Using polymers for the fabrication of microfluidic systems is an area of research under investigation owing to its utilities in both medical and engineering applications.
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Microfluidics is the study of the behavior, precision command and control of liquids geometrically limited to a tiny scale, where surface forces outweigh volumetric forces. With this technique, one may perform scientific analysis on a small number of samples, making it highly economical.
Importance of Sensors in Microfluidics
Microfluidic techniques have been increasingly employed in various applications. To measure the flow rate of liquids of such small samples, very accurate sensors are required, referred to as ‘microfluidic sensors’.
Generally, a precision syringe pump and Coriolis mass flowmeter are used for this purpose. One problem with these sensors is that they occupy a lot of space, are expensive and are complex to operate.
To miniaturize microfluidic sensors, scientists have proposed an alternative; Micro-Electro-Mechanical-System (MEMS) based sensors. They are desirable because of their lower cost, high precision and portability.
MEMS can be classified into two types; thermal or non-thermal. The heat exchange intensity is used by thermal flow sensors to calculate flow velocity. This approach ensures excellent measurement sensitivity and accuracy, as well as low output signal drift.
Other non-thermal flow sensors exist, such as flowrate detection, based on differences throughout the conductance of microwave resonator and a digitized volume dispensing system that detects droplet production frequency electrically. The former type is still more commercially available owing to its high measuring precision.
This type of sensor has also piqued attention as a helpful device for performing activities such as groupings, interactions, and detecting diverse materials and particles, thanks to employing a minimal quantity of samples.
DNA testing, drug delivery, as well as other rapid testing services for diseases such as SARS-CoV-2, herpes, HIV, and Hepatitis A, B and C have all made use of this technology.
Background Theory
The microchannel – hydraulic channels with a diameter less than one mm inside a flowmeter – walls are stressed in both tangent & normal directions by a fluid. Changes in velocity pressure (normal stress) and (shear stress) within the microchannel cause this stress.
The tension produced by the fluid is tangent to the wall in a horizontal cantilever. At the same time, the stress is increased to the face of the wall at an angle in a curved cantilever, causing the cantilever to move along the flow direction and bend.
The Problem at Hand
Numerous commercially available conventional flowmeters cannot measure extremely low flow, which is necessary where the sample is scarce in volume. In such cases, increasing measurement accuracy is crucial. Otherwise, alternative methods to measuring flow in a microchannel should be explored.
A Novel Approach to the Problem
Mohammadamini et al (2022) conducted research to measure the liquid flow rate in a microchannel using a newly formed suspended polymeric microfluidic device. As per the results, the greater the surface perpendicular to the flow, the more fluid can enter the cantilever, forcing it to bend more. The constructed polymeric suspended flowmeter detected flow rate in the range of 100 μl/min to1000 μl/min and had a sensitivity less than 0.130 μm/(μl/min).
Results also indicated that a curved cantilever construction is preferable to a flat one for precise measurement. Hence, a cantilever geometry is superior to a straight flowmeter.
Albeit a small niche in the subject, the study had been an attempt to develop an appropriate microfluidic flowmeter. Because of its basic construction comprising of only two thin sheets of polymers as well as the carbon dioxide laser engraving technology required for its creation, the suggested flowmeter had a reasonable price and a straightforward manufacturing procedure.
Other benefits include good sensitivity and predictable cantilever bending based on varied fluid flows. In terms of precision and reproducibility, the findings were satisfactory, with an error rate of less than 2 %.
What to Expect in the Future?
The team’s investigation builds on previously recognized fundamentals of microtechnology and attempts to find an improved flowmeter sensor for measuring low-volumes accurately.
The high-scale production of such technology is not entirely economical, and thus, for commercialization aspects, a more appropriate detecting technology, such as a capacitive or resistance approach, should be used.
Future advancements in setups for downsizing composition preparation employing microfluidic chips may enable on-demand manufacture of nanomedicine products in the clinical context, allowing for efficient manufacturing and administration of customizable medication formulations based on patient data.
It is also expected to play an important part in pharmaceutical technologies and future medical applications, including drug production and administration, as well as intelligence analysis.
Flowmeter Calibration: Understanding How Best to Proceed
References and Further Reading
Mohammadamini, F., Rahbar Shahrouzi, J., & Samadi, M. (2022). A suspended polymeric microfluidic sensor for liquid flow rate measurement in microchannels. Scientific Reports, 12. Available at: https://doi.org/10.1038/s41598-022-06656-z
Bohr, A., Colombo, S., & Jensen, H. (2019). Future of microfluidics in research and in the market. Microfluidics for Pharmaceutical Applications. Available at: https://doi.org/10.1016/B978-0-12-812659-2.00016-8
Ejeian, F., Azadi, S., Razmjou, A., Orooji, Y., Kottapalli, A., Warkiani, M. E., & Asadnia, M. (2019). Design and applications of MEMS flow sensors: A review. Sensors and Actuators A: Physical, 295. Available at: https://doi.org/10.1016/j.sna.2019.06.020
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