Morten Hannibal Madsen, Nikolaj Agentoft Feidenhans'l, Poul-Erik Hansen, Jørgen Garnæs, Kai Dirscherl, Accounting for PDMS shrinkage when replicating structures, Journal of Micromechanics and Microengineering - 2014, Volume 24, Issue 12.

Abstract: Polydimethylsiloxane (PDMS) is a widely used material for fabrication of microfluidic devices and for replication of micro- and nanotextured surfaces. Shrinkage of PDMS in the fabrication process can lead to leaking devices and poor alignment of layers. However, corrections to the mold master are seldom applied to counteract the shrinkage of PDMS. Also, to perform metrological measurements using replica techniques one has to take the shrinkage into account. Thus we report a study of the shrinkage of PDMS with several different mixing ratios and curing temperatures. The shrinkage factor, with its associated uncertainty, for PDMS in the range 40 to 120 °C is provided. By applying this correction factor, it is possible to replicate structures with a standard uncertainty of less than 0.2% in lateral dimensions using typical curing temperatures and PDMS mixing ratios in the range 1:6 to 1:20 (agent:base).


Henrik Flyvbjerg, Commentary: How to get into that "room at the bottom”, Proc. Natl. Acad. Sci. (USA) 111, 13249-50 (2014).


Kasper Kistrupa, Karen Skotte Sørensena,b, Anders Wolffa, Mikkel Fougt Hansena, Liquid carry-over in an all-polymer chip system for immiscible phase magnetic bead-based solid phase extraction, Journal of Magnetism and Magnetic Materials, 2014.

Abstract: We present an all-polymer, single-use microfluidic chip system produced by injection moulding and bonded by ultrasonic welding. Both techniques are compatible with low-cost industrial mass-production.
The chip is produced for magnetic bead-based solid-phase extraction facilitated by immiscible phase filtration and features passive liquid filling and magnetic bead manipulation using an external magnet.In this work, We determine the system compatibility with various surfactants. Moreover, we quantify the volume of liquid co-transported with magnetic bead clusters from Milli-Q Water or alysis-binding buffer for nucleic acid extraction (0.1(v/v)% Triton X-100 in 5 M guanidine hydrochloride). A linear relationship was found between the liquid carry-over and mass of magnetic beads used. Interestingly, similar average carry-overs of 1.74(8) nL/mg and 1.72(14) nL/mg were found for Milli-Q Water and lysis-binding buffer, respectively.


Kasper Kistrup, Carl Esben Poulsen, Peter Friis Østergaard, Kenneth Brian Haugshøj, Rafael Taboryski, Anders Wolff, Mikkel Fougt Hansen, Fabrication and Modelling of Injection Moulded All-Polymer Capillary Microvalves for Passive Microfluidic Control, Journal of Micromechanics and Microengineering, 2014.

Abstract: Rapid prototyping is desirable when developing products. One example of such a product is all-polymer, passive flow controlled lab-on-a-chip systems that are preferential when
developing low-cost disposable chips for point-of-care use. In this paper we investigate the following aspects of going from rapid prototyping to pilot (mass) production. (1) Fabrication of an all-polymer microfluidic system using a rapid prototyped master insert for injection moulding and ultrasonic welding, including a systematic experimental characterisation of chip featured geometric capillary microvalve test structures. (2) Numerical modelling of the microvalve burst pressures. Numerical modelling of burst pressures is challenging due to its non-equilibrium nature. We have implemented and tested the level-set method modified with a damped driving term and show that the introduction of the damping term leads to numerically robust results with limited computational demands and a low number of iterations. Numerical and simplified analytical results are validated against the experimental results. We find that injection moulding and ultrasonic welding are effective for chip production and that the experimental burst pressures could be estimated with an average accuracy of 5% using the presented numerical model.


Christian L. Vestergaard, Paul C. Blainey, and Henrik Flyvbjerg, Optimal estimation of diffusion coefficients from single-particle trajectories, Phys. Rev. E 89, 022726 (2014) (31 pages).

