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NEWS

December 2023 ESRFnews

S H U T T E R S T O C K/R P I L K O W S K I S H U T T E R S T O C K/A S H A R K Y U

ID16A exposes fruit-f ly leg sensors

A group led by the University of

Washington in Seattle, US, has made a

key insight into how neurons sense leg

movements in the common fruit fly.

To control our arms and legs

smoothly, our bodies rely on special

sensors called proprioceptors, which

help us know where our limbs are and

how they are moving, without relying

on visual cues. Proprioceptors come in

various types, and they work similarly

in both vertebrates and invertebrates.

Drosophila or fruit flies have one

known as the femoral chordotonal

organ (FeCO), which has a range of

sensory neurons. Some of these help

the fly know where its leg is, others tell

it which way its leg is moving, while

others sense vibrations.

To find out how each sensor detects

different aspects of movement, the

University of Washington scientists

used the ESRF’s ID16A beamline

to reconstruct the structure of the

FeCO by X-ray holographic nano-

tomography. They collaborated with

the ESRF’s Alexandra Pacureanu, who

is developing EBS-based techniques

to study neuronal systems as part of

a grant from the European Research

Council. “At ID16A, we have now

succeeded to push the limits of

resolving power and scalability to

support connectomics research,

and we know how to overcome the

challenges that this type of experiment

presents – namely, acquiring high-

resolution data of large and complex

3D samples, and generating a seamless

image volume,” she says.

Combining the nano-tomography

data with RNA sequencing, the

researchers discovered to their surprise

that the different sensors in the FeCO

are similar genetically, but connected

to the fly’s leg structure in different

ways mechanically. A computer

model showed how the mechanical

differences enable the sensors to detect

the angles of the leg joints. With help

from a technique known as calcium

imaging, the researchers confirmed

that a “map” in the fruit fly’s leg

keeps track of these joint angles. “We

discovered that the way these sensors

are built, and how they interact with

the leg’s structure, is more important

for their job than differences in

gene expression,” says University of

Washington biophysicist John Tuthill.

The findings could apply to other

sensory systems organised in a similar

way in different animals (Neuron DOI:

10.1016/j.neuron.2023.07.009).

ID31 explores composite

battery electrodes

An ID31 study of commercial-grade

composite battery anodes has revealed

insights into why high energy-density

lithium-ion batteries can fail prematurely,

which could help to improve the next

generation of batteries.

Predicting how a battery will age

requires a deep understanding of the

degradation mechanisms of each

single battery component and material.

This is more difficult when composite

electrodes such as graphite-silicon

are used, as the lithium ions are

stored within the constituent phases,

in this case the graphite and silicon

compound.

In a collaborative work within

the Battery Hub (see Insight, p10),

Sandrine Lyonnard at the French

Alternative Energies and Atomic Energy

Commission and colleagues used

wide- and small-angle X-ray scattering

(WAXS and SAXS) computed

tomography at the ID31 beamline to

monitor the lithiation of both graphite

and silicon-compounds in a composite

electrode, and to provide an in-plane

distribution of the phases in the

electrode – in operando mode and at

different depths.

They found that lithium-ion

batteries with thick electrodes,

which are industrially relevant and

have high capacity, exhibit two

types of heterogeneity: in-plane

heterogeneity, due to the uneven

mixing of graphite and silicon

compounds in the electrode, and

out-of-plane heterogeneity, due to

the gradual lithiation process that

occurs along the depth of the electrode

during operation One result is that a

composite graphitesilicon electrode

in a charged lithiated state can have a

silicon component that is more lithiated

close to the separator between the

anode and cathode where it can

potentially degrade faster Another

is charge redistribution at open

circuit voltage Adv Energy Mater

DOI 101002aenm202301874

These effects must be accounted for

to develop accurate predictions on

battery lifetime says Lyonnard

Like humans, the

fruit fly uses

proprioception to

know where its

limbs are, without

looking.

“At ID16A, we

have now

succeeded to

push the limits

of resolving

power and

scalability to

support

connectomics

research”