Dr. Ralph Stoop – Nanoscale Hybrid Electronic Systems

Research

Si-NW sensors

Publications

2017

Charge Noise in Organic Electrochemical Transistors
Stoop, Ralph L., Kishan Thodkar, Michele Sessolo, Henk J. Bolink, Christian Schoenenberger, and Michel Calame.
Phys. Rev. Applied, 7, 14009 (2017).

2016

Active Surfaces as Possible Functional Systems in Detection and Chemical (Bio) Reactivity
Housecroft, Catherine E., Cornelia G. Palivan, Karl Gademann, Wolfgang Meier, Michel Calame, Viktoria Mikhalevich, Xiaoyan Zhang, Ellen Piel, and Mathieu Szponarski, et al.
Chimia, 70 (6), 402-412 (2016).
[Abstract]

This article presents design strategies to demonstrate approaches to generate functionalized surfaces which have the potential for application in molecular systems; sensing and chemical reactivity applications are exemplified. Some applications are proven, while others are still under active investigation. Adaptation and extension of our strategies will lead to interfacing of different type of surfaces, specific interactions at a molecular level, and possible exchange of signals/cargoes between them. Optimization of the present approaches from each of five research groups within the NCCR will be directed towards expanding the types of functional surfaces and the properties that they exhibit.
Implementing Silicon Nanoribbon Field-Effect Transistors as Arrays for Multiple Ion Detection
Stoop, Ralph L., Mathias Wipf, Steffen Mueller, Kristine Bedner, Iain A. Wright, Colin J. Martin, Edwin C. Constable, Axel Fanget, and Christian Schoenenberger, et al.
Biosensors, 6 (2), 21 (2016).
[Abstract]

Ionic gradients play a crucial role in the physiology of the human body, ranging from metabolism in cells to muscle contractions or brain activities. To monitor these ions, inexpensive, label-free chemical sensing devices are needed. Field-effect transistors (FETs) based on silicon (Si) nanowires or nanoribbons (NRs) have a great potential as future biochemical sensors as they allow for the integration in microscopic devices at low production costs. Integrating NRs in dense arrays on a single chip expands the field of applications to implantable electrodes or multifunctional chemical sensing platforms. Ideally, such a platform is capable of detecting numerous species in a complex analyte. Here, we demonstrate the basis for simultaneous sodium and fluoride ion detection with a single sensor chip consisting of arrays of gold-coated SiNR FETs. A microfluidic system with individual channels allows modifying the NR surfaces with self-assembled monolayers of two types of ion receptors sensitive to sodium and fluoride ions. The functionalization procedure results in a differential setup having active fluoride- and sodium-sensitive NRs together with bare gold control NRs on the same chip. Comparing functionalized NRs with control NRs allows the compensation of non-specific contributions from changes in the background electrolyte concentration and reveals the response to the targeted species.
Label-Free FimH Protein Interaction Analysis using Silicon Nanoribbon BioFETs
Wipf, Mathias, Ralph L. Stoop, Giulio Navarra, Said Rabbani, Beat Ernst, Kristine Bedner, Christian Schoenenberger, and Michel Calame.
ACS Sensors, 1 (6), 781–788 (2016).
[Abstract]

The detection of biomarkers at very low concentration and low cost is increasingly important for clinical diagnosis. Moreover, monitoring affinities for receptor-antagonist interactions by time-resolved measurements is crucial for drug discovery and development. Biosensors based on ion-sensitive field-effect transistors (BioFETs) are promising candidates for being integrated into CMOS structures and cost-effective production. The detection of DNA and proteins with silicon nanowires has been successfully demonstrated using high affinity systems such as the biotin–streptavidin interaction. Here, we show the time-resolved label-free detection of the interaction of the bacterial FimH lectin with an immobilized mannose ligand on gold-coated silicon nanoribbon BioFETs. By comparing our results with a commercial state of the art surface plasmon resonance system, additional surface effects become visible when using this charge based detection method. Furthermore, we demonstrate the effect of sensor area on signal-to-noise ratio and estimate the theoretical limit of detection.

2015

Sensing with Advanced Computing Technology: Fin Field Effect Transistors with High-K Gate Stack on Bulk Silicon
Rigante, Sara, Paolo Scarbolo, Mathias Wipf, Ralph L. Stoop, Kristine Bedner, Elizabeth Buitrago, Antonios Bazigos, Didier Bouvet, and Michel Calame, et al.
ACS Nano, 9 (5), 4872-4881 (2015).
Competing Surface Reactions Limiting the Performance of Ion-Sensitive Field-Effect Transistors
Stoop, Ralph L., Mathias Wipf, Steffen Mueller, Kristine Bedner, Iain A. Wright, Colin J. Martin, Edwin C. Constable, Wangyang Fu, and Alexey Tarasov, et al.
Sensors and Actuators B, 220, 500-507 (2015).

