Devices

Devices

chaired by Joost Lötters & David Fernandez Rivas

Abstracts

Standardized Parallelization of Microfluidic Devices Containing Hundreds of Microvalves, Anke Vollertsen (BIOS)

Standardized, high-throughput microfluidic devices are necessary to translate discoveries made in academia to applications in an industrial setting. Here we present a modular platform which can parallelize microfluidic large-scale integration (mLSI) chips. The platform consists of two parts: a fluidic circuit board (FCB) and three microfluidic building blocks (MFBBs). An integrated valve set forms a chip 'select' function in the FCB, allowing any or all of the MFBBs to be enabled or disabled. We characterized the valves' closing behavior at different pumping and gating pressures. Each MFBB is a mLSI chip which contains over 750 microvalves with which 64 microchambers can be independently addressed. As a result, a total of 192 chambers can be filled and purged with spatial and temporal independence. Furthermore, the dimensions of both the MFBB and the platform are standardized in accordance with the ISO Workshop Agreement 23:2016 standards. This standardized, modular approach facilitates further scalability, ultimately bringing the experimental setting in academia one step closer to an industrial setting.

Micromachined electrodes for electrolyzers, Peter van der Linde (MCS)

The demand for hydrogen gas increases with the diminishing gas and oil reserves. Simultaneously, CO2 emission levels need to be reduced to counter climate change. Hydrogen is an energy carrier that could partially replace the use of fossil fuels and can be generated with renewable energy without producing CO2. One way is solar-driven water-splitting. However, water-splitting via electrolysis is inefficient due to the overpotentials that arises. One of the causes for an increased overpotential originates from the bubbles that form when hydrogen and oxygen gases are formed. Therefore, it is important to understand the phenomena associate to the evolution of bubbles in the water-splitting reaction. To study the fundamentals of bubble evolution during electrolysis, we micromachine electrodes to have structures known to promote bubble nucleation. The modification allows an initial air pocket to be trapped in a cavity which functions as an artificial nucleation site on which we evolve bubbles. We will show the ongoing research in electrolyzers making use of artificial nucleation sites.

Electrical detection of single conducting polymers in liquid at open nanogap electrodes, Ab Nieuwenhuis (BE)

We propose a new transduction mechanism for the detection of individual molecular tags based on the detection of solvated conducting polymers in an open architecture without the need of intrinsic charge amplification. Here we demonstrate the electrical detection of single polymers in an organic solvent (Chloroform) in a 10 nm nanogap transducer.

We use several techniques to characterize the behavior of individual conducting polymers (Polythiophene, P3HT). Firstly, amperometric measurements reveal small discrete current steps of typically hundreds fA for a short duration (seconds)  when solvated polymers span the gap electrodes biased at a small potential difference of 20mV. We measure power spectra of the conducting polymers and determine the number and the mobility of the charge carriers using the Hooge model. Besides being electrically conductive when doped, these polymers become optically active when excited by blue light (480 nm). Their photoluminescence spectra peaking at wavelengths of ~600 nm enable us to localize polymers immobilized on the electrode surface. Fluorescence microscopy image reveals individual illuminating areas with sizes close to the diffraction limit (~350 nm) indicating single or a few polymers immobilized on the surface of the transducer. Furthermore dynamic light scattering technique returns a radius of gyration of ~8 nm for these polymers in solution, which is a size well suited to detect between 10 nm spaced electrodes. Finally,  preliminary AFM measurements show polymers immobilized on a HOPG monolayer surface with lengths comparable to the backbone length of a single polymer.

Towards a Miniaturized Wobbe Index Meter, Yiyuan Zhao (IDS)

An integrated Wobbe Index meter is desired in industries such as the central heating systems and fuel gas suppliers in many countries. Miniaturized on-chip fuel gas combustion and local temperature sensing facilitate the measurement of the Wobbe Index and determine the exchangeability of different fuel gases. State of the art studies on microscale combustion have reported that microflames suffer from flame extinction in microchannels. In the microchannels where the characteristic diameter is smaller than the critical quenching diameter, the huge surface-to-volume ratio induces thermal and radical quenching. However, excess enthalpy or heat recirculation in the Swiss Roll combustors can extend the flame flammability limit even under the quenching distance. Therefore, in order to optimize the microflames stability, we design microchannels with large internal volumes and integrated microheaters and temperature sensors. In this abstract we report our physics and fabrication considerations for designing a miniaturized on-chip combustion reactor.