The use of high power lasers and of piezo-based micromanipulators in nanoparticle-based photodynamic therapy

[Tiberius Brastaviceanu]

This discussion was initiated by Luciano, who is part of a group studying nanoparticle-based photodynamic therapy at the Brazilian Agricultural Research Corporation (Embrapa). 

We are interested in exploring the applications of Tibi's model about on photoionization modes, in conjunction with SENSORICA's suite of piezo-based micromanipulators.  

Luciano: 

Our group have synthesized a plethora of metal nanoparticles coated by biocompounds and some of them show photodynamic action towards specific target cells like cancer and pathogens and I really believe that your laser dose delivery systems could be used to enhance the effects of our nano-systems. In addition, I think that piezo manipulators like those that Antonio works on could, at least in vitro, be used to delivery nanoparticles and laser towards specific tissues or even cells if coupled to microscopes. There is a lot of potential applications of this kind of devices in biological fields.

[Tiberius Brastaviceanu]

Hi Luciano, 

I guess Antonio needs more precise technical requirements. Let me try to specify. 

Motion/displacement characteristics

Your application uses nanoparticles in photodynamic therapy. I suppose that these nanoparticles would be dispersed in space, and targets would be larger, the order of magnitude of biological cells. Here are some important parameters to consider. 

Range

Def: the maximal travel distance

Precision

Def: distance of every shot from average

Method: Make a certain step (lets say half of the range) many times, and measure the standard deviation of the distribution of measures. Change the step size and repeat the same.

Accuracy

Def: difference between the average and the real value (given by a "perfect" reference actuator)

Method: Make the same step (lets say half of the range) many times, and measure the mean/average and compare this average with the ideal model.

Resolution

Def: the smallest step an actuator can make

Method: Make consecutive small steps. See if there is a statistical difference between these steps. The resolution is the smallest step detectable. Perform the same procedure starting at a different position. Resolution range: is the resolution the same across the functioning range of the actuator? If not, can we have a profile?

Speed

What is the maximum speed required? 

Does speed need to be constant to a high degree?

Is speed control important?

Acceleration

What is the maximum acceleration required.

Is tight control on acceleration important?

Coordinated motion

If you want to use more than one axis, does your experiment require tight coordinated motion among the different axes? In other words, suppose you have 2 perpendicular axes. It is possible that you would want something to move in a circle. In that case, you need to have both axes coupled together in order to coordinate their motion to produce a resultant circular motion. How tight that coordination needs to be? 

Not so tight coordination can be done in software. Tighter coordination would require special, real time hardware. 

Load

What is the maximum weight the transducer has to move in space. 

Physical dimensions

If mounted on a microscope, what is the space it can occupy. Are the physical dimensions of our device OK? 

We would need a 3D model, or some parameters in order to understand is our current devices would fit, or the type of modifications would be needed.  

Based on these parameter we can chose one system among the prototypes that our network has produced. If we need something else, we can coordinate our efforts to design and prototype something different. 

NOTE: the amount of participation in new developments will depend on the incentives that are built around the project. 

From Antonio

Hi Luciano,

I'm quite busy these days working on a project, I would like to discuss better the application, but for me at this point, is more important to know better what exactly you expect from our manipulator. Can you send me some technical specification?

The device is not ready yet, but here is a very basic specification:

Linear Stage (using a internal piezo step motor)

1-axis linear stage dimentions: 58x58x22mm

Total translation travel range: 28-29mm

Min incremental step: 0.2 - 0.5 um   (not sure yet and dependent on the load)

Absolute minimal displacement: 1 - 10nm (bending mode, not a full step, not tested yet on a microscope) It's a future feature.

Max force: 4-5 N

Max load: still unknown

max speed: ~ 4-5 mm/s

Can be stacked to made the 3-axis as shown at the attached image.

We are developing our own driver, with specif features, but in the meantime a commercial driver can be bought at different configuration from same the piezo-motor factory we have bought the motors.