One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in polyaniline nanowire-based sensors are summarized. Finally, the current limitations and the future prospect of polyaniline nanowires are discussed.

https://www.mdpi.com/2079-4991/3/3/498/pdf?y=1

Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing

The field of printed wearable electronics has witnessed spectacular growth due to its promise to offer low-cost, high-performance devices for a broad range of applications. Among the sub-fields of printed wearable electronics, printed wearable electrochemical systems are of special importance due to their widespread applications in healthcare, energy and security fields. These systems have opened up new avenues for body-integrated electronics that were earlier impossible to achieve. These include wearable energy systems and sensors for a wide variety of applications. Much of the success of printed wearable electrochemical systems can be attributed to innovations in materials engineering that have led to novel inks comprising of new nanomaterials, polymers and composites. New generation of printed electrochemical devices include soft, stretchable and anatomically-compliant devices that enable efficient bio-integration and withstand high tensile stress associated with on-body applications. Progress in materials science has also led to the development of self-healing printed electrochemical systems for wearable applications. This review provides an overview of the key material requirements for ink formulations for realizing efficient wearable electrochemical systems such as batteries, supercapacitors, biofuel cells and sensors. Finally, major challenges impeding the field of wearable electrochemical systems are discussed along with future prospects of this exciting field.

Advanced Materials for Printed Wearable Electrochemical Devices: A Review

Transparent conducting films (TCFs) are a critical component in many personal electronic devices. Transparent and conductive doped metal oxides are widely used in industry due to their excellent optoelectronic properties as well as the mature understanding of their production and handling. However, they are not compatible with future flexible electronics developments where large-scale production will likely involve roll-to-roll manufacturing. Recent studies have shown that carbon nanotubes provide unique chemical, physical, and optoelectronic properties, making them an important alternative to doped metal oxides. This Review provides a comprehensive analysis of carbon nanotube transparent conductive films covering detailed fabrication methods including patterning of the films, chemical doping effects, and hybridization with other materials. There is a focus on optoelectronic properties of the films and potential in applications such as photovoltaics, touch panels, liquid crystal displays, and organic light-emitting diodes in conjunction with a critical analysis of both the merits and shortcomings of carbon nanotube transparent conductive films.

Recent Development of Carbon Nanotube Transparent Conductive Films

Three decades of nucleic acid aptamer technologies: Lessons learned, progress and opportunities on aptamer development.

Four-dimensional (4D) bioprinting, encompassing a wide range of disciplines including bioengineering, materials science, chemistry, and computer sciences, is emerging as the next-generation biofabrication technology. By utilizing stimuli-responsive materials and advanced three-dimensional (3D) bioprinting strategies, 4D bioprinting aims to create dynamic 3D patterned biological structures that can transform their shapes or behavior under various stimuli. In this review, we highlight the potential use of various stimuli-responsive materials for 4D printing and their extension into biofabrication. We first discuss the state of the art and limitations associated with current 3D printing modalities and their transition into the inclusion of the additional time dimension. We then suggest the potential use of different stimuli-responsive biomaterials as the bioink that may achieve 4D bioprinting where transformation of fabricated biological constructs can be realized. We finally conclude with future perspectives.

https://iopscience.iop.org/article/10.1088/1758-5090/9/1/012001/pdf

4D bioprinting: the next-generation technology for biofabrication enabled by stimuli-responsive materials.

Neurotransmitters are chemicals that act as messengers in the synaptic transmission process. They are essential for human health and any imbalance in their activities can cause serious mental disorders such as Parkinson’s disease, schizophrenia, and Alzheimer’s disease. Hence, monitoring the concentrations of various neurotransmitters is of great importance in studying and diagnosing such mental illnesses. Recently, many researchers have explored the use of unique materials for developing biosensors for both in vivo and ex vivo neurotransmitter detection. A combination of nanomaterials, polymers, and biomolecules were incorporated to implement such sensor devices. For in vivo detection, electrochemical sensing has been commonly applied, with fast-scan cyclic voltammetry being the most promising technique to date, due to the advantages such as easy miniaturization, simple device architecture, and high sensitivity. However, the main challenges for in vivo electrochemical neurotransmitter sensors are limited target selectivity, large background signal and noise, and device fouling and degradation over time. Therefore, achieving simultaneous detection of multiple neurotransmitters in real time with long-term stability remains the focus of research. The purpose of this review paper is to summarize the recently developed sensing techniques with the focus on neurotransmitters as the target analyte, and to discuss the outlook of simultaneous detection of multiple neurotransmitter species. This paper is organized as follows: firstly, the common materials used for developing neurotransmitter sensors are discussed. Secondly, several sensor surface modification approaches to enhance sensing performance are reviewed. Finally, we discuss recent developments in the simultaneous detection capability of multiple neurotransmitters.

