Instructions for Use "IFU" for 2PP printers

Our IFU for printing 2PP resins for two photon polymerization of nano & microstructures provide custom control of writing speed, resolution, precision and dimensional accuracy for the fabrication of transparent nano and microstructures.

3Dresyns calibration files and protocols are ideal for having maximum control of resolution, precision, dimensional accuracy, and printing speed. Depending on your goals, resolution, precision, dimensional accuracy, and printing speed can be balanced, or resolution, precision, and dimensional accuracy can be prioritised in detriment of printing speed, or vice versa. These generic guidelines can be used for calibrating our 2PP 3D resins in your specific 2PP printer and printing settings.

Features & Benefits of our 2PP 3Dresyns:

  • printable by most commercial two photon polymerization printers with wavelengths from 600 nm to 800 nm
  • supplied at different writing speeds: fast, intermediate, slow, and non reactive for custom control of writing speed and resolution 
    • tunable with the free sampled Fine Tuner 2PP FT8 Bio for custom adjustment of writing speed
    • tunable with the free sampled Fine Tuner 2PP LB3 Bio for maximum dimensionally accuracy and resolution with submicron feature sizes 
  • supplied in a relatively low and high viscosity version
    • choose a LV low viscosity version (<1000 mPas) for easy development or cleaning of uncured resin with conventional 2PP upright configurations
    • choose a HV high viscosity version (>2000 mPas) for upside down DiLL configurations
  • achievable feature sizes of 100-200 nm
  • designed for Dip-in two-photon lithography DTPL (also referred as Dip-in Laser Lithography DiLL) where the 2PP resin is immersed upside down in the microscope objective  
  • designed for conventional 2PP systems (also referred as Two Photon Lithography TPL) where the 2PP resin is positioned upright on the substrate  

Standard settings for printing 2PP 3D resins with 2PP printers:

3Dresyns 2PP “photoreactive” resins are non-chemically aggressive and have been designed to be used in DiLL technology, where the 2PP resins are placed between the microscope’s objective and the substrate. 3Dresyns 2PP can be used with wavelengths from 600 nm to 800 nm and relatively low, medium, and high intensity lasers, typically provided by pulsed Femtosecond Fibre Lasers with powers of 1- 100 mW, with different pulse duration (fs scale) and a repetition rate (MHz scale).

Follow our Instructions for Use IFU in detail for your specific 2PP printer specifications, such as laser wavelength, power, pulse duration, repetition rate, writing speed, etc.

Since each 3D resin requires certain energy dosage (mJoule) for curing, 2PP printers with relatively low or high light power (mW) need relatively longer or shorter exposure times for curing (energy dosage=power x exposure time). Consequently, the writing speed needs to be adjusted to the kinetics of each 2PP resin and 2PP printing specifications. Our free sampled Fine Tuner 2PP FT8 Bio and Fine Tuner 2PP LB3 Bio are ideal for custom increase of writing speed and achieving maximum dimensionally accuracy and resolution with submicron feature sizes (respectively).  

The 3Dresyns team has designed simple instructions for finding in just simple steps the best printing settings of our 2PP 3D resins in your specific 2PP printer specifications. Our calibration process is ideal for:

  • getting in just few easy steps the optimum writing speed of our 3Dresyns 2PP as supplied in your standard or chosen 2PP printer and printing settings, or
  • custom adjusting or fine tuning them with our Fine Tuner 2PP FT8 Bio and Fine Tuner 2PP LB3 Bio to custom increase writing speed, or dimensionally accuracy and resolution
    • It is recommended the use of Fine Tuner 2PP FT8 Bio in steps of 0.5-1% with high and low laser power 2PP printers respectively to increase gradually the writing speed. Avoid over dosage to avoid overcure of the resin beyond limits/specifications, resulting in potential loss of resolution of your prints
    • it is recommended the use of Fine Tuner 2PP LB3 Bio ULWA in increasing steps of 1% to reduce gradually overcure of the resin beyond specifications and obtain optimum resolution, precision, and dimensional accuracy of your 2PP prints in your specific 2PP printer settings

2PP Printing

Our 2PP 3Dresyns are photopolymer or light-curing resins which have been designed for 2PP printers working with a wide range of settings and specifications.

