Ultra-Low-Cost Integrated Silicon-based Transducer for On-Site, Genetic Detection of Pathogens

Estefania Nunez-Bajo; Michael Kasimatis; Yasin Cotur; Tarek Asfour; Alex Collins; Ugur Tanriverdi; Max Grell; Matti Kaisti; Guglielmo Senesi; Karen Stevenson; Firat Guder

Although we expected formation of Schottky barriers and non-linear electrical characteristics across the Au-Si interface, the I-V measurements ( Figure 3C ) demonstrated that the junction exhibits relatively ohmic behavior with a linear I-V relationship (R 2 =0.9996) between -5V and +5V. The Si substrate plus the Au contacts can, therefore, be modeled as a simple variable resistor, the magnitude of which changes with temperature. We have designed a custom electrical circuit ( Figure 3D ) and MATLAB-based graphical user interface ( Figure S4 ) to control the temperature of the TriSilix chip at a precise setpoint through software control. The circuit ( Figure 3D ) implements a voltage controlled constant current source which can be adjusted digitally using a low-cost microcontroller (Arduino Due). This circuit can also measure the voltage drop across the TriSilix chip; when a constant current is applied, the resistance (hence the temperature) of the TriSilix thermistor can be calculated using the voltage reading, and Ohm's law. Using the MATLAB program and the custom electrical circuit board, we were able to run a temperature program ( Figure 3E ) and maintain the TriSilix chip at a given temperature setpoint over time. This is crucial for both cyclic and isothermal NA amplification reactions.