OPEN ACCESS
The number of disposable molecular diagnostics tests in the IVD market has been growing rapidly and is bound to continue to grow in the near future. The internal complexity of these rapid tests increases with the complexity of the diagnostic assay implemented by them. Some assays require precise temperature control (±1°C –5°C) for an extended time (i.e. 15–60 minutes) for the reactions involved to run properly. Microheating components in them must meet strict criteria with respect to power con- sumption, physical size and cost. The proposed finite element model is intended to provide tools for in silico validation of device designs (geometries, structural materials), as well as to help in the interpretation of heat transfer processes inside the thermal system present in a molecular diagnostics device. The proposed model was developed for and validated with polyimide etched foil heating elements actively controlled via a mini-thermostat. The thermostat was designed for battery-based operation and implemented with open-source hardware (Arduino-compatible). Plastic test structures were created that emulated disposable Lab-on-a-Chip devices with microfluidic channels to hold liquid volumes on the scale of 0.1 mL. The experimental setup was demonstrated to maintain target temperatures over at least 30 minutes with at least ±1°C around the set point operated from batteries. Physical parameters of the resistive heating element used were fed into the finite element model and simulation results compared to the performance of the aforementioned experimental setup.
computer aided design, finite element modelling, lab-on-a-chip, microfluidics, microcontrollers, resistive heating
[1] Moschou, D., Vourdas, N., Kokkoris, G., Papadakis, G., Parthenios, J., Chatzandroulis, S. & Tserepi, A., All-plastic, low-power, disposable, continuous-flow PCR chip with integrated microheaters for rapid DNA amplification. Sensors and Actuators B: Chemical, 199, pp. 470–478, 2014. http://dx.doi.org/10.1016/j.snb.2014.04.007
[2] Wang, Y., Song, H. & Pant, K., A reduced-order model for whole-chip thermal analysis of microfluidic lab-on-a-chip systems. Microfluidics and Nanofluidics, 16(1–2), pp. 369–380, 2014. http://dx.doi.org/10.1007/s10404-013-1210-0
[3] Pardy, T., Tulp, I. & Rang, T., Finite element modelling of the resistive heating of disposable molecular diagnostics devices. Computational Methods and Experimental Measurements XVII, 59, pp. 381–391, 2015. http://dx.doi.org/10.2495/cmem150341
[4] Srivastava, M., Srivastava, M.C. & Bhatnagar, S., Control Systems, Tata McGraw-Hill: New Delhi, Singapore, 2009.
[5] Meier, A.V., Electric Power Systems: A Conceptual Introduction, IEEE Press, Wiley-Interscience, Hoboken, N.J, 2006.
[6] Griffiths, D.J., Introduction to electrodynamics. Prentice Hall, 93, p. 95, 1999.
[7] Kandlikar, S.G., Garimella, S., Li, D., Colin, S. & King, M.R., Heat Transfer and Fluid Flow in Minichannels and Microchannels, Elsevier, 2006.
[8] Rood, P., A visual method of showing the high temperature coefficient of resistance of metals as compared with alloys. Journal of the Optical Society of America, 16(5), pp. 357–359, 1928. http://dx.doi.org/10.1364/JOSA.16.000357
[9] Minco Products, Inc., Flexible heaters design guide HDG01121806(A), Minco Products Inc., 2007.
[10] Craw, P. & Balachandran, W., Isothermal nucleic acid amplification technologies for point-of-care diagnostics: a critical review. Lab on a Chip, 12(14), pp. 2469–2486, 2012. http://dx.doi.org/10.1364/JOSA.16.000357
[11] Nagamine, K., Hase, T. & Notomi, T., Accelerated reaction by loop-mediated isothermal amplification using loop primers. Molecular and Cellular Probes, 16(3), pp. 223–229, 2002. http://dx.doi.org/10.1006/mcpr.2002.0415