Calibration file 3Dtest1 “the coin” for tuning resolution, precision and dimensional accuracy

The above shown coin after reducing its size 1000 times can be used as calibration file for 2PP of flat structures, where micrometre units can be replaced by nanometre units (1000 nm =1 micron which symbol is µm). Resolution refers to the range of detail or minimum feature size which can be printed with detail. As shown on the surface of the coin the smallest feature size can be easily evaluated by reading the smallest concentric circle line on the surface of the printed coin, since each circle line has engraved its width and depth in decreasing order from 500 to 2 nanometres after reducing its size 1000 times.

On the other hand, precision refers to the capability to repeatedly print or "reproduce" the same dimensions of prints repeatedly with certain variation. Keep in mind that extremely precise prints are not necessarily dimensionally accurate unless the tree spatial xyz dimensions of prints coincide with the three spatial xyz dimensions of the designed stl files which define the theoretical dimensions of prints as defined in the stl files. 

Dimensional accuracy of 3D prints refers to how close the three spatial xyz dimensions of 3D prints are to the theoretical three spatial xyz dimensions of designed prints as defined in the stl file before printing.

The stl file of 3Dresyns flat coin as shown once reduced its size 1000 times will have 2 µm thickness (z axis) and 25 µm diameter (xy axis). The relative dimensional accuracy in the xyz axis can be easily measured by measuring the real diameter (xy axis) and thickness (z axis) of the horizontally positioned flat coin. For example, if the thickness of the printed coin is 2.1 µm.  The difference between the theoretical and real value is 0.1 µm (100 nanometres) and the % difference is 0.1/2x100=5% which indicates the relative dimensional accuracy in the z axis. The same principle applies to the xy dimensional accuracy. If for example the diameter of the printed coin is 25.25 µm.  The difference between the theoretical and real value is 0.25 µm (250 nanometres) and the % difference is 0.25/25x100=1% which indicates the relative dimensional accuracy in the xy axis.  

Our calibration stl files (including the coin shown above: are available for confirmation of printability, and for determining the xyz printing resolution, precision, and dimensional accuracy of the chosen printing settings in your existing printer, before printing your own designs. Our IFU provide you a full fingerprint of the achievable printing speed, resolution, precision, and dimensional accuracy of your chosen 2PP 3D resin in your 2PP printer.

The optimum printing settings for your chosen balance of printing speed, resolution, precision, and dimensional accuracy will be chosen by you, following our detailed IFU, with just some basic calibration steps.

How to choose the optimum laser power and writing speeds?

It is crucial that the following Curing Rate Table is filled up by you for getting the optimum laser powers at your chosen writing speed of the 2PP 3D resin in your 2PP printer specifications.  The power or intensity threshold and dynamic range can be easily determined by analysing the obtained data of the curing rate table.

How can you fill up the Curing Rate Table? By measuring the dimensions, height, thickness, resolution, and dimensional accuracy of 2PP resins cured at increasing laser powers, or if fixed at different writing speeds, or at increasing dosages of Fine Tuner 2PP FT8 Bio, and once curing is optimised followed by increasing dosages of Fine Tuner 2PP LB3 Bio ULWA for increasing resolution and dimensional accuracy.

Fill up the Curing Rate Table with the results of your measurements

It is recommended to represent increasing laser powers, which can be custom chosen to adapt them to different laser powers, writing speeds and overall 2PP resin and printer system settings and specifications.

Remember to evaluate the shape, measure the thickness of the printed coin, and write a comment about it in the same curing rate table.  All 2PP 3D resins pass from liquid to solid state, through a green state, in which the resin can be too tender or soft to resist gravity and keep its shape. Choose the optimum laser power to ensure that the 2PP resin has cured well enough to withstand its shape with detail. Typically, the optimum laser power is the maximum laser power before the shape starts to distort or loose resolution again due to over curing. 

Laser power (mW)*

 Curing Rate Table: Height, thickness, and accuracy of the cured flat coin** at different laser powers

 Values shown below are not real values: take YOUR OWN measurements yourself!

1

Example: 0 microns, uncured

5

Example: 0 microns, uncured

10

Example: shape distorted with poor detailed borders: rounded, poorly defined due to under curing: requires higher power, higher dosage of Fine Tuner 2PP FT8 Bio, or slower writing speed to cure properly

15

Example: shape distorted with poor detailed borders: rounded, poorly defined due to under curing: requires higher power, higher dosage of Fine Tuner 2PP FT8 Bio, or slower writing speed to cure properly

20

Example: shape still distorted with poor detailed borders: rounded, poorly defined due to under curing: requires higher power, higher dosage of Fine Tuner 2PP FT8 Bio, or slower writing speed to cure properly

