Single-Nanoparticle Thermometry with a Nanopipette

Thermal measurements at the nanoscale are key for designing technologies in many areas, including drug delivery systems, photothermal therapies, and nanoscale motion devices. Herein, we present a nanothermometry technique that operates in electrolyte solutions and, therefore, is applicable for many in vitro measurements, capable of measuring and mapping temperature with nanoscale spatial resolution and sensitive to detect temperature changes down to 30 mK with 43 μs temporal resolution. The methodology is based on local measurements of ionic conductivity confined at the tip of a pulled glass capillary, a nanopipettete, with opening diameters as small as 6 nm. When scanned above a specimen, the measured ion flux is converted into temperature using an extensive theoretical support given by numerical and analytical modeling. This allows quantitative thermal measurements with a variety of capillary dimensions and is applicable to a range of substrates. We demonstrate the capabilities of this nanothermometry technique by simultaneous mapping of temperature and topography on sub-micrometer-sized aggregates of thermoplasmonic nanoparticles heated by a laser and observe the formation of micro- and nanobubbles upon plasmonic heating. Furthermore, we perform quantitative thermometry on a single-nanoparticle level, demonstrating that the temperature at an individual nanoheater of 25 nm in diameter can reach an increase of about 3 K.

Wearable System for Simultaneous Online Imaging and Noninvasive Neuromodulation

Neuromodulation is the interfacing and intervening with nervous with the aim of long-term modification and/or regulation of neural activity. To date, neuromodulation has been used to treat various pathologies of the nervous system including epilepsy, stroke and addiction, among others. In spite of its numerous applications, the underlying mechanisms of neuromodulation are not well understood.

In this study, we present a system for joint online neuroimaging and neuromodulation in real world settings. We combine tDCS (transcranial direct current stimulation) and fNIRS (functional near infrared spectroscopy) and optimize the system in terms of size, number and placement of electrodes to achieve focal stimulation without off-site effects. We discuss and evaluate battery life, portability and ergonomics of the device. We further present an algorithm for closed-loop stimulation based on online hemodynamic recordings. Both the device and the algorithm are to our knowledge novel and represent a contribution to understanding how neuromodulation therapies interact with complex neural circuitry and how this leads to behavioral outcomes. The presented system is not only a powerful research tool but paves the way to personalized, at-home therapy of neural disorders.

publications

journals

• Holub, M., Adobes-Vidal, M., Frutiger, A., Gschwend, P. M., Pratsinis, S. E., & Momotenko, D. (2020). Single-nanoparticle thermometry with a nanopipette. ACS nano, 14(6), 7358-7369. (link)
• Fisch, P., Holub M., and Zenobi-Wong, M. “Improved Accuracy and Precision of Bioprinting through Progressive Cavity Pump-Controlled Extrusion.” Preprint. Bioengineering, January 24, 2020. (link)
• Hrdy, R.; Kynclova, H.; Klepacova, I.; Bartosik, M.; Neuzil, P. Portable Lock-in Amplifier-Based Electrochemical Method to Measure an Array of 64 Sensors for Point-of-Care Applications. ANALYTICAL CHEMISTRY, 2017, 86(17), 8731-8737. (link)
  • Contributed to the publication as an undergraduate researcher at CEITEC (Central European Institute of Technology)

conference posters & talks

• Fisch, P., Holub, M., Zenobi-Wong, M. (2017). Comparison of Printing Accuracy of Screw- vs. Press-Driven Extrusion of Bioinks. International conference on biofabrication, Beijing: 2017
• Jedelský, J.; Malý, M.; Holub, M.; Jícha, M. (2015). Some Aspects of Disintegration of Annular Liquid Sheet in Pressure- Swirl Atomization. In Conference on Modelling Fluid Flow. Budapest: 2015. s. 1-8. ISBN: 978-963-313-190- 9.

theses

• Holub, M. (2019) Scanning Nanopipette Thermometry; Master thesis; ETH Zürich, Switzerland
• Holub, M. (2017) A Novel Extrusion System for Bioprinting; Semester project, ETH Zürich, Switzerland
• Holub, M. (2016). Cavitation in Microfluidics (link); Bachelor thesis; BUT, Brno, Czech Republic