Ted Limpoco (Oxford Instruments)

We have developed the first commercial atomic force microscope to use quadrature phase differential interferometry (QPDI) which greatly improves the accuracy and precision of AFM measurements. This is not the first AFM to use interferometric sensing. Several early implementations were abandoned because of their complexity, limited measurement range, and poor low-frequency noise performance. When optical beam deflection (OBD) was introduced in 1988, it became the standard AFM detection system until today.​

Sibel Ebru Yalcin (Yale)

Deep in the ocean or underground, where there is no oxygen, Geobacter “breathes” by projecting tiny hair-like protein filaments called "nanowires" into the soil to dispose of excess electrons resulting from converting nutrients to energy and cleaning up radioactive sites. Although it is long known that Geobacter uses filaments for electron transfer (Nature 2002, 2005), it is not clear what they are actually made of and why they are conductive.

Our studies have revealed a surprise: the nanowires have a core of hemes lining up to create a continuous path along which electrons travel (Cell’19, Nature Chem.Bio.’20, Nature Micro.­’23) and and can be engineered with atomic precision using recombinant DNA technology, making for remarkably versatile electronic components.

We have further found that Geobacter pili remain hidden inside the cell and serve as a piston to secrete nanowire-forming cytochromes (Nature 2021) rather than functioning as a nanowire themselves as previously thought (Current Opinion 2020).

These studies solve a longstanding mystery to explain our previous findings that these bacteria transport electrons via nanowires (Nature Nano. 2014) over 100-times their size to electron acceptors (Nature Nano. 2011) and partner cells (Science 2010) and store electrons when acceptors are absent akin to how humans use their lungs (ChemPhysChem 2012) .

Our contact-free measurements of intrinsic electron conductivity in individual protein nanowires reveal how energetics and proximity of proton acceptors modulate conductivity by 100-fold (PNAS 2021, Biochem. Journal 2021). We have also developed synthetic protein nanowires with tunable conductivity and programmable self-assembly using non-natural click-chemistry functionality (Nature Comm. 2022).

In this talk I will present our efforts to identify the physical and molecular mechanism of high conductivity of microbial cytochrome nanowires. Our conducting-probe AFM measurements show one of the highest electronic conductivity ever reported in proteins (> 100 S/cm) (Nature Chem.Bio.’20). Femtosecond transient absorption spectroscopy and quantum dynamics simulations reveal ultrafast (<200 fs) electron transfer between nanowire hemes upon photoexcitation, enhancing carrier density and mobility. Photoconductive atomic force microscopy shows up to 100-fold increase in photocurrent in purified individual nanowires. Photocurrents respond rapidly (<100 ms) to the excitation and persist reversibly for hours (Nature Comm.’22). Furthermore, nanowires and biofilms show non-classical temperature dependence of conductivity with cooling accelerating electron transport by 300-fold (Science Adv.).

Computations yielded up to a billion-fold lower conductivity than experiments (JPCB’21, JPCB’22), illustrating that the hopping assumption fails to capture electron transfer in biological nanowires. This raises the possibility that biological nanowires employ a fundamentally different, currently unknown mechanism. Thus, existing models predict the same conductivity for all nanowires with computed timescales for heme-to-heme electron transfers (100 ns), million-fold lower than that measured using transient absorption in excited-state (Nature Comm.’22) and conductivity in ground-state for fully hydrated (Nature & Cell) or air-dried nanowires (Science Adv.).

Notably, multiple computational studies have predicted that invoking quantum effects could account for the high conductivity of these nanowires (Nanotechology’20, IEEE’21, ACS Nano’23). I will present our recent efforts to experimentally assess these computational predictions using multiple probes such as light, temperature, electric and magnetic fields. I will also discuss how our studies are helping to understand, predict, and control electron transfer by nanowires used by diverse environmental microbes to capture, convert, and store energy (Nature Comm.’24 #1 & #2)

Robb Westby (Oxford Instruments)

Microanalysis, the characterization of materials at a microscopic scale, has witnessed remarkable advancements in recent years. This talk explores key techniques that have pushed the boundaries of microanalytical capabilities. Energy Dispersive X-ray Spectroscopy, a cornerstone of materials characterization, has evolved from a curiosity to quantitative elemental analysis and a nanoscale. Electron backscatter Kikuchi pattern (EBSD) analysis has emerged as a powerful tool for crystallographic orientation mapping, first pioneered from beer cans, to providing insights into meso and nanograin boundaries, texture, and deformation mechanisms. Nanoindentation, a technique for measuring mechanical properties at the nanoscale, has been refined with the development of sophisticated instrumentation for both speed and sensitivity for data analysis. By combining these techniques, researchers can now probe the microstructure and properties of materials with unprecedented precision, leading to breakthroughs in fields such as materials science, engineering, and nanotechnology.

Adam Wise (Oxford Instruments)

Cameras with integrated, gateable image intensifiers – like the Andor iStar - are capable of nanosecond-scale time resolution and single photon sensitivity over a wide range of wavelengths, from the ultraviolet to near-infrared. This combination finds use in diverse fields including quantum optics, materials science, combustion, fusion, and biological imaging. We will present a brief review of how intensified cameras work, show how they can be integrated with common imaging and spectroscopy setups, and present recent, exciting work showcasing their unique performance, particularly in photophysical characterization of energy materials. Special attention will be paid to practical experimental considerations. Join us afterwards for a hands-on experience with intensified cameras for imaging and spectroscopy.

Prof. Viktoriia Rutckaia (CUNY ASRC)

This talk presents the study of photonic bound states in the continuum (BIC) in silicon-based metasurfaces, focusing on their transmission characteristics. By leveraging the unique properties of BICs, which exhibit localized electromagnetic modes despite existing within the continuum of radiation states, we explore the design and fabrication of Si metasurfaces to achieve high-Q resonances. The transmission measurements provide insights into the coupling mechanisms and potential applications of BICs in integrated photonic devices, such as sensors, filters, and modulators.