Nanofibrillated cellulose paper (nanopaper) has gained
growing
interest as one promising substrate material for paper-based microfluidics,
thanks to its ultrasmooth surface, high optical transparency, uniform
nanofiber matrix with nanoscale porosity, and tunable chemical properties.
Recently, research on nanopaper-based microfluidics has quickly advanced;
however, the current technique of patterning microchannels on nanopaper
(i.e., 3D printing, spray coating, or manual cutting and sticking),
that is fundamental for application development, still has some limitations,
such as ease-of-contamination, and more importantly, only enabling
millimeter-scale channels. This paper reports a facile process that
leverages the simple operations of microembossing with the convenient
plastic micro-molds, for the first time, patterning nanopaper microchannels
downing to 200 μm, which is 4 times better than the existing
methods and is time-saving (<45 mins). We also optimized the patterning
parameters and provided one quick look-up table as the guideline for
application developments. As proof-of-concept, we first demonstrated
two fundamental microfluidic devices on nanopaper, the laminar-mixer
and droplet generator, and two functional nanopaper-based analytical
devices (NanoPADs) for glucose and Rhodamine B (RhB) sensing based
on optical colorimetry and surface-enhanced Raman spectroscopy, respectively.
The two NanoPADs showed outstanding performance with low limits of
detection (2 mM for glucose and 19fM for RhB), which are 1.25×
and 500× fold improvement compared to the previously reported
values. This can be attributed to our newly developed highly accurate
microchannel patterning process that enables high integration and
fine-tunability of the NanoPADs along with the superior optical properties
of nanopaper.
Caenorhabditis elegans
(
C. elegans
) has been a popular model organism for several decades since its first discovery of the huge research potential for modeling human diseases and genetics. Sorting is an important means of providing stage- or age-synchronized worm populations for many worm-based bioassays. However, conventional manual techniques for
C. elegans
sorting are tedious and inefficient, and commercial complex object parametric analyzer and sorter is too expensive and bulky for most laboratories. Recently, the development of lab-on-a-chip (microfluidics) technology has greatly facilitated
C. elegans
studies where large numbers of synchronized worm populations are required and advances of new designs, mechanisms, and automation algorithms. Most previous reviews have focused on the development of microfluidic devices but lacked the summaries and discussion of the biological research demands of
C. elegans
, and are hard to read for worm researchers. We aim to comprehensively review the up-to-date microfluidic-assisted
C. elegans
sorting developments from several angles to suit different background researchers, i.e., biologists and engineers. First, we highlighted the microfluidic
C. elegans
sorting devices' advantages and limitations compared to the conventional commercialized worm sorting tools. Second, to benefit the engineers, we reviewed the current devices from the perspectives of active or passive sorting, sorting strategies, target populations, and sorting criteria. Third, to benefit the biologists, we reviewed the contributions of sorting to biological research. We expect, by providing this comprehensive review, that each researcher from this multidisciplinary community can effectively find the needed information and, in turn, facilitate future research.
The development of multifunctional nanomaterials has received growing research interest, thanks to its ability to combine multiple properties for severing highly demanding purposes. In this work, holmium oxide nanoparticles are synthesized and characterized by various tools including XRD, XPS, and TEM. These nanoparticles are found to emit near-infrared fluorescence (800–1100 nm) under a 785 nm excitation source. Imaging of the animal tissues was demonstrated, and the maximum imaging depth was found to be 2.2 cm. The synthesized nanoparticles also show the capability of facilitating dye (fluorescein sodium salt and rhodamine 6G) degradation under white light irradiation. The synthesized holmium oxide nanoparticles are envisioned to be useful for near-infrared tissue imaging and dye-degradation.
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