Effect of sharp corners on electrode edges


#1

Hi

I am making a new design mask for our dropbot device (University of Helsinki, Sikanen’s group).

Our design have 6x15 electrode with wavy edges. To reach the second and the third column electrodes we need to pass two wires between the electrodes as shown in the attached figure. Since the edges are wavy, to minimize the distance between the electrode rows I need to have some sharp concentric corners. see the following figure

https://docs.google.com/file/d/0BzAEz6YpU7gZc2ZESDIxTVRDWjA/edit

Does someone in this forum know if sharp corners might cause some problem with the electric field?

Thanks for your help

Salvatore


#2

Hi Salvatore,

I should point out that whenever an electrode is not actuated, it is
actively pulled to ground, so it is possible to get shorts between
adjacent electrodes. Whether or not this happens will depend on your
voltage/frequency, dielectric, the gap between the electrodes,
moisture content, etc. We don't usually have a problem with gap sizes

25um unless we put devices in an incubator, in which case these types

of shorts become more common.

I expect those sharp corners will focus the electric field and make
shorts at those points more likely. My guess is that you'll have
better luck if you can round them out. That said, the only way to know
for sure is to try it out :wink:

-Ryan

···

On Tue, Sep 23, 2014 at 10:24 AM, Salvatore Cito <salvato...@gmail.com> wrote:

Hi

I am making a new design mask for our dropbot device (University of
Helsinki, Sikanen's group).

Our design have 6x15 electrode with wavy edges. To reach the second and the
third column electrodes we need to pass two wires between the electrodes as
shown in the attached figure. Since the edges are wavy, to minimize the
distance between the electrode rows I need to have some sharp concentric
corners. see the following figure

https://docs.google.com/file/d/0BzAEz6YpU7gZc2ZESDIxTVRDWjA/edit

Does someone in this forum know if sharp corners might cause some problem
with the electric field?

Thanks for your help

Salvatore

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#3

Hi Ryan,

thanks for the suggestion.

S.

···

On Tuesday, September 23, 2014 7:02:25 PM UTC+3, Ryan Fobel wrote:

Hi Salvatore,

I should point out that whenever an electrode is not actuated, it is

actively pulled to ground, so it is possible to get shorts between

adjacent electrodes. Whether or not this happens will depend on your

voltage/frequency, dielectric, the gap between the electrodes,

moisture content, etc. We don’t usually have a problem with gap sizes

25um unless we put devices in an incubator, in which case these types

of shorts become more common.

I expect those sharp corners will focus the electric field and make

shorts at those points more likely. My guess is that you’ll have

better luck if you can round them out. That said, the only way to know

for sure is to try it out :wink:

-Ryan

On Tue, Sep 23, 2014 at 10:24 AM, Salvatore Cito > > salva...@gmail.com wrote:

Hi

I am making a new design mask for our dropbot device (University of

Helsinki, Sikanen’s group).

Our design have 6x15 electrode with wavy edges. To reach the second and the

third column electrodes we need to pass two wires between the electrodes as

shown in the attached figure. Since the edges are wavy, to minimize the

distance between the electrode rows I need to have some sharp concentric

corners. see the following figure

https://docs.google.com/file/d/0BzAEz6YpU7gZc2ZESDIxTVRDWjA/edit

Does someone in this forum know if sharp corners might cause some problem

with the electric field?

Thanks for your help

Salvatore

You received this message because you are subscribed to the Google Groups

“dropbot-dev” group.

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#4

Dear Salvatore,

Sharp edges on an electrode have a tendency of inducing coronal discharge at high voltage (magnitudes higher than microfluidic actuation voltage). http://en.wikipedia.org/wiki/Corona_discharge You can expect a slightly higher actuation current, but this should be negligible until you reach the kilovolt range (I doubt any of us have the equipment to do that).

It should also be noted that the increased boundary area between your electrodes may induce a higher capacitance, but this should be negligible considering that the coplanar PCB traces used on the switching boards will most likely induce a higher capacitance than any minor increase in pad-to-pad area.

But I have no idea about what this might do to water droplets. You could theoretically be drawing a considerably larger amount of current or have a much larger power factor that your high voltage amplifier will have to make up for. Then again, you could also improve droplet velocity and power supply “demand.”

Do try it out.

···

On Wed, Sep 24, 2014 at 2:22 AM, Salvatore Cito salvato...@gmail.com wrote:

Hi Ryan,

thanks for the suggestion.

S.

On Tuesday, September 23, 2014 7:02:25 PM UTC+3, Ryan Fobel wrote:

Hi Salvatore,

I should point out that whenever an electrode is not actuated, it is

actively pulled to ground, so it is possible to get shorts between

adjacent electrodes. Whether or not this happens will depend on your

voltage/frequency, dielectric, the gap between the electrodes,

moisture content, etc. We don’t usually have a problem with gap sizes

25um unless we put devices in an incubator, in which case these types

of shorts become more common.

I expect those sharp corners will focus the electric field and make

shorts at those points more likely. My guess is that you’ll have

better luck if you can round them out. That said, the only way to know

for sure is to try it out :wink:

-Ryan

On Tue, Sep 23, 2014 at 10:24 AM, Salvatore Cito

salva...@gmail.com wrote:

Hi

I am making a new design mask for our dropbot device (University of

Helsinki, Sikanen’s group).

Our design have 6x15 electrode with wavy edges. To reach the second and the

third column electrodes we need to pass two wires between the electrodes as

shown in the attached figure. Since the edges are wavy, to minimize the

distance between the electrode rows I need to have some sharp concentric

corners. see the following figure

https://docs.google.com/file/d/0BzAEz6YpU7gZc2ZESDIxTVRDWjA/edit

Does someone in this forum know if sharp corners might cause some problem

with the electric field?

Thanks for your help

Salvatore

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Sincerely,

Brandon Lu
UCR PCI-E Usergroup