Wah-Keat Lee

Butterfly proboscis: combining a drinking straw with a nanosponge facilitated diversification of feeding habits

The ability of Lepidoptera, or butterflies and moths, to drink liquids from rotting fruit and wet soil, as well as nectar from floral tubes, raises the question of whether the conventional view of the proboscis as a drinking straw can account for the withdrawal of fluids from porous substrates or of films and droplets from floral tubes. We discovered that the proboscis promotes capillary pull of liquids from diverse sources owing to a hierarchical pore structure spanning nano- and microscales. X-ray phase-contrast imaging reveals that Plateau instability causes liquid bridges to form in the food canal, which are transported to the gut by the muscular sucking pump in the head. The dual functionality of the proboscis represents a key innovation for exploiting a vast range of nutritional sources. We suggest that future studies of the adaptive radiation of the Lepidoptera take into account the role played by the structural organization of the proboscis. A transformative two-step model of capillary intake and suctioning can be applied not only to butterflies and moths but also potentially to vast numbers of other insects such as bees and flies.

Mechanistic origins of bombardier beetle (Brachinini) explosion-induced defensive spray pulsation

A beetles internal bomb Bombardier beetles shoot a toxic pulse at potential predators and other harassers. The toxic spray is created by a chemical reaction that occurs inside the beetles body. Although the details of the reaction are known, how the beetle is able to precisely combine the chemicals at appropriate times and release the pulse at regular intervals has remained a mystery. Arndt et al. used synchrotron x-ray imagery to observe the process as it occurs within live beetles. Expansion and contraction of an internal expansion membrane facilitate the precise cyclic injection of reactants and the subsequent ejection of toxic sprays that keep the beetles predators at bay. Science, this issue p. 563 Bombardier beetles use internal pulsed chemical reactions to deter prey. Bombardier beetles (Brachinini) use a rapid series of discrete explosions inside their pygidial gland reaction chambers to produce a hot, pulsed, quinone-based defensive spray. The mechanism of brachinines’ spray pulsation was explored using anatomical studies and direct observation of explosions inside living beetles using synchrotron x-ray imaging. Quantification of the dynamics of vapor inside the reaction chamber indicates that spray pulsation is controlled by specialized, contiguous cuticular structures located at the junction between the reservoir (reactant) and reaction chambers. Kinematics models suggest passive mediation of spray pulsation by mechanical feedback from the explosion, causing displacement of these structures.

Sharpening the surface of magnetic paranematic droplets

In a non-uniform magnetic field, the droplets of colloids of nickel nanorods and nanobeads aggregate to form a cusp at the droplet surface not deforming the entire droplet shape. When the field is removed, nanorods diffuse away and the cusp disappears. Spherical particles can form cusps in a similar way, but they stay aggregated after the release of the field; finally, the aggregates settle down to the bottom of the drop. The X-ray phase contrast imaging reveals that nanorods in the cusps stay parallel to each other without visible spatial order of their centers of mass. The formation of cusps can be explained with a model that includes magnetostatic and surface tension forces. The discovered possibility of controlled assembly and quenching of nanorod orientation under the cusped liquid surface offers vast opportunities for alignment of carbon nanotubes, nanowires and nanoscrolls, prior to spinning them into superstrong and multifunctional fibers. Magnetostatic and electrostatic analogies suggest that a similar ideal alignment can be achieved with the rod-like dipoles subject to a strong electric field.

PyXRF: Python-based X-ray fluorescence analysis package

We developed a python-based fluorescence analysis package (PyXRF) at the National Synchrotron Light Source II (NSLS-II) for the X-ray fluorescence-microscopy beamlines, including Hard X-ray Nanoprobe (HXN), and Submicron Resolution X-ray Spectroscopy (SRX). This package contains a high-level fitting engine, a comprehensive commandline/ GUI design, rigorous physics calculations, and a visualization interface. PyXRF offers a method of automatically finding elements, so that users do not need to spend extra time selecting elements manually. Moreover, PyXRF provides a convenient and interactive way of adjusting fitting parameters with physical constraints. This will help us perform quantitative analysis, and find an appropriate initial guess for fitting. Furthermore, we also create an advanced mode for expert users to construct their own fitting strategies with a full control of each fitting parameter. PyXRF runs single-pixel fitting at a fast speed, which opens up the possibilities of viewing the results of fitting in real time during experiments. A convenient I/O interface was designed to obtain data directly from NSLS-II’s experimental database. PyXRF is under open-source development and designed to be an integral part of NSLS-II’s scientific computation library.

The butterfly proboscis as a fiber-based, self-cleaning, micro-fluidic system

The butterfly proboscis is a unique, naturally engineered device for acquiring liquid food, which also minimizes concerns for viscosity and stickiness of the fluids. With a few examples, we emphasize the importance of the scale-form functionality triangle of this feeding device and the coupling through capillarity.

FXI: a full-field imaging beamline at NSLS-II

The Full-field X-ray Imaging (FXI) beamline at the NSLS-II is designed for optimum performance of a transmission x-ray microscope (TXM). When complete, FXI will enable the TXM to obtain individual 2D projection images at 30 nm spatial resolution and up to 40 microns field of view (FOV) with exposure times of < 50 ms per image. A complete 3D nanotomography data set should take less than 1 minute. This will open opportunities for many real-time in-operando studies.