Recent Advances in the Detection of Neurotransmitters

In this brief, we consider reactive power and DC voltage tracking control of a three-phase voltage source converter (VSC). This control problem is important in many power system applications including power factor correction for a distribution static synchronous compensator (D-STATCOM). Traditional approaches to this problem are often based on a linearized model of the VSC and proportional-integral (PI) feedback. In order to improve performance, a flatness-based tracking control for the VSC is proposed where the nonlinear model is directly compensated without a linear approximation. Flatness leads to straightforward open-loop control design. A full experimental validation is given as well as a comparison with the industry-standard decoupled vector control. Robustness of the flatness-based control is investigated and setpoint regulation for unbalanced three-phase voltage is considered.

Experimental Validation of Nonlinear Control for a Voltage Source Converter

This paper presents a fully inkjet-printed electrochemical sensor on paper which consists of carbon nanotube-printed working, reference, and counter electrodes. The proposed technique aims at low-cost and disposable paper-based electrochemical sensors. First, a carbon nanotube (CNT) ink was inkjet-printed directly on paper, forming a conductive network. Additionally, a hydrophobic barrier was patterned on paper to limit the absorption of liquid to the designed area. The inkjet printing method allows for rapid patterning of electrodes on paper, resulting in a simple and effective electrochemical sensor. The sheet resistance of the CNT-printed paper was as low as 1 k / after 33 prints. A potential step voltammetry method was applied to determine the concentration of the analytes, iron ion (Fe2+) and dopamine (DA), with linear ranges of 10 μM-200 μM and 10 μM-100 μM, respectively. The reported approach for a fully inkjet-printed electrochemical sensor is easy and cheap, and it has a potential for simple and rapid paper-based point-of-care diagnostics. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0121510jss] All rights reserved.

A Paper-Based Electrochemical Sensor Using Inkjet-Printed Carbon Nanotube Electrodes

Aptamers are oligonucleotides or peptides that are selected from a pool of random sequences that exhibit high affinity toward a specific biomolecular species of interest. Therefore, they are ideal for use as recognition elements and ligands for binding to the target. In recent years, aptamers have gained a great deal of attention in the field of biosensing as the next-generation target receptors that could potentially replace the functions of antibodies. Consequently, it is increasingly becoming popular to integrate aptamers into a variety of sensing platforms to enhance specificity and selectivity in analyte detection. Simultaneously, as the fields of lab-on-a-chip (LOC) technology, point-of-care (POC) diagnostics, and personal medicine become topics of great interest, integration of such aptamer-based sensors with LOC devices are showing promising results as evidenced by the recent growth of literature in this area. The focus of this review article is to highlight the recent progress in aptamer-based biosensor development with emphasis on the integration between aptamers and the various forms of LOC devices including microfluidic chips and paper-based microfluidics. As aptamers are extremely versatile in terms of their utilization in different detection principles, a broad range of techniques are covered including electrochemical, optical, colorimetric, and gravimetric sensing as well as surface acoustics waves and transistor-based detection.

https://www.mdpi.com/2072-666X/11/2/220/pdf

Edward Song

Papers

Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing

Recent Advances in the Detection of Neurotransmitters

Experimental Validation of Nonlinear Control for a Voltage Source Converter

A Paper-Based Electrochemical Sensor Using Inkjet-Printed Carbon Nanotube Electrodes

Lab-on-a-Chip Systems for Aptamer-Based Biosensing