König, K.

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Microparticle transfer onto pixel electrodes of 45 μm pitch on HV-CMOS chips - Simulation and experiment
(2011-12-01)
Wagner, J.
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König, K.
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Foertsch, Tobias C.
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Löffler, F.
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Fernandez, S.
Spatially selective deposition of electrically charged microparticles onto integrated circuits that generate electrical fields in programmable patterns using electrodes on their surface was previously limited to a pixel pitch of 100 μm. Now, we demonstrate spatially selective deposition onto pixels of 45 μm pitch in experiments on a test chip allowing arbitrary patterns, but being of limited size and of fixed characteristics, complemented by COMSOL simulations. Experiments on a prototype high voltage CMOS chip demonstrate the feasibility of miniaturisation in the first place, imply simulations of interest that cannot be tested experimentally and, conversely, complement the simplified simulation models by reality checks. Using COMSOL for the optimisation of the setup parameters, particles of decreasing average diameter in a number of aerosol and electrical field geometries are simulated with particular attention to minimising contamination (deposition of particles on undesirable locations). Combining these results, the average particle diameter is decreased from 10 μm to less than 3 μm and the deposition voltage is reduced from 100 V to 30 V, when using pixels with a pitch of 45 μm. Optimising these parameters allows for more than quadrupling the spot density compared to the previous chip, on which combinatorial particle deposition with minimal contamination is achieved. Peptide arrays, having been previously shown to be a major application for this method, benefit in particular, as the increase in density from 10,000 pixels/cm2 to approximately 50,000 pixels/cm2 promises a significant decrease in cost-per-peptide and amount of test specimens required.
Publicationtype: Journal Article
7
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High-precision combinatorial deposition of micro particle patterns on a microelectronic chip
(2011-01-01)
Loeffler, Felix F.
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Wagner, J.
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Konig, K.
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Markle, F.
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Fernandez, S.
The behavior of charged bio polymer micro particles when deposited onto a CMOS chip can be analytically modeled in form of the incompressible Navier-Stokes equation and the electrostatic Poisson equation, as we describe in this article. Based on these models, numerical simulations of depositions can be implemented in COMSOL that lead to improvements in the experimental setup, optimizing the size and charge distribution of the micro particles. Adapting the experiments according to the simulation results, we will show the powerful gain in deposition precision, which is essential for a contamination-free deposition and hence high quality combinatorial deposition.
Publicationtype: Journal Article
4
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Quality analysis of selective microparticle deposition on electrically programmable surfaces
(2010-07-01)
Wagner, J.
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Löffler, F.
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König, K.
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Fernandez, S.
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Nesterov-Müller, Alexander
Image processing and pattern analysis can evaluate the deposition quality of triboelectrically charged microparticles on charged surfaces. The image processing method presented in this paper aims at controlling the quality of peptide arrays generated by particle based solid phase Merrifield combinatorial peptide synthesis. Incorrectly deposited particles are detected before the amino acids therein are coupled to the growing peptide. The calibration of the image acquisition is performed in a supervised training step in which all parameters of the quality analyzing algorithm are learnt given one representative image. Then, the correct deposition pattern is determined by a linear support vector machine. Knowing the pattern, contaminated areas can be detected by comparing the pattern with the actual deposition. Taking into account the resolution of the image acquisition system and its magnification factor, the number and size of contaminating particles can be calculated out of the number of connected foreground pixels. © 2010 American Institute of Physics.
Publicationtype: Journal Article
8
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Programmable high voltage CMOS chips for particle-based high-density combinatorial peptide synthesis
(2010-06-03)
König, K.
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Block, I.
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Nesterov-Mueller, Alexander
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Torralba, G.
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Fernandez, S.
We built high voltage complementary metal oxide semiconductor (CMOS) chips that generate electrical fields on their surface, such that electrically charged microparticles (diameter 10-20 μm on average) can be addressed on distinct pixel electrodes according to arbitrary field patterns. Each pixel contains a memory cell in canonical low-voltage CMOS-technology controlling a high voltage (30-100 V) potential area on the top metal layer. Particle transfer with minimal contaminations in less than 10 s for a complete chip was observed for pixels of 100 μm × 100 μm down to 65 μm × 65 μm. This allows a new way to create surface modifications on top of CMOS chips without need for additional masks or stamps. Using suitable particles, a chemically modified chip surface, and compatible chemistry, this method can be utilized for self-aligned high-density biopolymer arrays, e.g., peptide arrays. Transfer of microparticles loaded with amino acids for combinatorial peptide synthesis is demonstrated. Successful synthesis of different peptides (octamers) was proven by immunostaining. Based on results obtained by a chip containing pixel areas of different characteristics, a chip for biological applications with 16,384 pixels (10,000 pixel/cm2) was built. Good homogeneity of peptide synthesis over the chip area was verified by immunostaining. © 2010 Elsevier B.V. All rights reserved.
Publicationtype: Journal Article
7
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Characterization of triboelectrically charged particles deposited on dielectric surfaces
(2010-04-22)
Nesterov, A.
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Loeffler, Felix F.
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Cheng, Yun Chien
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Torralba, G.
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König, K.
A device for the measurement of q/m-values and charge degradation of triboelectrically charged particles deposited on a surface was developed. The setup is based on the integration of currents, which are induced in a Faraday cage by insertion of a solid support covered with charged particles. The conductivity of different particle supports was taken into account. The 'blow-off' method, in which the particles are first deposited, and then blown off using an air stream, can be used for characterization of triboelectric properties of particles relative to different surfaces. © 2010 IOP Publishing Ltd.
Publicationtype: Journal Article
4
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Measurement of triboelectric charging of moving micro particles by means of an inductive cylindrical probe
(2007-10-07)
Nesterov, A.
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Löffler, F.
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König, K.
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Trunk, U.
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Leibe, K.
We present a method based on induced currents in a cylindrical probe which allows analysis of the micro-particle charging processes in an aerosol. The micro particles were triboelectrically charged by passing through a dielectric tube coaxially mounted into the probe. The cylindrical probe enabled the quantification of particle charging without prior calibration of the probe. An analytic model was developed for the description of the measured induced currents and implemented into a computer simulation program. The combination of model simulations and an appropriate experimental setup revealed comprehensive data for the determination of the particles' electric charge against time of flight through the tube. In methodological proof of principle experiments, the formations of particle clouds with charges of different signs were observed using magnetite micro particles. © 2007 IOP Publishing Ltd.
Publicationtype: Journal Article
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