No abstract

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

No abstract

Active pumps are often used in microfluidic devices for programmable fluid flowrate in a microchannel. Active pumps have some drawbacks due to their large size and requirement of external power. To overcome them, a new class of passive pumps based on capillary action in cellulose material, known as paper-based microfluidic pumps, has recently been explored. In this study, fluid flow in 3D paper-based pumps was investigated using flowrate measurements in microchannels. In order to develop 3D cylindrical pumps, Whatman filter paper grade 1 was shredded, mixed with water, molded and dried. The patterned serpentine channel was created using a CO2 Laser Cutting/Engraving machine. The 3D paper-based pump was integrated with microfluidic channel. The effect of paper pumps of different porosities on the fluid flowrate through a serpentine microchannel was investigated. It was found that flowrate of the fluid flowing through the channel increases with an increase in the pump’s porosity. Moreover, these pumps have the ability to transport larger volumes of liquid with improved flowrate, programmability and control, in addition to being inexpensive and simple to design and fabricate. These 3D pumps will help researchers move closer to developing an effective miniaturized diagnostic platform for point-of-care (POC) diagnostic applications.

Fabrication of conductive patterns for exible and printed electronic devices is one of the most challenging steps in the whole process. Conductive patterns in electronic devices are used as electrodes, transducers, connecting links, and sometimes, also as the active sensing elements. Since the introduction of laser induced graphene (LIG), it has been explored to print electrodes and connecting patterns for various electronic devices and systems. This work focuses on an in-house developed laser printing system and the comparison of various electrical, chemical, and morphological properties of the resulting LIG patterns using CO 2 and diode lasers. The system parameters including the laser power, relative printing speed, and the printing resolution were explored and optimized to achieve conductive patterns with varying properties suitable for different targeted applications. The fabricated patterns were characterized for their sheet resistance, surface morphology using scanning electron microscope (SEM), chemical properties using Energy Dispersive (EDS) and RAMAN spectroscopies, and physical size and resolution using optical microscopy. Continuous conductive patterns with sheet resistance in range of 11.5 Ω/□ to 43 Ω/□ were achieved using CO 2 laser with a minimum achievable pattern width of ~ 180 µm while patterns with sheet resistance in range of 19 Ω/□ to 105 Ω/□ were achieved using diode laser with a minimum pattern width of ~ 190 µm. The chemical and morphological properties of CO 2 laserbased patterns indicate the formation of 2D graphite sheets with high porosity and low O 2 concentration while the diode laser-based patterns have a lower porosity and higher percentage of O 2 indicating burning and the formation of oxides. Various applications of both types have also been discussed based on their respective properties.