Pawel Utko

Confinement Spectroscopy: Probing Single DNA Molecules with Tapered Nanochannels

We demonstrate a confinement spectroscopy technique capable of probing small conformational changes of unanchored single DNA molecules in a manner analogous to force spectroscopy, in the regime corresponding to femtonewton forces. In contrast to force spectroscopy, various structural forms of DNA can easily be probed, as indicated by experiments on linear and circular DNA. The extension of circular DNA is found to scale according to the de Gennes exponent, unlike for linear DNA.

Intact Mammalian Cell Function on Semiconductor Nanowire Arrays: New Perspectives for Cell‐Based Biosensing

Nanowires (NWs) are attracting more and more interest due to their potential cellular applications, such as delivery of compounds or sensing platforms. Arrays of vertical indium-arsenide (InAs) NWs are interfaced with human embryonic kidney cells and rat embryonic dorsal root ganglion neurons. A selection of critical cell functions and pathways are shown not to be impaired, including cell adhesion, membrane integrity, intracellular enzyme activity, DNA uptake, cytosolic and membrane protein expression, and the neuronal maturation pathway. The results demonstrate the low invasiveness of InAs NW arrays, which, combined with the unique physical properties of InAs, open up their potential for cellular investigations.

Injection molded chips with integrated conducting polymer electrodes for electroporation of cells

We present the design-concept for an all polymer injection molded single use microfluidic device. The fabricated devices comprise integrated conducting polymer electrodes and Luer fitting ports to allow for liquid and electrical access. A case study of low voltage electroporation of biological cells in suspension is presented. The working principle of the electroporation device is based on a focusing of the electric field by means of a constriction in the flow channel for the cells. We demonstrate the use of AC voltage for electroporation by applying a 1 kHz, ±50 V square pulse train to the electrodes and show delivery of polynucleotide fluorescent dye in 46% of human acute monocytic leukemia cells passing the constriction.

Sub-Kelvin transport spectroscopy of fullerene peapod quantum dots

The authors have studied electrical transport properties of individual C60 fullerene peapods, i.e., single-wall carbon nanotubes encapsulating C60 molecules. Their measurements indicated power lawlike temperature dependencies of linear conductance similar to those for empty nanotubes. At temperatures below 30K, peapod devices behaved as highly regular individual quantum dots showing regular Coulomb blockade oscillations. Signatures of Kondo physics appeared at the lowest measurement temperature of 315mK.

Heating in single-electron pumps driven by surface acoustic waves

We use a practical thermometer based on the resistance of the two-dimensional electron gas to characterize single-electron devices driven by surface acoustic waves. At the typical microwave powers (∼10dBm) required to observe the quantization of the acoustoelectric current in such structures, the electron-gas temperature increases from our base 1.8Kto5–6K. The power deposited by the surface acoustic wave itself can be clearly resolved. However, it is several times smaller than the overall rf heating, which occurs over a frequency range of few gigahertz.

The influence of electro-mechanical effects on resonant electron tunneling through small carbon nano-peapods

The influence of a fullerene molecule trapped inside a single-wall carbon nanotube on resonant electron transport at low temperatures and strong polaronic coupling is theoretically discussed. Strong peak-to-peak fluctuations and anomalous temperature behavior of conductance amplitudes are predicted and investigated. The influence of the chiral properties of carbon nanotubes on transport is also studied.