Highlights  Cell spheroids are spherical aggregates best mimicking the tissue microenvironment.  Spheroid culture better recapitulates the in-vivo condition in microfluidic chips.  Microfluidics provides rapid spheroid formation with size uniformity and control.  These chips contain microwells, microstructures, droplet generators, etc.  To fabricate such chips, some design considerations must be taken into account.

Lab-on-a-chip technology is an emerging field evolving from the recent advances of micro- and nanotechnologies. The technology allows the integration of various components into a single microdevice. Microfluidics, the science and engineering of fluid flow in microscale, is the enabling underlying concept for lab-on-a-chip technology. The present paper reviews the design, fabrication and characterization of drug delivery systems based on this amazing technology. The systems are categorized and discussed according to the scales at which the drug is administered. Starting with the fundamentals on scaling laws of mass transfer and basic fabrication techniques, the paper reviews and discusses drug delivery devices for cellular, tissue and organism levels. At the cellular level, a concentration gradient generator integrated with a cell culture platform is the main drug delivery scheme of interest. At the tissue level, the synthesis of smart particles as drug carriers using lab-on-a-chip technology is the main focus of recent developments. At the organism level, microneedles and implantable devices with fluid-handling components are the main drug delivery systems. For drug delivery to a small organism that can fit into a microchip, devices similar to those of cellular level can be used.

The interdisciplinary research field of microfluidics has the potential to revolutionize current technologies that require the handling of a small amount of fluid, a fast response, low costs and automation. Microfluidic platforms that handle small amounts of liquid have been categorised as continuous-flow microfluidics and digital microfluidics. The first part of this paper discusses the recent advances of the two main and opposing applications of liquid handling in continuous-flow microfluidics: mixing and separation. Mixing and separation are essential steps in most lab-on-a-chip platforms, as sample preparation and detection are required for a variety of biological and chemical assays. The second part discusses the various digital microfluidic strategies, based on droplets and liquid marbles, for the manipulation of discrete microdroplets. More advanced digital microfluidic devices combining electrowetting with other techniques are also introduced. The applications of the emerging field of liquid-marble-based digital microfluidics are also highlighted. Finally, future perspectives on microfluidic liquid handling are discussed.

In this review, we have summarised the synthesis and classification of common nanozymes and their applications in electrochemical biosensor development.

The fields of assisted reproductive technology (ART) and in vitro fertilization (IVF) have progressed rapidly, yet still need further improvements. Microfluidic technology can incorporate various ART procedures such as embryo/gamete (sperm/oocyte) analysis, sorting, manipulation, culture, and monitoring. The introduction of paper‐based and droplet‐based microfluidics further improves the commercialization potential of this technology. The progress in 3D printing technology allows for the integration of microfluidics with tissue engineering that may revolutionize current practices in biology and medicine. This review categorizes ART methods according to continuous‐flow microfluidics, paper‐based microfluidics, droplet‐based microfluidics, and organ‐on‐a‐chip. The advances are summarized and potential opportunities in infertility diagnosis, sperm selection, sperm guidance, oocyte selection, insemination, embryo culture, embryo monitoring, and cryopreservation are identified. While some advances of continuous‐flow microfluidics for ART have already been reviewed, other microfluidic techniques are still in their early stages. It is envisioned that advances in droplet‐based microfluidics, especially digital microfluidics, will allow for more progress in human IVF, particularly single embryo transfer. Droplet‐based microfluidics may also lead to fully integrated and high‐throughput platforms for animal IVF. Recent advances in organ‐on‐a‐chip including ovary/uterus/oviduct‐on‐chip platforms hold promise for the integration of the whole human reproductive system‐on‐a‐chip for clinical applications.