Hi!
We are Max Neupert and Clemens Wegener
from the Center for Haptic Audio Interaction Research
Together with Marcel Ehrhardt
from the Thuringian Institute for Textile and Plastics Research
we are the authors of the paper
Piezoelectrical Strings as a Musical Interface.
The Thuringian Institute for Textile and Plastics Research
has developed a manufacturing process
to scale-up production for this flexible piezoelectric fiber
which can be used as a string
that has piezoelectric properties
and thus can sense vibrations or
audio from its surface and structure
without any additional pickups.
We were interested in exploring
the capabilities of this microphone
to excite digital resonators
so we were interested to use structure-borne sound
as a basis for sound generation,
this is why we looked into this specific technology.
Marcel Ehrhardt from the research institute
the TITK will show us the production process.
The piezoelectric polymer fiber is
produced as a coaxial fiber by means of
bi-component high temperature melt-spinning process.
The core consists of an electrically conductive
thermoplastic polyurethane
and a sheet of the piezoelectric polymer
polyvinylidene fluoride (PVDF).
The two materials are spun through a special nozzle
and cooled by a water bath.
the resulting thread is passed over an arrangement
of so-called godets
in order to adapt the diameter of
the fiber to the requirements,
but more importantly
to increase the degree of crystallization
of the PVDF.
the fiber is then passed through a electric field
in order to achieve the piezoelectricity
based on crystalline restructuring in the PVDF.
An outer electrode is placed on
the fiber using a circular braiding process.
The outer electrode surface dissipate
the charges generated by the piezo-effect.
The process can take place after polarization
and is a roll-to-roll-process.
Objective for this paper
was to highlight the strengths and weaknesses
and differences to other pickup technologies
like an electric guitar has or also like
an acoustic guitar picked-up with a
piezoelectric disk.
This new kind of piezoelectric fiber
doesn't come equipped with the typical ball-end
to have the tension of string
in the guitar or instrument.
also, the shielding of the piezoelectric fiber
is braided
while typical guitar strings are wound up
creating a different texture
a different kind of haptics:
when you use a bow
it behaves slightly different.
We also found that it can't withstand
the high tension that we need for most We also found that it can't withstand
the high tension that we need for most
instruments.
especially it would be hard to
bring it up to the tension needed for a piano string.
Also the soldering is
a bit more complicated because you can't heat it up
because the core will melt
so you have to use gluing technologies like
silver-particle acetone.
So, now let's demo
the piezoelectric string
we replaced one of these strings,
the G with our new sting
to compare this with the metal string:
As you can hear, it loses the tuning
very fast.
Interesting is, that
many small gestures
from the
string itself can be picked up
as opposed to the piezo-mic
which picks up these kind of
body sounds
In the sense of a prepared instrument
having a piezoelectric string
can be really interesting
to pick up this residual
parts of the sound.
Here we see the setup for our finger-violin
which consists of two rings
and the piezo-string in the middle.
Here we have a connector for the audio mixer
I put it on like this
put the fingers in the rings
apply some tension
and now I can pluck the string.
I can get all the fine
details of interaction on the string
it is a bit short the string
this is why the pitch is quite high.
To get more Q
for the string to resonate longer
we might need to have
more tension and a longer sting.
I think the
total pitch range is about one octave
we did not measure it precisely.
It is hard to
put more tension
to get a higher pitch
as the
pitch changes with the string tension in the square root
at some point you have to
put much more force to get a higher note.
The modified setup where we have
some signal processing
in the chain after the amplifier
which tracks the fundamental
pitch of our string and then
alters the signal
which is running through a little Karplus-Strong algorithm
so now if I pluck the string
the Karplus-Strong gets excited with the signal from our
piezo
and the pitch will be according to the
tension of the piezo string.
Now we can also bow
and it is a little bit easier to
keep the pitch
because the pitch is now quantized
to a full tone scale
but still: To keep the tension between the fingers
is a bit tricky.
We hope that this sparked your interest
and that piezoelectric fibers will become
something that is researched further
and maybe is used in
a NIME application for a new, cool
new instrument.
To facilitate this , we
provide, or we developed
a kind of a kit
together with the Thuringian Institue for
Textile and Plastics Research
This kit
includes a string
and a preamp
so you can connect it directly to phantom power
or - battery powered - for line-in.
So this will get you started
easily.
and hopefully there will be more interesting
research coming out in this field.
Alright, thanks for your attention!
Thanks for watching!