Shuxiang Cai

Abstract Cell adhesion is a basic requirement for anchorage-dependent cells to survive on the matrix. It is the first step in a series of cell activities, such as cell diffusion, migration, proliferation, and differentiation. In vivo , cells are surrounded by extracellular matrix (ECM), whose physical and biochemical properties and micromorphology may affect and regulate the function and behavior of cells, causing cell reactions. Cell adhesion is also the basis of communication between cells and the external environment and plays an important role in tissue development. Therefore, the significance of studying cell adhesion in vitro has become increasingly prominent. For instance, in the field of tissue engineering and regenerative medicine, researchers have used artificial surfaces of different materials to simulate the properties of natural ECM, aiming to regulate the behavior of cell adhesion. Understanding the factors that affect cell behavior and how to control cell behavior, including cell adhesion, orientation, migration, and differentiation on artificial surfaces, is essential for materials and life sciences, such as advanced biomedical engineering and tissue engineering. This article reviews various factors affecting cell adhesion as well as the methods and materials often used in investigating cell adhesion.

Since the late 1980s, additive manufacturing (AM), commonly known as three-dimensional (3D) printing, has been gradually popularized. However, the microstructures fabricated using 3D printing is static. To overcome this challenge, four-dimensional (4D) printing which defined as fabricating a complex spontaneous structure that changes with time respond in an intended manner to external stimuli. 4D printing originates in 3D printing, but beyond 3D printing. Although 4D printing is mainly based on 3D printing and become an branch of additive manufacturing, the fabricated objects are no longer static and can be transformed into complex structures by changing the size, shape, property and functionality under external stimuli, which makes 3D printing alive. Herein, recent major progresses in 4D printing are reviewed, including AM technologies for 4D printing, stimulation method, materials and applications. In addition, the current challenges and future prospects of 4D printing were highlighted.

Microrobots have received extensive attention in the past few decades, and the in-depth research of micro-nano processing technology and micro-nano materials has promoted the further development of microrobots. Researchers have successfully achieved the use of chemical fuels, and electric, sound, and magnetic fields to promote the movement of microrobots. Among many power sources, magnetic fields have attracted wide attention because of their advantages including remote wireless operation and harmlessness to the human body. After decades of development, magnetically driven microrobots have been extensively studied in the fields of cargo transportation, cell manipulation, toxic substance removal, and micromanipulation. This article first summarizes the driving methods of magnetically driven microrobots in recent years, then summarizes the materials for manufacturing microrobots, and summarizes the shapes of typical microrobots, including spiral, spherical, and linear structures. After that, the processing methods are sorted out, and the application of magnetic-driven microrobots in biomedicine and other fields in recent years is summarized. Finally, the development prospects of magnetic-driven microrobots are discussed.

Abstract E-jet printing is a micro- and nano-manufacturing technique that utilizes electric field-induced fluid jet printing for achieving better control and resolution than traditional jet printing processes. In addition to high printing resolution, E-jet printing has advantages in some aspects such as wide material applicability, which has been successfully applied in numerous applications that include sensors, transistors, tissue engineering scaffolds, and photonic devices. This article reviews the electrohydrodynamic jet (E-jet) printing technology, which mainly relies on the principle of electrohydrodynamic-induced fluid movement. At the same time, the process of jet formation and droplet deposition is described. The parameters, nozzle design, and ink characteristics of the jet printing process are summarized. Then, a number of concrete applications based on E-jet printing processes are described in this article. Finally, the future development of this technology has been prospected.

Three-dimensional multicellular spheroids (MCSs) have received extensive attention in the field of biomedicine due to their ability to simulate the structure and function of tissues in vivo more accurately than traditional in vitro two-dimensional models and to simulate cell-cell and cell extracellular matrix (ECM) interactions. It has become an important in vitro three-dimensional model for tumor research, high-throughput drug screening, tissue engineering, and basic biology research. In the review, we first summarize methods for MCSs generation and their respective advantages and disadvantages and highlight the advances of hydrogel and microfluidic systems in the generation of spheroids. Then, we look at the application of MCSs in cancer research and other aspects. Finally, we discuss the development direction and prospects of MCSs.