Electrohydrodynamic Direct-Writing Micro/Nanofibrous Architectures: Principle, Materials, and Biomedical Applications.

Electrohydrodynamic (EHD) direct-writing has recently gained attention as a highly promising additive manufacturing strategy for fabricating intricate micro/nanoscale architectures. This technique is particularly well-suited for mimicking the extracellular matrix (ECM) present in biological tissue, which serves a vital function in facilitating cell colonization, migration, and growth. The integration of EHD direct-writing with other techniques has been employed to enhance the biological performance of scaffolds, and significant advancements have been made in the development of tailored scaffold architectures and constituents to meet the specific requirements of various biomedical applications.

Rapid Prototyping of Thermoplastic Microfluidic 3D Cell Culture Devices by Creating Regional Hydrophilicity Discrepancy.

Microfluidic 3D cell culture devices that enable the recapitulation of key aspects of organ structures and functions in vivo represent a promising preclinical platform to improve translational success during drug discovery. Essential to these engineered devices is the spatial patterning of cells from different tissue types within a confined microenvironment. Traditional fabrication strategies lack the scalability, cost-effectiveness, and rapid prototyping capabilities required for industrial applications, especially for processes involving thermoplastic materials.

Customizable Microfluidic Origami Liver-on-a-Chip (oLOC).

The design and manufacture of an origami-based liver-on-a-chip device are presented, together with demonstrations of the chip's effectiveness at recapitulating some of the liver's key in vivo architecture, physical microenvironment, and functions. Laser-cut layers of polyimide tape are folded together with polycarbonate nanoporous membranes to create a stack of three adjacent flow chambers separated by the membranes. Endothelial cells are seeded in the upper and lower flow chambers to simulate sinusoids, and hepatocytes are seeded in the middle flow chamber.

Liver-on-a-Chip Models of Fatty Liver Disease.

As a consequence of the obesity epidemic and increasing incidence of metabolic syndrome fatty liver disease now affects a large portion of the world’s population. Left untreated, fatty liver disease can progress to more severe pathologic conditions such as cirrhosis and liver cancer. In an effort to probe the pathophysiology of fatty liver disease and its progression, research over the last decade has led to the engineering of models of the liver to aid in drug discovery and study of liver pathophysiology.

A Modular, Reconfigurable Microfabricated Assembly Platform for Microfluidic Transport and Multitype Cell Culture and Drug Testing.

Modular microfluidics offer the opportunity to combine the precise fluid control, rapid sample processing, low sample and reagent volumes, and relatively lower cost of conventional microfluidics with the flexible reconfigurability needed to accommodate the requirements of target applications such as drug toxicity studies. However, combining the capabilities of fully adaptable modular microelectromechanical systems (MEMS) assembly with the simplicity of conventional microfluidic fabrication remains a challenge. A hybrid polydimethylsiloxane (PDMS)-molding/photolithographic process is demonstrated to rapidly fabricate LEGO-like modular blocks.

Micro Motion Amplifiers for Compact Out-of-Plane Actuation.

Small-scale, out-of-plane actuators can enable tactile interfaces; however, achieving sufficient actuator force and displacement can require larger actuators. In this work, 2-mm² out-of-plane microactuators were created, and were demonstrated to output up to 6.3 µm of displacement and 16 mN of blocking force at 170 V.

Shape-Selective Assembly of Anisotropic, Deformable Microcomponents Using Bottom-Up Micromanufacturing.

A technique for shape-selective directed assembly of anisotropic, deformable, chemically-identical microcomponents onto patterned rigid templates based on shape and size differences is modeled and demonstrated. The assembly method not only controls the selective placement of the components, but also aligns the components with the assembly sites. Unlike the assembly of isotropic (spherical) microcomponents, in which only size differences can be used to discriminate among chemically-identical components to achieve selective placement, differences in both shape and size can enable selectivity in the assembly of anisotropic (non-spherical) microcomponents.

Size-selective, biocompatible, manufacturable platform for structuring deformable microsystems.

Precise, size-selective assembly and sorting are demonstrated in a low-cost system using manufacturable, replicated polymer templates to guide the assembly. Surface interactions between microscale objects and an assembly template are combined with fluid forces to drive site-selective organization of objects onto the template. Although controlling the organization of deformable objects on deformable surfaces offers a key tool for biological applications, the deformability can potentially interfere with the process that drives size selectivity.

Enhancing the tensile properties of continuous millimeter-scale carbon nanotube fibers by densification.

This work presents a study of the tensile mechanical properties of millimeter-long fibers comprising carbon nanotubes (CNTs). These CNT fibers are made of aligned, loosely packed parallel networks of CNTs that are grown in and harvested from CNT forests without drawing or spinning. Unlike typical CNT yarn, the present fibers contain a large fraction of CNTs that span the fibers' entire gauge length.

Chip-based size-selective sorting of biological cells using high frequency acoustic excitation.

This work presents the size-selective sorting of single biological cells using the assembly process known as templated assembly by selective removal (TASR). We have demonstrated experimentally, for the first time, the selective placement and sorting of single SF9 cells (clonal isolate derived from Spodoptera frugiperda (Fall Armyworm) IPLB-Sf21-AE cells) into patterned hemispherical sites on rigid assembly templates using TASR. Nearly 100% of the assembly sites on the template were filled with matching cells (with assembly density as high as 900 sites per mm(2)) within short time spans of 3 minutes.

Templated assembly by selective removal: simultaneous, selective assembly and model verification.

The use of templated assembly by selective removal to simultaneously and selectively assemble silica microspheres of two different diameters into designated sites on a surface was demonstrated. Microspheres with diameters of 636 nm and 2 µm were assembled from fluid onto templates patterned to contain holes that matched the shapes and sizes of the spherical components. The assembly experiments were carried out for a range of experimental conditions, including different fluid compositions and different intensities for the fluid excitation.

Achieving selective assembly with template topography and ultrasonically induced fluid forces.

A site-selective self-assembly technique called templated assembly by selective removal is introduced. Initial experiments demonstrated selective assembly of 1.58 mum microspheres into shape-matched holes in a lithographically defined template.