# A Low-Cost and Portable Smart Instrumentation for Detecting Colorectal Cancer Cells
## 3 Results and Discussion
It detects the signal and transmits the measured signal to the LCD display. This microcontroller converts the analog signal generated by the photodiode using a high-precision 10-bit analog to digital converter (ADC) which is embedded inside the microcontroller. The photodiode is a semiconductor  
Figure 5: Detection of colorectal cancer cells expressing IRFP702: (**a**) colorectal cancer cells (HCT116) with IRFP702 fluorophore expression visualized under Odyssey CLx NIR scanner (LI-COR), (**b**) colorectal cancer cells (HCT116) without IRFP702 fluorophore expression visualized under Odyssey CLx NIR scanner (LI-COR), (**c**) colorectal cancer cells with IRFP702 fluorophore expression under EVOS Cell Imaging System, (**d**) excitation and emission spectra of IRFP702. This figure shows the absorption and emission spectra of the IRFP702 where the peak absorption and peak emission of the cultured sample is 673 nm and 702 nm respectively. device which converts light into current [28]. The current is produced when the photons are taken up by the photodiode. In Arduino Uno's ADC, the analog signal, which ranges from 0 to 5 V, is translated into a 10-bit code (1024 combinations) which corresponds to the analog value ranging from 0 to 1023. The Arduino Uno can read a maximum input voltage of 5 V, i.e., any voltage that is higher than 5 V will be read as 5 V regardless of their actual values. To remove this limitation, resistors of different values can be used to limit the voltage within 5 V. However, in this work, the obtained readings did not go beyond the maximum limit of the Arduino Uno as the generated fluorescence signal is not very strong. Figure 6 shows a flowchart which summarizes the working of the developed prototype. An Arduino IDE compiler is used to program the microcontroller. The code is written in C language. The device is initialized when it is first powered on. After the initial boot is successful, a sample of a control cell, which is cultured on a glass slide, is placed in the sample holder. The sample holder has a port which is designed to fit the cultured samples in it. After the sample placement is successful, the device starts reading. The microcontroller reads the data 10 times in order to reduce errors that may be caused due to manipulation, movement or placement of flashlight. The measured value is averaged, which is saved as a base value and displayed on the LCD display. This value will be used later in the calculation. It is to be noted that it is important to place the excitation source/flashlight on top of the sample, which is why a flashlight holder is used. The holder helps the user to hold the flashlight on top of the sample at the desired angle and distance away from the sample. After the reading of the control cell is completed, it is replaced with a sample of fluorescent colorectal cancer cell (HCT116 conjugated with IRFP702). As in the earlier case, the reading is performed again 10 times. This reading is averaged and compared with the previously measured value from the control cell. If the difference in voltage measurement obtained from the control cell and the fluorescent cell is greater than 700 mV, \"CancerCell Found\" is displayed. Otherwise, \"No CancerCell\" is displayed. Figure 7a,b show the control colorectal cancer cells and the IRFP702 expressing colorectal cancer cells on a glass slide respectively. Figure 7c,d show the control cells and the IRFP702 expressing colorectal cancer cells visualized with the help of a commercial system [25] respectively. From Figure 7a,b, it can be construed that it is difficult to differentiate between these cultured samples with the naked eye. However, when these same cultured colorectal cancer cells are used with our developed device, we are able to differentiate between these cells, as can be seen in Figure 7e. These readings from the samples were visualized with the help of waveform oscilloscope on a computer.