2014

Investigation of the dominant 1/f Noise Source in Silicon Nanowire Sensors
Bedner, K., V. A. Guzenko, A. Tarasov, M. Wipf, R. Stoop, S. Rigante, J. Brunner, W. Fu, and C. David, et al.
Sensors and Actuators B, 191, 270-275 (2014).
Sensor system including silicon nanowire ion sensitive FET arrays and CMOS readout
Livi, Paolo, Amir Shadmani, Mathias Wipf, Ralph L. Stoop, Joerg Rothe, Yihui Chen, Michel Calame, Christian Schoenenberger, and Andreas Hierlemann.
Sensors and Actuators B: Chemical, 204, 568-577 (2014).

2013

pH- Response of Silicon Nanowire Sensors: Impact of Nanowire Width and Gate Oxide
Bedner, K., V. A. Guzenko, A. Tarasov, M. Wipf, R. L. Stoop, D. Just, S. Rigante, W. Fu, and R. A. and Minamisawa, et al.
Sensors and Materials, 25 (8), 567-576 (2013).
High mobility graphene ion-sensitive field-effect transistors by noncovalent functionalization
Fu, W., C. Nef, A. Tarasov, M. Wipf, R. Stoop, O. Knopfmacher, M. Weiss, M. Calame, and C. Schoenenberger.
Nanoscale, 5, 12104-12110 (2013).
Selective Sodium Sensing with Gold-Coated Silicon Nanowire Field-Effect Transistors in a Differential Setup
Wipf, Mathias, Ralph L. Stoop, Alexey Tarasov, Kristine Bedner, Wangyang Fu, Iain A. Wright, Colin J. Martin, Edwin C. Constable, and Michel Calame, et al.
ACS Nano, 7 (7), 5978-5983 (2013).
Wipf, M., R. L. Stoop, A. Tarasov, K. Bedner, W. Fu, M. Calame, and C. Schönenberger. Potassium sensing with membrane-coated silicon nanowire field-effect transistors. , Proceeding of the 17th IEEE International Conference on Solid-State Sensors, Actuators & Microsystems (Transducers & Eurosensors XXVII), Barcelona, Spain, 16-20 June 2013, pages 1182-1185, 2013.

2012

Understanding the Electrolyte Background for Biochemical Sensing with Ion-Sensitive Field-Effect Transistors
Tarasov, A., M. Wipf, K. Bedner, J. Kurtz, Wangyang Fu, Vitaliy A. Guzenko, Oren Knopfmacher, Ralph L. Stoop, and Michel Calame, et al.
ACS Nano, 6 (10), 9291-9298 (2012).
A True Reference Nanosensor Realized with Silicon Nanowires
Tarasov, A., M. Wipf, K. Bedner, J. Kurtz, Wangyang Fu, Vitaliy A. Guzenko, Oren Knopfmacher, Ralph L. Stoop, and Michel Calame, et al.
Langmuir, 28 (25), 9899-9905 (2012).
[Abstract]

Conventional gate oxide layers (e.g., SiO2, Al2O3, or HfO2) in silicon field-effect transistors (FETs) provide highly active surfaces, which can be exploited for electronic pH sensing. Recently, great progress has been achieved in pH sensing using compact integrateable nanowire FETs. However, it has turned out to be much harder to realize a true reference electrode, which – while sensing the electrostatic potential – does not respond to the proton concentration. In this work, we demonstrate a highly effective reference sensor, a so-called reference FET, whose proton sensitivity is suppressed by as much as 2 orders of magnitude. To do so, the Al2O3 surface of a nanowire FET was passivated with a self-assembled monolayer of silanes with a long alkyl chain. We have found that a full passivation can be achieved only after an extended period of self-assembling lasting several days at 80 °C. We use this slow process to measure the number of active proton binding sites as a function of time by a quantitative comparison of the measured nonlinear pH-sensitivities to a theoretical model (site-binding model). Furthermore, we have found that a partially passivated surface can sense small changes in the number of active binding sites reaching a detection limit of ?Ns ? 170 ?m–2Hz–1/2 at 10 Hz and pH 3.
Fu, Wangyang, Cornelia Nef, Alexey Tarasov, Mathias Wipf, Ralph Stoop, Oren Knopfmacher, Markus Weiss, Michel Calame, and Christian Schoenenberger. Sensing with liquid-gated graphene field-effect transistors. In Nanotechnology (IEEE-NANO), Nanotechnology (IEEE-NANO). IEEE; IEEE Nanotechnol Council; Univ Birmingham; Inst Phys (IOP),, 2012. 12th IEEE International Conference on Nanotechnology (IEEE-NANO), Birmingham, ENGLAND, AUG 20-23, 2012
[Abstract]

Liquid-gated graphene field-effect transistors (GFETs) with reliable performance are developed. It is revealed that ideal defect-free graphene should be inert to electrolyte composition changes in solution, whereas a defective one responses to electrolyte composition. This finding sheds light on the large variety of pH or ion-induced gate shifts that have been published for GFETs in the recent literature. As a next step to target graphene-based (bio-) chemical sensing platform, non-covalent functionalization of graphene has to be introduced.