming .…”

Section: Introductionmentioning

confidence: 99%

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Inkjet Printing of a Highly Loaded Palladium Ink for Integrated, Low‐Cost pH Sensors

Qin

Alam

Howlader

et al. 2016

Adv Funct Materials

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An inkjet printing process for depositing palladium (Pd) thin films from a highly loaded ink (>14 wt%) is reported. The viscosity and surface tension of a Pd-organic precursor solution is adjusted using toluene to form a printable and stable ink. A two-step thermolysis process is developed to convert the printed ink to continuous and uniform Pd films with good adhesion to different substrates. Using only one printing pass, a low electrical resistivity of 2.6 μΩ m of the Pd film is obtained. To demonstrate the electrochemical pH sensing application, the surfaces of the printed Pd films are oxidized for ion-to-electron transduction and the underlying layer is left for electron conduction. Then, solid-state reference electrodes are integrated beside the bifunctional Pd electrodes by inkjet printing. These potentiometric sensors have sensitivities of 60.6 ± 0.1 and 57 ± 0.6 mV pH −1 on glass and polyimide substrates, and short response times of 11 and 6 s, respectively. Also, accurate pH values of real water samples are obtained by using the printed sensors with a low-cost multimeter. These results indicate that the facile and cost-effective inkjet printing and integration techniques may be applied in fabricating future electrochemical monitoring systems for environmental parameters and human health conditions. DOI IntroductionInkjet printing is an easy-to-use and low-cost approach to simultaneously deposit and pattern thin film materials from solutions. This technology can produce structures with fine patterns, consumes a small amount of materials, does not need complicated equipment, and is compatible with largearea processing lines for flexible and non-planar substrates. [1] Numerous applications, for example, high-resolution electrodes, [2,3] field-effect transistors, [4] solar cells, [5] light-emitting devices, [6] bio/chemical sensors, [7] and bio-printed tissues, [8] were enabled by using inkjet printing technology. In these electron transfer in the high-resistance films results in a poor sensing performance. [23] One method to reduce the resistance is to print the lightly loaded ink using multiple passes, but this is time-consuming. [15] Alternatively, highly loaded Pd inks and their inkjet printing processes can be developed to deposit continuous, homogenous, and conductive Pd films using a single print pass, thus making it a fast film deposition technique.In this work, we developed an ink loaded with >14 wt% Pd for inkjet printing. The inkjet printing process for such ink is optimized for the deposition of continuous, uniform and lowresistivity thin films with good adhesion to the underlying substrates. Utilizing this ink and printing process, we demonstrate the practical and cost-effective fabrication of an integrated pH sensing platform on both rigid and flexible substrates. Bifunctional sensing electrodes are fabricated by oxidizing the printed Pd. The PdO-rich surfaces function as pH sensing layers and the conductive portion beneath the surfaces are electron conduction paths. Solid-state reference elec...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inkjet Printing of a Highly Loaded Palladium Ink for Integrated, Low‐Cost pH Sensors

Qin

Alam

Howlader

et al. 2016

Adv Funct Materials

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“…pH sensing has been specifically shown to be of paramount importance in many areas such as environmental science, biological studies, sport, health care, as nature (acid or alkaline) of a solution is a marker of physiological state [1][2][3]. These are very useful in many applications, for instance; testing of water, blood samples, agricultural production, food processing, environmental monitoring etc [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Tantalum oxide thin films for electrochemical pH sensor

Sharma

Kumar

Kumari

et al. 2020

Mater. Res. Express

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Present work demonstrates the fabrication and utilization of tantalum oxide (Ta 2 O 5 ) thin films as prominent pH sensing electrode material. Ta 2 O 5 film of 1 μm thickness was deposited on glass substrates using physical vapor deposition technique. Structural and morphological studies were performed on these thin films. Electrochemical studies were carried out on these films using amperometry, linear sweep voltammetry and cyclic voltammetry techniques. These Ta 2 O 5 coated substrates were found to be sensitive to various assorted pH solutions and hence were used as pH sensing electrode. The performance of the electrode was studied in terms of stability, reusability and selectivity. Results reveal that the films were found to be suitable pH sensing material in 1.0-12.0 pH range. The sensing electrodes were found to be reliable and reusable with less than 5 s response time.

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“…Examples of integrated micro-optical systems have been shown in previous sections. The fabrication and integration cost is the major part of the total product cost [158]. High volume and efficient production may reduce the product cost.…”

Section: Cost Reduction Approachesmentioning

confidence: 99%

Low-Temperature Bonding for Silicon-Based Micro-Optical Systems

Howlader

Deen

2015

Photonics

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Abstract:Silicon-based integrated systems are actively pursued for sensing and imaging applications. A major challenge to realize highly sensitive systems is the integration of electronic, optical, mechanical and fluidic, all on a common platform. Further, the interface quality between the tiny optoelectronic structures and the substrate for alignment and coupling of the signals significantly impacts the system's performance. These systems also have to be low-cost, densely integrated and compatible with current and future mainstream technologies for electronic-photonic integration. To address these issues, proper selection of the fabrication, integration and assembly technologies is needed. In this paper, wafer level bonding with advanced features such as surface activation and passive alignment for vertical electrical interconnections are identified as candidate technologies to integrate different electronics, optical and photonic components. Surface activated bonding, superior to other assembly methods, enables low-temperature nanoscaled component integration with high alignment accuracy, low electrical loss and high transparency of the interface. These features are preferred for the hybrid integration of silicon-based micro-opto-electronic systems. In future, new materials and assembly technologies may emerge to enhance the performance of these micro systems and reduce their cost. The article is a detailed review of bonding techniques for electronic, optical and photonic components in silicon-based systems.

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Microfabricated electrochemical pH and free chlorine sensors for water quality monitoring: recent advances and research challenges

Cited by 165 publications

References 184 publications

Inkjet Printing of a Highly Loaded Palladium Ink for Integrated, Low‐Cost pH Sensors

Inkjet Printing of a Highly Loaded Palladium Ink for Integrated, Low‐Cost pH Sensors

Tantalum oxide thin films for electrochemical pH sensor

Low-Temperature Bonding for Silicon-Based Micro-Optical Systems

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