involves both two-dimensional (2D) or three-dimensional (3D) flow-systems.
Various techniques are used for making 3D systems like sticking various patterned
layers together or folding a single patterned layer. 3D devices are getting popular as
they have increased functionality without increasing the size of device [29].
2.2 Recent Studies Based on Paper Based Microfluidic
Sensors
The common detection techniques used by the paper based microfluidic devices are
namely colorimetric, luminescence, electrochemical, and photoelectrochemical
detection [21]. For on-site analysis, it is important that the detection method used is
portable and user friendly. Khanna et al. [30] reported the estimation of Bisphenol-A
concentration in ethanol. They used nanostructured manganese dioxide as a receptor.
Meelapsom et al. [31] developed a microfluidic Paper-based Analytical Device by
using alkyl ketene dimer-inkjet printing. They used unmodified silver nanoparticles
which disintegrated on exposure to mercury (II). Several options are available for
onsite analysis like use of smartphones [32–34], portable scanners [35] or purpose
built-in detector [36, 37]. Recently, smartphones have gained attention from
researchers as they are more advantageous than use of a simple camera. While using
smartphones applications can be developed for internal monitoring as done by
Sicard et al. [33], which helps easy collection, storage and real time sharing of data.
Care must be taken for uniform light exposure when the cameras of mobile phones
are used. Ortiz-Gomez et al. [32] kept phone with flash off condition in a box having
LED to control light exposure. Smartphones can be used both with [38] or without
flash [33] with the use of forming a control zone when taking the picture. Santhiago
et al. [34] demonstrated the use of mobile phone for detection with incorporation of a
Quick Response (QR) code reader which reads the information from the microfluidic
device.
2.3 Future Trends and Recommendations
Paper based microfluidic devices are developed to be portable, but a few have been
used for the field tests. Wax printing/paper cutting is the commonly used fabrication
methods used for the development of paper based microfluidic devices. Fabrication
methods selected should be simple and low cost and must be suitable for scaling up
of devices. It has been reported that smart phones and tablets with dedicated
applications are fit for image capture, real time processing, storing and sharing of
data. Use of such tools helps to make the device user friendly and portable.
Smartphones connected to the microfluidic devices are also beneficial to areas
Emerging Techniques and Materials for Water Pollutants Detection
281
Various techniques are used for making 3D systems like sticking various patterned
layers together or folding a single patterned layer. 3D devices are getting popular as
they have increased functionality without increasing the size of device [29].
2.2 Recent Studies Based on Paper Based Microfluidic
Sensors
The common detection techniques used by the paper based microfluidic devices are
namely colorimetric, luminescence, electrochemical, and photoelectrochemical
detection [21]. For on-site analysis, it is important that the detection method used is
portable and user friendly. Khanna et al. [30] reported the estimation of Bisphenol-A
concentration in ethanol. They used nanostructured manganese dioxide as a receptor.
Meelapsom et al. [31] developed a microfluidic Paper-based Analytical Device by
using alkyl ketene dimer-inkjet printing. They used unmodified silver nanoparticles
which disintegrated on exposure to mercury (II). Several options are available for
onsite analysis like use of smartphones [32–34], portable scanners [35] or purpose
built-in detector [36, 37]. Recently, smartphones have gained attention from
researchers as they are more advantageous than use of a simple camera. While using
smartphones applications can be developed for internal monitoring as done by
Sicard et al. [33], which helps easy collection, storage and real time sharing of data.
Care must be taken for uniform light exposure when the cameras of mobile phones
are used. Ortiz-Gomez et al. [32] kept phone with flash off condition in a box having
LED to control light exposure. Smartphones can be used both with [38] or without
flash [33] with the use of forming a control zone when taking the picture. Santhiago
et al. [34] demonstrated the use of mobile phone for detection with incorporation of a
Quick Response (QR) code reader which reads the information from the microfluidic
device.
2.3 Future Trends and Recommendations
Paper based microfluidic devices are developed to be portable, but a few have been
used for the field tests. Wax printing/paper cutting is the commonly used fabrication
methods used for the development of paper based microfluidic devices. Fabrication
methods selected should be simple and low cost and must be suitable for scaling up
of devices. It has been reported that smart phones and tablets with dedicated
applications are fit for image capture, real time processing, storing and sharing of
data. Use of such tools helps to make the device user friendly and portable.
Smartphones connected to the microfluidic devices are also beneficial to areas
Emerging Techniques and Materials for Water Pollutants Detection
281