# Mini linear actuator for syringe

_maxim_
TL;DR Summary
linear actuator syringe vial
Dear,

I would like to create a controlled system to inject 1-2 ml of liquid (a chemical reagent) into a solution contained in a glass flask.

The only request made is to use a reliable linear piston of minimum size, equal to or slightly larger than the injected volume (1 cm3) so that it can be easily fit into an already existing system, and with reduce power requirements (the system is battery operated).

The solution to be injected can be contained in a standard glass vial, or in a microsyringe (no needle is needed), or in another suitable container.

I've searched around a bit but I didn't find any linear actuator of the desired type, capable - for example - of moving the plunger of an insulin syringe by 1-2 cm.

The actuator must be capable to go back into the originale position in order to be a le to easily replace the vial (or the microsyringe, or whatelse).

Can you suggest any practical solutions?

Can you suggest any practical solutions?
Have you considered a peristaltic dosing pump?

_maxim_
Malapine
Solenoid fuel injector, if you can have a pressurized reservoir of more than 1-2 ml and just need to control the volume that is dispensed ?

_maxim_
_maxim_
Have you considered a peristaltic dosing pump?
Thank you Bal,

I've thought.. but all the mini peristaltic pumps I've found in the market are quite cumbersome to integrate or ratherly expansive.
I was thinking of a simple piston system to replicate the function of a simple syringe, but if you have a ready-made solution in mind and can share it, I'd be happy to consider it.

Last edited:
_maxim_
Solenoid fuel injector, if you can have a pressurized reservoir of more than 1-2 ml and just need to control the volume that is dispensed ?
Thank you Malapine,
the idea was to use not-pressurized and cheap container as vials or eppendorf-like, as in use in chemistry Labs.

Did you have some specific device in mind?

_maxim_
What about something like that, but even smaller?

Malapine
Thank you Malapine,
the idea was to use not-pressurized and cheap container as vials or eppendorf-like, as in use in chemistry Labs.

Did you have some specific device in mind?

A standard 1300cc/hour fuel injector from an auto parts store, if that would work.

_maxim_
A standard 1300cc/hour fuel injector from an auto parts store, if that would work.
Do you have a link to share?
I have the impression that are quite expansive devices...

Solenoid fuel injector, if you can have a pressurized reservoir of more than 1-2 ml and just need to control the volume that is dispensed ?
I would wonder what the internal materials might be, and how compatible they are with the chemistry. Cost is now quite low for injectors that indirectly inject gasoline into the airflow. I see on eBay, $50 will get you a set of six. That is now definitely worth investigation. I considered that solution for dosing growth units many years ago, but the prices then were much higher, so a peristaltic pump was used. 12V DC powered peristaltic dosing pumps, with a silicone tube, are now available on eBay for about$10 to $25. https://www.ebay.com.au/itm/174535247658 _maxim_ and Malapine Science Advisor Gold Member You might look into implantable insulin pumps that some diabetics use. Could be a few good ideas there. _maxim_ _maxim_ I would wonder what the internal materials might be, and how compatible they are with the chemistry. Cost is now quite low for injectors that indirectly inject gasoline into the airflow. I see on eBay,$50 will get you a set of six. That is now definitely worth investigation. I considered that solution for dosing growth units many years ago, but the prices then were much higher, so a peristaltic pump was used. 12V DC powered peristaltic dosing pumps, with a silicone tube, are now available on eBay for about $10 to$25.
https://www.ebay.com.au/itm/174535247658
Thanks Baluncore.

The problems I see in using a peristaltic pump are:
- the size (as I wrote, it must be quite small and comparable with the volume of injected reagent, 1-2 ml therefore about 1-2 cm3)
- the power supply requirements, being powered by small rechargeable batteries and not by cables for safety reasons, ideally within 5 Vdc (24 Vdc is too much)

Thanks for the link, I will check for something of similar (smaller and with low power consumption).

Great support 👍

_maxim_
Here: I had in mind a system similar to this but on a smaller scale, for example suitable for a 2ml commercial micro syringe without a needle:

The piston could be a part of the "cap" of the glass flask, while the syringe must be a disposable component, easily to replace.

_maxim_
You might look into implantable insulin pumps that some diabetics use. Could be a few good ideas there.
I did not find any spare parts in the market. Do you have a link to share?

Homework Helper
Gold Member
Could you give us a diagram with dimensions or a picture of the already existing system?
How frequent that operation must be?

_maxim_
_maxim_
Could you give us a diagram with dimensions or a picture of the already existing system?
How frequent that operation must be?
Thank you Lnewqban,
Just give to me a time to make a diagram of the system with dimensions and I will post it here.
The operation is once per time, maybe one or anyway a few per day. The syringe (or a similar container) must be easily replaced after the use with a new charged one, as a disposable part.

Lnewqban
Homework Helper
Gold Member
Thank you.
So, what needs to be exactly 1-2 ml of chemical reagent is the loading of each syringe (while in a vertical position).

_maxim_
I would like to create a controlled system to inject 1-2 ml of liquid (a chemical reagent) into a solution contained in a glass flask.
If it's not some thick, viscous liquid and on the level of a DIY project then just grab an old floppy disk drive head servo
It comes with a quite convenient interface/electronics too.

_maxim_
Gold Member
I did not find any spare parts in the market. Do you have a link to share?
A quick look found a site that sells used insulin pumps, USD $400 and up. New pumps seem to be$4000 and up and need a doctors prescription.
https://bimedis.com/search/search-items/infusion-pumps-insulin-infusion-pumps

Above, and many more, found with:

Another way to find details is to search the patent office:
https://www.uspto.gov/
Then enter Insulin Pump in the search field on the upper right of the page.

Cheers,
Tom

Lnewqban
_maxim_
Thank you.
So, what needs to be exactly 1-2 ml of chemical reagent is the loading of each syringe (while in a vertical position).
Yes, exactly!

_maxim_
If it's not some thick, viscous liquid and on the level of a DIY project then just grab an old floppy disk drive head servo
It comes with a quite convenient interface/electronics too.
It is mainly an aqueos solution... so the viscosity should be comparable with the water...

Nice idea! I guess it could be a pain to find a new floppy disk driver in the 2023

I have to see in my ceiling... but, exactly: which part did you have in mind? Head motor + movement screw? If I remember right, power requirements were quite high respect the low power consumption needed here with a battery...

_maxim_
A quick look found a site that sells used insulin pumps, USD $400 and up. New pumps seem to be$4000 and up and need a doctors prescription.
https://bimedis.com/search/search-items/infusion-pumps-insulin-infusion-pumps

Above, and many more, found with:

Another way to find details is to search the patent office:
https://www.uspto.gov/
Then enter Insulin Pump in the search field on the upper right of the page.

Cheers,
Tom
Thank you Tom,
but I think it is really too expensive for that purpose...

I have to see in my ceiling... but, exactly: which part did you have in mind? Head motor + movement screw?
Yes, but you need an even older, 5.25 sized one, which still has a decent stepper and two rails to aid the movement:

(source)
The smaller, 3.5 inch ones just won't have the power.

Honestly, on second thought I'm not sure about the old ones either. But ... well, it feelt like a good idea at that time

Mentor
I don't know if it's already been suggested, but can you just use a spring-loaded mechanism to drive the syringe piston? Is there a limit to how fast you are allowed to discharge the syringe? You could make something with a spring that you "cock" to the right distance, put in the syringe, and release the spring holding mechanism.

Lnewqban