Nanotechnology for Microfluidics

Xingyu Jiang, Chunli Bai, Minghua Liu

• Publisher: Wiley-VCH
• Year: 2019
• Print ISBN: 9783527345335
• eBook ISBN: 9783527818358
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Analytic Chemistry
• Index: Technology & Engineering

The book focuses on microfluidics with applications in nanotechnology. The first part summarizes the recent advances and achievements in the field of microfluidic technology, with emphasize on the the influence of nanotechnology. The second part introduces various applications of microfluidics in nanotechnology, such as drug delivery, tissue engineering and biomedical diagnosis.

1
Micro/Nanostructured Materials from Droplet Microfluidics

Xin Zhao¹, Jieshou Li¹, and Yuanjin Zhao^1,2

¹Medical School of Nanjing University, Research Institute of General Surgery, Jinling Hospital, No. 305, East Zhongshan Road, Xuanwu District, Nanjing, 210002, P. R. China

²Southeast University, State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, No. 2, Sipailou, Xuanwu District, Nanjing, 210096, P. R. China

1.1 Introduction

Since the emergence of microfluidics at the beginning of 1980s, microfluidic technologies have been extensively applied in the fabrication of materials with specific physicochemical features and versatile applications [1–3]. This relatively new field is the synergy of science and technology of systems with integrated channels on the microscale dimensions, through which small quantities of fluids (usually 10⁻⁹ to 10⁻¹⁸ l) can flow in designed configurations and are precisely controlled and manipulated [4–6]. In the field of microfluidics, as fluid dimensions shrink to the microscale level, their specific surface area increases, thus showing behaviors divergent from those of macroscopic fluids, which can be characterized by three major phenomena: highly efficient mass–heat transfer, relative dominance of viscous force over inertial force, and significant surface effects [7,8]. In addition, the high integration of microfluidic channels facilitates the coexistence and diverse interactions of multiple fluid phases and paves the way for miniaturized systematic control over individual fluids and fluid interfaces [9,10]. These features offer obvious advantages over bulk synthesis, most notably in their ability to ensure monodispersity and control the structure of final products [11–13]. Therefore, microfluidics has promoted the development of multidisciplinary research in physical, chemical, biological, medical, and engineering fields.

Droplet microfluidics is an important subcategory of the microfluidic technologies, which generates and manipulates discrete droplets through immiscible multiphase flows inside the microchannels [14–16]. In the past two decades, fostered by great progress in both theoretical and technical aspects, droplet microfluidics has fulfilled original expectations and become a significant approach to generate materials for a broad range of applications [17–19]. The basic principles and microfluidic devices for droplet generation are shown in Figure 1.1, including a T‐junction chip (Figure 1.1a), a flow‐focusing chip (Figure 1.1b), and a coaxial structured chip (Figure 1.1c) [20]. In the T‐junction chip, the dispersed phase flows from a vertical channel to a horizontal channel filled with the continuous phase. Under the combined action of both shear force and extrusion pressure from the continuous phase, monodispersed droplets are generated. In the flow‐focusing chip, the dispersed phase flows from the middle channel and undergoes extrusion force of the continuous phase from all directions. The dispersed phase experiences stretching and breakage, leading to droplet formation. In the coaxial structured chip, the dispersed phase channel is embedded in the continuous phase channel, and the dispersed phase flows parallel to the continuous phase toward the same direction. Also, the dispersed phase is broken into droplets. In microfluidic systems, droplet generation is influenced by microchannel construction, viscosity and flow velocity of each phase, and interfacial tension between adjacent flows. Therefore, the dimensions and production rates of droplets can be regulated by adjusting the above parameters. In addition, through a flexible design of microchannels, double or even multiple emulsions could be generated in a controlled manner (Figure 1.1d,e) [21,22]. These microfluidic droplets have diverse morphologies and components and can serve as excellent templates to synthesize materials with specific structures and functions.

With the development of microfabrication technology, considerable research has been made to synthesize microstructured materials (MMs)/nanostructured materials (NMs) because the microscopic architectures give additional properties to the materials [23–26]. Conventional bulk methods usually adopt a certain physical or chemical procedure (e.g. mechanical stirring) [27,28]. These methods usually generate materials with a monotonous morphology, and the dispersity of products and synthetic processes are difficult to control [29,30]. In particular, for fabrication of composite materials, such as “intelligent materials” or “core–shell materials,” the conventional approaches are insufficient to meet the requirements. MMs/NMs synthesized from droplet microfluidics possess narrow size distribution, flexible structures, and desired properties [31–33]. Compared to conventional methods, the advantages of microfluidic synthesis lie in the following aspects [20,34–36]. The material size, structure, and composition are easily controlled, resulting in superior properties and functions. The addition of reagents is very simple, which is beneficial for the manipulation of multistep and multireagent synthesis. Through scale integration of microfluidic systems and equipment automation, the complex reaction process can be largely simplified. Because majority of materials used to make microfluidic chip are facilitated to be observed, real‐time monitoring of the reaction process could be realized, which helps to clarify the synthesis mechanism. Therefore, the application of droplet microfluidics to design and prepare MMs/NMs has become a hot topic recently and will bring about infinite possibilities for the future development of materials science.

In this chapter, we summarize the classical and recent achievements in the MMs/NMs engineered from droplet microfluidics and their various applications. We first provide an overview of MMs fabricated by droplet microfluidics, including the droplet formation mechanism and various microchips used to generate different droplets, the methods to prepare MMs templated from these droplets, and the unique and complex structures enabled by microfluidic techniques. We then present basic synthesis methods for inorganic and organic NMs through droplet microfluidics, and the heterogeneous and multifunctional nanostructures from microfluidic platforms are also introduced. Following these two sections, much emphasis will be laid on the applications of the generated MMs/NMs, including drug delivery, cell encapsulation, TE, and analytical applications. Finally, we will discuss the current status and existing challenges and provide opinions on the directions of future development of droplet microfluidics in the synthesis of advanced MMs/NMs.

Figure 1.1 (a–c) The principles and chip designs with different flow regimes for droplet generation, including T‐junction (a), flow‐focusin...

Table of contents

• Cover
• Table of Contents
• Preface
• 1 Micro/Nanostructured Materials from Droplet Microfluidics
• 2 Digital Microfluidics for Bioanalysis
• 3 Nanotechnology and Microfluidics for Biosensing and Biophysical Property Assessment: Implications for Next‐Generation in Vitro Diagnostics
• 4 Microfluidic Tools for the Synthesis of Bespoke Quantum Dots
• 5 Microfluidics for Immuno‐oncology
• 6 Paper and Paper Hybrid Microfluidic Devices for Point‐of‐care Detection of Infectious Diseases
• 7 Biological Diagnosis Based on Microfluidics and Nanotechnology
• 8 Recent Developments in Microfluidic‐Based Point‐of‐care Testing (POCT) Diagnoses
• 9 Microfluidics in Microbiome and Cancer Research
• 10 Microfluidic Synthesis of Functional Nanoparticles
• 11 Design Considerations for Muscle‐Actuated Biohybrid Devices
• 12 Micro‐ and Nanoscale Biointerrogation and Modulation of Neural Tissue – From Fundamental to Clinical and Military Applications
• Index
• End User License Agreement