Capillary stop valve actuation by thermo-pneumatic- pressure for lab-on-chip systems
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TECHNICAL PAPER
Capillary stop valve actuation by thermo-pneumatic- pressure for labon-chip systems Ujjal Barman1,2
•
Liesbet Lagae1,2 • Benjamin Jones2
Received: 8 May 2020 / Accepted: 1 September 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A novel method is presented for triggering a robust capillary stop valve fabricated in silicon using the thermal expansion of trapped air bubble (with a footprint of just 300 lm 9 320 lm) as the actuation element. A heating element on the backside of a bubble trap chamber is utilized for thermal expansion of the air bubble. A voltage pulse of around 6 V, the capillary barrier, around 1400 Pa was easily breached. A non-dimensionalized model has been developed using equivalent circuit model to describe the complex thermal/hydraulic behavior of the system. The trapped gas bubble temperature is input as a function of time in the model. A thermal finite element-based simulation is conducted to determine the gas temperature from the experimentally measured heater temperature. The model results are validated against experiments to aid in characterizing the dynamics of the problem.
1 Introduction The relation of microvalves to a lab-on-a-chip (LOC) system is that of the heart to a circulatory system of an animal. A LOC performs its job through operations like separation, mixing, heating, biochemical reactions, etc. on biological samples using chemical reagents (Temiz et al. 2015). Microvalves can control both the quantity and timing of fluid transport within a biochip (Oh and Chong 2006). The greatest challenge, however, is the integration of these essential components into a larger microfluidic platform. Many microvalve designs have been proposed and their performance demonstrated successfully, often as standalone devices (Grover et al. 2003; Hosokawa and Maeda 2000); however, the microfluidic literature do not have many instances where these designs can be implemented or integrated to a LOC system. There are some exceptions though like the microfluidic large-scale integration (Melin and Quake 2007) where they demonstrated biological protocol automation using thousands of mechanical valves and control components using & Ujjal Barman [email protected] 1
Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200d, 3001 Heverlee, Belgium
2
Life Science Technologies Department, IMEC, Kapeldreef 75, 3001 Heverlee, Belgium
pneumatic control on a single platform constructed with multilayers of PDMS on silicon substrate. The main disadvantage of this system is the control aspect of the microvalve. For standalone platforms, any control peripherals (Shaegh et al. 2015; Pilarski et al. 2005) such as pneumatic pressure source are not desirable. Another notable work reported by Juncker et al. (2002) where pumping, valving, and synchronization of processes are performed by a capillary powered autonomous system. This system requires a large footprint of the chip to accommodate timing channels for capil
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