Hardware
It has been already documented that bacteria culture can be grown on paper even in a
cordinated manner with the help of inkjet paper [1]. To do this, paper is completely
immersed in toluene solution of polystyrene and then completely drying for making the
hydrophobic surface [1]. Then, small patches are made by inkjet paper with toluene to
form hydrophilic patches [1]. Agar is hydrolysed by sulphuric acid for appropriate viscosity
and dispensed with inkjet printer [1]. Sodium hydroxide can be used to neutralise the agar
and sodium sulphate can be removed by electrodialysis [1]. The agar is printed on the
hydrophilic patches and can be used to grow bacteria [1]. The paper is folded in a specific
manner to be accommodated inside the device as shown in the image.
Arrangement of cultured E. coli colonies after printing on a sheet containing agar [1]
We intend to use this type of paper and fold it convoluted inside a packet of 0.2 microns filter paper thus creating a module as shown in the image.
The red section of the packet is the safe part which can be easily touched without disturbing cultures. One can hold it to pull the module outside to expose the detection part shown in yellow. If the detection shows a color change then the rest of the module can be taken out so that the co-cultured microbes can absorb the pollutants from the surrounding environment. Then the module is torn off and incinerated or disposed of as necessary.
Several of these modules are packed inside a wristband in a chain with perforated lines to tear off modules from the chain as shown in this image.
Each module is detachable and can be disposed off separately. If the pollution is more, then multiple modules can be used at once. After all the modules are consumed, the wrist band can be filled again with a new set of modules. The use of wrist band makes it user friendly and modules makes it usable multiple times.
References:
1. Srimongkon, T., Ishida, T., Igarashi, K., & Enomae, T. (2014). Development of a bacterial
culture system using a paper platform to accommodate media and an ink-jet printing to
dispense bacteria. Am. J. Biochem. Biotechnol, 10, 81-87.
