Multi-pass transmission electron microscopy

Abstract

Feynman once asked physicists to build better electron microscopes to be able to watch biology at work. While electron microscopes can now provide atomic resolution, electron beam induced specimen damage precludes high resolution imaging of sensitive materials, such as single proteins or polymers. Here, we use simulations to show that an electron microscope based on a multi-pass measurement protocol enables imaging of single proteins, without averaging structures over multiple images. While we demonstrate the method for particular imaging targets, the approach is broadly applicable and is expected to improve resolution and sensitivity for a range of electron microscopy imaging modalities, including, for example, scanning and spectroscopic techniques. The approach implements a quantum mechanically optimal strategy which under idealized conditions can be considered interaction-free.

Label-free single-instance protein detection in vitrified cells

“…The need for only a single un-tilted image greatly simplifies acquisition and makes cHRTM compatible with pulsed-beam (Spence 2017) and multi-pass imaging techniques (Juffmann et al 2017;Koppell et al 2019), both designed to increase the amount of highresolution information extracted before it is lost to radiation damage. Together with improved detectors, this might well boost the sensitivity of cHRTM enough to make the majority of proteins detectable.…”

Full-field cavity enhanced microscopy techniques

“…This interferometric advantage is due to the coherent amplification of the intra-cavity field amplitudes that are transmitted and reflected by the sample in the CW case. Even in the limit of T 1 →1, we find that the linear sample response differs by a factor of two between the CW output field (13) and the first output pulse in (14). The CW advantage comes with the experimental difficulty of Figure 4.…”

“…The glass plate induces an effective phase shift 2kd g between the left-and right-running components that not only shifts the cavity resonance, but also modulates the reflections at the sample layer, as seen explicitly in (14). In the pulsed imaging schemes discussed below, this will mainly affect the samplereflected pulses outcoupled after an even number of sample interactions, see (26).…”

“…In particular, the zeros in (c) are where the total phase shift assumes multiples of π. So the WS expressions (14) for the output field and (25), (31), (33) for the detection signals (derived under the assumption c  | | m 1) are not valid. Nevertheless, the single-pass phase shift c =´-7.4 10 2 is still small, which allows us to use (6) and expand the eigenvalues λ ± that determine the relative weight of the mth pass in the output field (11).…”

“…photo-thermal damage of pigmented cells [10], UV induced breaking of DNA strands [11,12], single-or multi-photon absorption followed by cytotoxic photochemical reactions [10,13]). MP microscopy has also been proposed for transmission electron microscopy [14], where sample damage sets bounds on the obtainable spatial resolution [15].…”