3D-printed insoles measure sole pressure directly in the shoe

Date:
March 15, 2023
Source:
ETH Zurich
Summary:
Researchers are developing a 3D-printed insole with integrated
sensors that allows the pressure of the sole to be measured in the
shoe and thus during any activity. This helps athletes or patients
to determine performance and therapy progress.


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FULL STORY ========================================================================== Researchers at ETH Zurich, Empa and EPFL are developing a
3D-​printed insole with integrated sensors that allows the pressure
of the sole to be measured in the shoe and thus during any activity. This
helps athletes or patients to determine performance and therapy progress.


==========================================================================
In elite sports, fractions of a second sometimes make the difference
between victory and defeat. To optimize their performance, athletes use
custom- ​made insoles. But people with musculoskeletal pain also
turn to insoles to combat their discomfort.

Before specialists can accurately fit such insoles, they must first create
a pressure profile of the feet. To this end, athletes or patients have
to walk barefoot over pressure-​sensitive mats, where they leave
their individual footprints. Based on this pressure profile, orthopaedists
then create customised insoles by hand. The problem with this approach
is that optimisations and adjustments take time. Another disadvantage
is that the pressure-​sensitive mats allow measurements only in
a confined space, but not during workouts or outdoor activities.

Now an invention by a research team from ETH Zurich, Empa and EPFL could greatly improve things. The researchers used 3D printing to produce a customised insole with integrated pressure sensors that can measure the pressure on the sole of the foot directly in the shoe during various activities.

"You can tell from the pressure patterns detected whether someone is
walking, running, climbing stairs, or even carrying a heavy load on
their back -- in which case the pressure shifts more to the heel,"
explains co-​project leader Gilberto Siqueira, Senior Assistant
at Empa and at ETH Complex Materials Laboratory. This makes tedious mat
tests a thing of the past.

One device, multiple inks These insoles aren't just easy to use, they're
also easy to make. They are produced in just one step -- including the integrated sensors and conductors - - using a single 3D printer, called
an extruder.

For printing, the researchers use various inks developed specifically for
this application. As the basis for the insole, the materials scientists
use a mixture of silicone and cellulose nanoparticles.

Next, they print the conductors on this first layer using a conductive
ink containing silver. They then print the sensors on the conductors
in individual places using ink that contains carbon black. The sensors
aren't distributed at random: they are placed exactly where the foot
sole pressure is greatest. To protect the sensors and conductors, the researchers coat them with another layer of silicone.

An initial difficulty was to achieve good adhesion between the different material layers. The researchers resolved this by treating the surface
of the silicone layers with hot plasma.

As sensors for measuring normal and shear forces, they use piezo
components, which convert mechanical pressure into electrical signals. In addition, the researchers have built an interface into the sole for
reading out the generated data.

Running data soon to be read out wirelessly Tests showed the researchers
that the additively manufactured insole works well. "So with data
analysis, we can actually identify different activities based on which
sensors responded and how strong that response was," Siqueira says.

At the moment, Siqueira and his colleagues still need a cable connection
to read out the data; to this end, they have installed a contact on
the side of the insole. One of the next development steps, he says,
will be to create a wireless connection. "However, reading out the
data hasn't been the main focus of our work so far." In the future, 3D-​printed insoles with integrated sensors could be used by
athletes or in physiotherapy, for example to measure training or therapy progress. Based on such measurement data, training plans can then be
adjusted and permanent shoe insoles with different hard and soft zones
can be produced using 3D printing.

Although Siqueira believes there is strong market potential for their
product, especially in elite sports, his team hasn't yet taken any steps towards commercialisation.

Researchers from Empa, ETH Zurich and EPFL were involved in the
development of the insole. EPFL researcher Danick Briand coordinated
the project, and his group supplied the sensors, while the ETH and
Empa researchers developed the inks and the printing platform. Also
involved in the project were the Lausanne University Hospital (CHUV)
and orthopaedics company Numo.

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========================================================================== Story Source: Materials provided by ETH_Zurich. Original written by
Peter Ru"egg. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
*
The_insoles,_together_with_the_integrated_sensors_and_conductive_tracks,
are_produced_in_just_one_step_on_a_3D_printer.

========================================================================== Journal Reference:
1. Marco R. Binelli, Ryan van Dommelen, Yannick Nagel, Jaemin Kim,
Rubaiyet
I. Haque, Fergal B. Coulter, Gilberto Siqueira, Andre' R. Studart,
Danick Briand. Digital manufacturing of personalised footwear
with embedded sensors. Scientific Reports, 2023; 13 (1) DOI:
10.1038/s41598-023-29261-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230315132502.htm

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