Abstract: How does one optimally determine the diffusion coefficient of a diffusing particle from a single-time-lapse recorded trajectory of the particle? We answer this question with an explicit, unbiased, and practically optimal covariance-based estimator (CVE). This estimator is regression-free and is far superior to commonly used methods based on measured mean squared displacements. In experimentally relevant parameter ranges, it also outperforms the analytically intractable and computationally more demanding maximum likelihood estimator (MLE). For the case of diffusion on a flexible and fluctuating substrate, the CVE is biased by substrate motion.
However, given some long time series and a substrate under some tension, an extended MLE can separate particle diffusion on the substrate from substrate motion in the laboratory frame. This provides benchmarks that allow removal of bias caused by substrate fluctuations in CVE. The resulting unbiased CVE is optimal also for short time series on a fluctuating substrate. We have applied our estimators to human 8-oxoguanine DNA glycolase proteins diffusing on flow-stretched DNA, a fluctuating substrate, and found that diffusion coefficients are severely overestimated if substrate fluctuations are not accounted for.


Matteo Calaona, Hans N. Hansena, Guido Toselloa, Jørgen Garnaesb, Jesper Nørregaardc, Wei Lid, Microfluidic chip designs process optimization and dimensional quality control, Microsystem Technologies 2014.

Abstract: The challenge of fabricating geometries with critical dimensions ranging from few microns down to 10 nm with high production rate is delaying the development of nanotechnology based products. Diverse research works have shown the capability of technologies such as UV lithography, nano imprint lithography and e-beam lithography to produce micro and nano features. However, their application for tooling purposes is relatively new and the potential to produce nanometer features with high volume and low cost is enormous. Considering possible implementation in a mass production environment the precision of measuring results and the accuracy of measurement relocation are very relevant. In this paper, the capability of producing with high volume Lab-on-chip devices through injection molding is evaluated. Preparation of master geometries was made in a Si wafer using e-beam lithography and reactive ion etching. Subsequent nickel electroplating was employed to replicate the obtained geometries on the tool, which was used to mold on transparent polymer substrates the functional structures. To assess the critical factors affecting the replication quality throughout the different steps of the proposed process chain, test geometries were designed and produced on the side of the functional features. The so-called “Finger Print” of the lithography and molding processes was qualitatively and quantitatively evaluated through scanning electron microscopy and atomic force microscopy respectively. The entire process chain is therefore characterized and the degree of replication among the different replication steps quantified with precise measurements using a high accuracy relocation technique on the produced key test geometries. Influence of injection molding process parameters, feature dimensions and orientation relative to the polymer flow direction have been assessed in respect of the replication fidelity of the produced micro/sub-μm channels. Finally the paper addresses product compliance with specifications, focusing on tolerances of vertical dimensions using a metrological approach: sub-μm features on silicon, nickel stampers and injection molded substrates are measured. Results of measurement uncertainty calculation, quantitative replication fidelity assessment, and dimensional tolerances at the nanometer scale verification are reported.


Guido Toselloa, Hans Nørgaard Hansena, Matteo Calaona, and Stefania Gasparinb, Challenges in high accuracy surface replication for micro optics and micro fluidics manufacture, Int. J. Precision Technology, Vol. 4, Nos. 1/2, 2014.

Patterning the surface of polymer components with microstructured geometries is employed in optical and microfluidic applications. Mass fabrication of polymer micro structured products is enabled by replication technologies such as injection moulding. Micro structured tools are also produced by replication technologies such as nickel electroplating. All replication steps are enabled by a high precision master and high reproduction fidelity to ensure that the functionalities associated with the design are transferred to the final component. Engineered surface micro structures can be either distributed, e.g., to create an optical pattern, or discretised, e.g., as micro channels for fluids manipulation. Key aspects of two process chains based on replication technologies for both types of micro structures are investigated: lateral replication fidelity, dimensional control at micro scale, edge definition. The parts investigated are a micro retroreflector and a micro fluidic system, typical applications of injection moulded parts with micro structured functional surfaces.


