Microtechnology-based methods for organoid models

Innovations in biomaterials and stem cell technology have allowed for the emergence of novel three-dimensional(3D)tissue-like structures known as organoids and spheroids.As a result,compared to conventional 2D cell culture and animal models,these complex 3D structures have improved the accuracy and facilitated in vitro investigations of human diseases,human development,and personalized medical treatment.Due to the rapid progress of this field,numerous spheroid and organoid production methodologies have been published.However,many of the current spheroid and organoid production techniques are limited by complexity,throughput,and reproducibility.Microfabricated and microscale platforms(e.g.,microfluidics and microprinting)have shown promise to address some of the current limitations in both organoid and spheroid generation.Microfabricated and microfluidic devices have been shown to improve nutrient delivery and exchange and have allowed for the arrayed production of size-controlled culture areas that yield more uniform organoids and spheroids for a higher throughput at a lower cost.In this review,we discuss the most recent production methods,challenges currently faced in organoid and spheroid production,and microfabricated and microfluidic applications for improving spheroid and organoid generation.Specifically,we focus on how microfabrication methods and devices such as lithography,microcontact printing,and microfluidic delivery systems can advance organoid and spheroid applications in medicine.

Dynamic optoelectric trapping and deposition of multiwalled carbon nanotubes

In the path toward the realization of carbon nanotube(CNT)-driven electronics and sensors,the ability to precisely position CNTs at well-defined locations remains a significant roadblock.Highly complex CNT-based bottom–up structures can be synthesized if there is a method to accurately trap and place these nanotubes.In this study,we demonstrate that the rapid electrokinetic patterning(REP)technique can accomplish these tasks.By using laser-induced alternating current(AC)electrothermal flow and particle–electrode forces,REP can collect and maneuver a wide range of vertically aligned multiwalled CNTs(from a single nanotube to over 100 nanotubes)on an electrode surface.In addition,these trapped nanotubes can be electrophoretically deposited at any desired location onto the electrode surface.Apart from active control of the position of these deposited nanotubes,the number of CNTs in a REP trap can also be dynamically tuned by changing the AC frequency or by adjusting the concentration of the dispersed nanotubes.On the basis of a calculation of the stiffness of the REP trap,we found an upper limit of the manipulation speed,beyond which CNTs fall out of the REP trap.This peak manipulation speed is found to be dependent on the electrothermal flow velocity,which can be varied by changing the strength of the AC electric field.