Microscopy Instrumentation and Nanopositioning at NSLS-II: Current Status and Future Directions

Synchrotron radiation newS, Vol. 31, No. 5, 2018 3 The development of ultra-brilliant synchrotron facilities and recent advances in the fabrication of efficient nano-focusing optics have stimulated rapid development and applications of the focused beams used to elucidate nanoscale phenomena in many areas of science and technology [1–5]. Various nano-focusing optics, including KirkpatrickBaez (KB) and elliptical mirrors, Fresnel zone plates (ZP), compound refractive and kinoform lenses, and multilayer Laue lenses (MLL), are routinely used to achieve nano-focusing. At present, KB mirrors, ZPs, and MLLs have demonstrated spatial resolution below 15 nm utilized in different scientific investigations [6–9]. When the focused beam size is reduced to below 100 nm, there is a need to develop a dedicated system tailored for a specific application, which satisfies stringent mechanical, vibrational, and thermal characteristics to successfully enable nanoscale imaging. Multiple degrees of motion, including their positioning accuracy, resonance frequencies, and amount of heat being dissipated, have to be thoroughly considered in order to efficiently perform nanofocusing experiments. Within the Imaging and Microscopy program at the National Synchrotron Light Source II (NSLS-II), a Department of Energy (DOE) Office of Science user facility located at Brookhaven National Laboratory, scanning and full-field imaging with direct spatial resolution down to 10 nm are available for the general user community. Most of the microscopes are developed in-house through a joint effort between the beamlines staff, the engineering group, and the nano-positioning team aimed to assist in design and construction of the cutting-edge microscopy instrumentation. Developed systems utilize state-of-the-art nano-positioning solutions, with some of them being adopted beyond the Imaging and Microscopy program at NSLS-II. The few examples presented here represent microscopy and nanopositioning systems developed at NSLS-II in recent years.

Burst mode pumping: A new mechanism of drinking in mosquitoes

Mosquitoes transport liquid foods into the body using two muscular pumps in the head. In normal drinking, these pumps reciprocate in a stereotyped pattern of oscillation, with a high frequency but small stroke volume. Do mosquitoes modulate their neuromotor programs for pumping to produce different drinking modes? More broadly, what are the mechanical consequences of a two-pump system in insects? To address these questions, we used synchrotron x-ray imaging and fluid mechanical modeling to investigate drinking performance in mosquitoes. X-ray imaging of the pumps during drinking revealed two modes of pumping: continuous reciprocation with multiple small strokes, and a newly discovered ‘burst mode’ involving a single, large-volume stroke. Results from modeling demonstrate that burst mode pumping creates a very large pressure drop and high volume flow rate, but requires a massive increase in power, suggesting that continuous pumping is more economical for drinking. Modeling also demonstrates that, from one mode of pumping to the other, the mechanical role of the individual pumps changes. These results suggest that the advantage of a two-pump system in insects lies in its flexibility, enabling the animal to pump efficiently or powerfully as demanded by environmental considerations.

One-minute nano-tomography using hard X-ray full-field transmission microscope

Full field transmission X-ray microscopy (TXM) is a powerful technique for non-destructive 3D imaging with nanometer-scale spatial resolution. However, to date, the typical acquisition time with the hard X-ray TXM at a synchrotron facility is >10 min for a 3D nano-tomography dataset with sub-50 nm spatial resolution. This is a significant limit on the types of 3D dynamics that can be investigated using this technique. Here, we present a demonstration of one-minute nano-tomography with sub-50 nm spatial resolution. This achievement is made possible with an in-house designed and commissioned TXM instrument at the Full-field X-ray Imaging beamline at the National Synchrotron Light Source-II at Brookhaven National Laboratory. This capability represents an order of magnitude decrease in the time required for studying sample dynamics with 10 s of nm spatial resolution.Full field transmission X-ray microscopy (TXM) is a powerful technique for non-destructive 3D imaging with nanometer-scale spatial resolution. However, to date, the typical acquisition time with the hard X-ray TXM at a synchrotron facility is >10 min for a 3D nano-tomography dataset with sub-50 nm spatial resolution. This is a significant limit on the types of 3D dynamics that can be investigated using this technique. Here, we present a demonstration of one-minute nano-tomography with sub-50 nm spatial resolution. This achievement is made possible with an in-house designed and commissioned TXM instrument at the Full-field X-ray Imaging beamline at the National Synchrotron Light Source-II at Brookhaven National Laboratory. This capability represents an order of magnitude decrease in the time required for studying sample dynamics with 10 s of nm spatial resolution.

Mouthpart conduit sizes of fluid-feeding insects determine the ability to feed from pores

Fluid-feeding insects, such as butterflies, moths and flies (20% of all animal species), are faced with the common selection pressure of having to remove and feed on trace amounts of fluids from porous surfaces. Insects able to acquire fluids that are confined to pores during drought conditions would have an adaptive advantage and increased fitness over other individuals. Here, we performed feeding trials using solutions with magnetic nanoparticles to show that butterflies and flies have mouthparts adapted to pull liquids from porous surfaces using capillary action as the governing principle. In addition, the ability to feed on the liquids collected from pores depends on a relationship between the diameter of the mouthpart conduits and substrate pore size diameter; insects with mouthpart conduit diameters larger than the pores cannot successfully feed, thus there is a limiting substrate pore size from which each species can acquire liquids for fluid uptake. Given that natural selection independently favoured mouthpart architectures that support these methods of fluid uptake (Diptera and Lepidoptera share a common ancestor 280 Ma that had chewing mouthparts), we suggest that the convergence of this mechanism advocates this as an optimal strategy for pulling trace amounts of fluids from porous surfaces.