Pétur Gordon Hermannsson, Christoph Vannahme, Cameron L. C. Smith, and Anders Kristensen, Absolute analytical prediction of photonic crystal guided mode resonance wavelengths, Applied Physics Letters 105, 071103 (2014).

Abstract: A class of photonic crystal resonant reflectors known as guided mode resonant filters are optical structures that are widely used in the field of refractive index sensing, particularly in biosensing. For the purposes of understanding and design, their behavior has traditionally been modeled numerically with methods such as rigorous coupled wave analysis. Here it is demonstrated how the absolute resonance wavelengths of such structures can be predicted by analytically modeling them as slab waveguides in which the propagation constant is determined by a phase matching condition. The model is experimentally verified to be capable of predicting the absolute resonance wavelengths to an accuracy of within 0.75 nm, as well as resonance wavelength shifts due to changes in cladding index within an accuracy of 0.45 nm across the visible wavelength regime in the case where material dispersion is taken into account. Furthermore, it is demonstrated that the model is valid beyond the limit of low grating modulation, for periodically discontinuous waveguide layers, high refractive index contrasts, and highly dispersive media.




K. Kistrup, K.S. Sørensen, P.F. Østergaard, R.J. Taboryski, A. Wolff, M.F. Hansen, All-polymer chip system for magnetic bead-based solid phase extraction, Poster presentation, EMBL Conference: Microfluidics 2014, Heidelberg, Germany, 2014.


C.E. Poulsen, K. Kistrup, N.K. Andersen, R.J. Taboryski, M.F. Hansen, A. Wolff, TransForm: Injection moulded 3D superhydrophobic surfaces, DTU Sustain, December 2014.


Theodor Nielsen, Participation in Conference exhibition in Tokyo – Presentation of NILT’s PolyNano results, Nano Tech conference (exhibition), Tokyo, January 2014.


Anders Kristensen, Christoph Vannahme, Petur G. Hermannsson, and Cameron L. C. Smith, Polymer Laser Bio-sensors, Invited paper, OSA  Optical Sensors, Barcelona 27-31 July, 2014.

Abstract: Organic dye based distributed feed-back lasers, featuring narrow linewidth and thus high quality spectral resolution, are used as highly sensitive refractive index sensors. The design, fabrication and application of the laser intra-cavity sensors are discussed.

M. Calaon, H.N. Hansen, G. Tosello, J. Garnaes, J. Nørregaard, W. Li, Process variations in surface nano geometries manufacture on large area substrates, Proceedings of the 14th euspen International Conference – Dubrovnik – June 2014

Abstract: The need of transporting, treating and measuring increasingly smaller biomedical samples has pushed the integration of a far reaching number of nanofeatures over large substrates size in respect to the conventional processes working area windows. Dimensional stability of nano fabrication processes over large area is key to ensure the device functionality. In this research, the process variation of sub-μm lithography processes is evaluated for different positions and features orientations, identified by produced test structures on a 100 mm diameter, 525 μm thick silicon wafer. The deviations from the target designed dimensions are quantified through AFM measurements on the silicon and on the subsequentely electroplated nickel geometries.


K. Kistrup, K.S. Sørensen, P.F. Østergaard, R. Taboryski, A. Wolff, M.F. Hansen, All-polymer system for magnetic bead-based solid phase extraction, Poster, EMBL Conference: Microfluidics 2014, Heidelberg, Germany 23-25 July 2014.


Kasper Kistrup, Karen Skotte Sørensen, Anders Wolff, Mikkel Fougt Hansen, Liquid carry-over in an all-polymer chip system for magnetic bead-based solid phase extraction, Poster, 10th International Conference on the Scientific and Clinical Applications of Magnetic Carriers, Dresden, Germany, 10-14 June 2014


Thor Christian Hobæk, Henrik Pranov, Niels B. Larsen, Direct Immobilization of Capture Antibodies on Injection Molded Plastics, Poster, Fourth International Workshop on Analytical Miniaturization and Nanotechnologies (WAM-NANO 2014), Copenhagen, Denmark, 23-24 June 2014



















































13 JUNE 2024