Sensors for Stretchable Electronics in Nanotechnology

Kaushik Pal, Kaushik Pal

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000431674
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

Sensors for Stretchable Electronics in Nanotechnology discusses the fabrication of semiconducting materials, simple and cost-effective synthesis, and unique mechanisms that enable the fabrication of fully elastic electronic devices that can tolerate high strain. It reviews specific applications that directly benefit from highly compliant electronics, including transistors, photonic devices, and sensors.

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• Discusses ultra-flexible electronics, highlighting its upcoming significance for the industrial-scale production of electronic goods

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• Outlines the role of nanomaterials in fabricating flexible and multifunctional sensors and their applications in sensor technologies

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• Covers graphene-based flexible and stretchable strain sensors

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• Details various applications including wearable electronics, chemical sensors for detecting humidity, environmental hazards, pathogens, and biological warfare agents, and biosensors for detecting vital signals

This book is a valuable resource for students, scientists, and professionals working in the research areas of sensor technologies, nanotechnology, materials science, chemistry, physics, biological and medical sciences, the healthcare industry, environmental science, and technology.

1 Introduction to Sensor Nanotechnology and Flexible Electronics

Alaa A. A. Aljabali,Kamal Dua,Kaushik Pal, and Murtaza M. Tambuwala

CONTENTS

1.1Introduction

1.2Wearable Electronics

1.3Wearable Actuators

1.4Wearable Sensors

1.5Electrical Sensing

1.6Optical Sensing

1.1 Introduction

Current advances in low-power electronic smartphone and wearable devices, modern data acquisition methods, and the ICT environment have opened up prospects for a fresh approach in health and medicine. Health services are continually moving towards a preventive, patient-centered approach, replacing the old hospital-based model. In the early 2000s, developments in intelligent clothing were regarded as vital, leading to the production of fabrics with embedded sensors that connect to portable personal digital assistance systems, which minimized both morbidity and medical costs associated with the vascular system [1, 2]. Flexible electronics research has evolved dramatically over the past decade. A vast number of versatile systems like displays and sensors have been developed by researchers from around the world. Material advances have been crucial to scientific progress in this area in recent years [3]. Transistors, connectors, memory cells, passive components, and other products make it difficult to make portable electronics a reality. Nanostructures of different forms have provided a suitable medium for designing highly efficient semiconductors, dielectric materials, and conductors with nanoparticles (NPs), nanotubes, nanowires, and organic matter for various electronic medical applications [4, 5].

More recently, portable clothing devices have been considered for preventing and enhancing well-being and active aging, for successful reduction of physical age and behavioral decline, and for sustainable medical infrastructure. These objectives can be achieved through mobile and customized wellness initiatives, which pose many obstacles, such as portable electronics energy autonomy [6].

Flexible sensors can be considered as superior materials for smart sensing systems such as electronic products, prosthetics, robotics, medical treatments, protective equipment, pollution monitoring, environmental monitoring, domestic travel, and protective space travel [7]. There is an emerging trend towards producing reliable real-world flexible sensors that rely on NPs between 10 nm and 100 nm in diameter.

There are several other reasons why the use of NPs for flexible sensors (including in materials) is exciting. The first concerns the assumed capacity to synthesize almost any form of NP, if not at will then with considerable power. Several research experiments have shown that NPs are controllable, with cores made of pure metal (e.g. Au, Ag, Co, Pt, Pd, Cu, Al) or metallic composites (e.g. Pd, Pt, NiFe/Pt, Au/Ag/Cu, Au/Ag/Cu/Pd, Au/Ag, Au) [8–10]. The second reason is that NPs can be sustained with a wide range of chemical ligands: alkyl thiols and alkanaethiolates, arenethiolates, alkyl-trimethyloxysilans, xanthates, oligonucleotides, dialkyl disulfides, proteins, sugars, phospholipids, and enzymes. This suggests that NPs with a combination of chemical and physical functions can be obtained for sensing applications and can significantly impact the sensitivity and selectiveness of sensors, as shown in Figure 1.1 [11–13].

Figure 1.1Schematic illustration of flexible nanoelectronics used as biosensors to monitor health and well-being.

The third reason is the potential to vary the scale and form of NPs and thus the ratio between surface and volume (in spheres, rectangles, hexagons, cubes, triangles, and star-and-branch-like outlines). These features would allow for control over the surface properties of materials and the resulting ‘quality,’ with physicochemical characteristics like strain, temperature, plasmon resonance, and much more [14, 15].

Smartphones represent a relatively new and quickly produced commercial electronics platform that has allowed more comfortable and faster communication between people. Intensive development is now being carried out in portable electronics that can offer a much more convenient electronic interface than smartphones [16]. Importantly, many foldable electronics products/prototypes have already been introduced and can also be categorized as wearable electronics [17, 18]. The mechanical flexibility of electronics offers an opportunity to operate on a substratum with no specified shape, and therefore mechanical versatility enables the safe movement of electronics on a wide range of object surfaces, including bodies. Thus, it is anticipated that flexible/extensible electronics can have a variety of uses. The applications provide biomedical electronics and electronics for tracking social media and the Internet and external climate monitoring systems [19–21].

Nanomaterials have superior stability in integrating versatile electronics and are suitable for diverse applications in a wide variety of surface environments. This chapter briefly presents the essential properties of nanomaterials and summarizes the advances in applying those properties in different types of instruments, such as electrical and optical devices [22].

The production of compact and stretchable electrodes is one of the most critical aspects in manufacturing flexible electronics. Different standard electrodes, including those made of gold, copper, aluminum, and indium tin oxide, have been used as conventional conductive materials because of their excellent electrical conductivity. However, because of their fragility, these are difficult to use in flexible electronics. Numerous modern materials are, therefore, being produced for use in flexible electronics. Among these new materials are 1D nanomaterials, which are currently being researched for their use as versatile conducting compounds.

A 1D nanostructure typically has metal nanostructures, metal nanomaterials, and carbon nanomaterials (CNTs). The advantages of high conductivity and excellent mechanical deformations result in structural characteristics with a high aspect ratio [23]. The 1D design provides a straight route for the transport of loads and reduces grain borders or defects. In the event of deformations, cracks are preferentially produced mostly on grain borders or other defects. Since such cracks result in a drastic rise in resistance as charging transport is removed, as much stretchability as possible is needed to avoid cracks [24]; for example, 1D nanomaterials with an area ratio above 100 nm in diameter that reflect silver nanowires (AgNWs) and iD materials with a diameter less than 100 nm that reflect cotton nanowires (CuNWs).

In addition, they have a sheet resistance smaller than 20 Ω per sq⁻¹ and propagation of 85% or higher in the AgNWs’ permeating networks. A large number of studies have also been done on flexible transparent electrode products to replace conventional porous TiO. The interactions between the nanowires have a significant advers...