25

Example: shape still a bit distorted with better detailed shape and borders: still rounded, still not well defined due to under curing: requires higher power, higher dosage of Fine Tuner 2PP FT8 Bio, or slower writing speed to cure properly

30

Example: shape similar to original stl shape with less detailed borders due to under curing  

35

Example: shape like original stl shape with higher resolution and more defined borders with similar accuracy to stl file. Further resolution and dimensional accuracy improvement can be obtained by adding Fine Tuner 2PP LB3 Bio ULWA in increasing steps of 1% to increase resolution and dimensional accuracy of the 2PP printed structure     

40

Example: shape similar to original stl shape with less detailed borders due to over curing

50

Example: some blistering caused by overcuring and too fast kinetics (exotherm)

75

Example: higher blistering caused by overcuring and too fast kinetics (exotherm)

100

Example: higher blistering caused by overcuring and too fast kinetics (exotherm)

*Note: with constant laser power, the curing rate table can represent increases of Fine Tuner 2PP FT8 Bio in steps of 0.5-1 %, or alternatively different writing speeds

**Note: the flat coin can be scaled down from its original size of 25 mm diameter and 2 mm thickness 100 or 1000 times to reduce its size down to 20 or 2 µm thickness (z axis) and 250 or 25 µm diameter (xy axis)

Print 3DTest1: the flat coin, in case you are interested in printing small parts and want to have a feeling of the achievable xy resolution:

  • Printing the coin flat with your chosen size (eg 1000 times smaller than the coin as supplied) is ideal for evaluating the printability and xy resolution
  • This first calibration test helps to identify the printability of the coin at your chosen size. This fast calibration file provides a proof of printability with the chosen settings, as well as an indication of xy resolution since each concentric circle has certain width and depth
  • The original coin once its size has been decreased 1000 times has its first concentric line with a width and depth of 500 nanometres (0.5 microns), the following ones have 400, 300, 200,150, 100, 80, 60, 40, 20, 10, 5, and 2 nanometres
  • This fast calibration tests gives an indication of the xy resolution, since the thinnest observed circle will determine the xy resolution of the resin with the chosen printing settings

Evaluation of the dimensional accuracy of the printed coin

  • Evaluate the xy resolution as shown before by reading the smallest width and depth of the printed concentric circles
  • Measure the thickness of the coin vs the theoretical 3Dtest1 thickness, which as supplied, after reducing its size 1000 times, has 2.0 microns, to quantify the z axis accuracy. This will permit you to calculate the % relative error in the z axis
  • If you are not fully satisfied with the quality, or detail, or accuracy of your prints it is necessary to fine tune the 3D resin even further with our Fine Tuners as mentioned before, and/or adjust your 2PP printing settings, e.g. by increasing or decreasing the laser power or writing speed. Depending on the origin of the print quality problem, different solutions are available.

Calibration file 3Dtest2: the “high aspect ratio obelisk” in case you are interested in printing high aspect ratio parts and want to know the maximum printable height as well as the achievable resolution, precision and dimensional accuracy.

Start printing 3DTest2: the “obelisk”

  • Directly print the obelisk with the best settings obtained for printing the coin
  • Increase or decrease the size of the obelisk in factors of 10 to preserve the scale of the concentric lines of the coin engraved of the faces of the obelisk
  • Use a similar height of the obelisk to the maximum height of your prints
    • Printing the obelisk with the biggest possible size is ideal for evaluating the printability of relatively big designs covering the maximum 2PP printable height
  • Depending on your results, use a more rigid or flexible, considering your required overall specifications
    • too flexible materials can bend over due to excessive flexibility

Cleaning and processing of prints:

The 2PP prints can be placed into the developer bath for 5-10 minutes and then dried with a gentle flow of air. After writing or printing the structures or prints development or rinsing of prints can be done with our Cleaning Fluids to remove the unexposed and uncured 2PP resin:

  • easy removal of uncured resin with conventional developers such isopropanol IPA and propylene glycol methyl ether acetate (PGMEA)
  • ideally use our biocompatible Cleaning Fluids to preserve transparency, prevent whitening and chemical attack of IPA and conventional alcohols

Full cleansing of prints

  • Depending on the final application, a deeper chemical post curing and cleansing can be done with our cleansing products, which are ideal for printing safe biocompatible systems
  • Explore our full range of cleaning fluids, detoxifiers, antimicrobial additives and purification kits for chemical "burn out" and elimination of any potential external unintended contaminants, polymerization by-products, impurities, leachables, and extractables
  • You are welcome to contact us and order more products and services by email at: info@3dresyns.com