Integrated Microfluidic Membrane Transistor Utilizing Chemical Information for On-Chip Flow Control

Abstract

Microfluidics is a great enabling technology for biology, biotechnology, chemistry and general life sciences. Despite many promising predictions of its progress, microfluidics has not reached its full potential yet. To unleash this potential, we propose the use of intrinsically active hydrogels, which work as sensors and actuators at the same time, in microfluidic channel networks. These materials transfer a chemical input signal such as a substance concentration into a mechanical output. This way chemical information is processed and analyzed on the spot without the need for an external control unit. Inspired by the development electronics, our approach focuses on the development of single transistor-like components, which have the potential to be used in an integrated circuit technology. Here, we present membrane isolated chemical volume phase transition transistor (MIS-CVPT). The device is characterized in terms of the flow rate from source to drain, depending on the chemical concentration in the control channel, the source-drain pressure drop and the operating temperature.

High Integration of Microfluidic Circuits Based on Hydrogel Valves for MEMS Control

“…Depending on the concentration the hydrogel changes its size and therefore the fluidic resistance of the valve. In this way the CVPT acts like a chemofluidic transistor which was published by Frank et al…”

“…Valves are essential in channel‐based microfluidics. Valves are used for active manipulation/control of small fluid flow inside channel networks, to form separated compartments for (bio‐)chemical reactions and cultivation studies in parallel or high‐throughput.…”

“…Using stimuli‐sensitive hydrogels like poly‐ N ‐isopropylacrylamide (PNIPAAm) as active material for microfluidic valves is a common technique . Hydrogel‐based valves can be controlled by an electric or magnetic field glucose or ethanol concentrations, temperature, light, and the pH value . However, present technologies for hydrogel‐based valves lack in a method or concept, which allows the fabrication and control of microfluidic systems with tens to hundreds of valves.…”

“…The batch fabrication method allowed the realization of a large‐scale integrated tactile micro‐electro‐mechanical‐systems (MEMS) display with more than 4.300 hydrogel actuator pixels . Nevertheless, the only reported hydrogel‐based mLSI labs on a chip, the chemofluidic ICs described in previous publication are primarily fabricated by manual pick‐and‐place of the gel structures inside the channel structures. The unsolved problem is the implementation of the operating point defined by design of the components like valves, chemofluidic switches, and transistors.…”

Unsteadily manipulating internal flow barriers

“…This may help address broader goals of flow control such as ensuring robust flow properties (Brunton & Noack 2015;Kucala & Biringen 2014;Fish & Lauder 2006;Karnik et al 2007;Sattarzadeh & Fransson 2016;Tounsi et al 2016;Boujo et al 2015) or enhancing or suppressing mixing (Ho & Tai 1998;Park et al 2014;Cheikh & Lakkis 2016). The methods described in this paper are therefore from a different angle than more established flow control methods such as velocity modification based on flow sensing (Beebe et al 2000;Frank et al 2016;Jadhav et al 2015;Tounsi et al 2016), stabilising unstable or chaotic trajectories (Ott et al 1990;Boccaletti et al 2000;Pyragas 1992;Tamaseviciute et al 2013), controlling autonomous vehicles by sampling fluid velocities (Heckman et al 2015;Michini et al 2014;Mallory et al 2013;Senatore & Ross 2008), designing optimal geometries for microfluidic devices (Jeong et al 2016;Ionov et al 2006;Balasuriya 2015), determining control velocities for energy/enstropyconstrained mixing (Lin et al 2011;Hassanzadeh et al 2014;Cortelezzi et al 2008;Mathew et al 2007;Balasuriya & Finn 2012), and many others (Kim & Bewley 2007). Knowing the Eulerian velocities which engender a particular unsteady flow barrier can be used as a condition to build various control strategies: determining the optimal global Eulerian velocity to control flow barriers, finding a control forcing that must be applied, determining where to place flow actuators and when to invoke them, etc.…”