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Drop formation sequence for drop-on-demand ink-jet
Drop on demand is illustrated using a 55 micron orifice. The illumination uses a short pulse synchronized with the drop generation. By changing the delay between the illumination pulse and the actuating signal that generates the drop, the drops are
captured at various locations along their flight path. This short movie is obtained by capturing images at various locations along the drop trajectory.
Drop generation for ink-jet at higher frequencies
This is illustration of a drop on demand ink-jet dispenser that generates drops at a higher frequency. The higher frequency correspond to a shorter time between two consecutive drops which leads to a smaller distance. Thus, more drops are visible in the captured image.
Merging and mixing of drops in flight
Each of the two dispensers create on-demand 50 micrometer drops at a frequency of 480Hz. The synchronous illumination allows tracking of the droplets along their flight path. The timing and orientation are set such that the droplets merge into a single drop. Some oscillation can be observed after merging.
This approach was taken to study the dynamics of a reaction. In the image to the right, one of the solutions becomes fluorescent when the solution pH is high. The second solution has a high pH. For this image, the illumination is continuous at a wavelength that excites the fluorescent dye. The fluorescence is observed after the droplets merge and becomes more intense as the two solutions mix. There are more intense regions of illumination that would correspond to the presence of the high pH solution inside the merged drop.
Dispensing into test tubes using a valve jet
Dispensing larger volumes in a single event can be achieved using an ink-jet valve. The released fluid has the appearance of a long slug. This movie shows the dispensing of a biomedical reagent into test vials.
Dispensing of cells
This movie is an example of dispensing liver cells with an average size around 10um. As the fluid is ejected in the forms of drops, cells can be observed flowing down and exiting the orifice.
For uniform coverage (discrete or overlapping spots) it is often more efficient to move the substrate at constant speed while drops are generated continuously. For drop spacing is determined by the substrate speed and the drop generation frequency. MicroFab's control program allows both uniform spacing (drops generated at constant frequency) or non-uniform spacing (drops generated based on position - trigger from the encoder).
In this example the substrate speed was slowed down significantly to permit the visualization of the individual drops.
Dispensing larger volume by multidrop accretion
Larger volumes are ink-jet deposited using multiple drops. The substrate is non-wetting and produces an almost hemispherical fluid accumulation. The individual droplets are observed above the accumulated fluid.
Dispensing at multiple locations on a test plate
This is an example of dispensing onto a test plate in a move-stop-dispense mode. Larger volumes are generated by depositing multiple drops at one location.
Dispensing water-based solution onto a PTFE membrane
A water-based solution is dispensed onto a PTFE membrane as several 3 by 3 arrays with multiple drops at each location. The high contact angle of the solution on the membrane makes the liquid dispensed at each location ball-up. Individual droplets can be observed above the increasing volume dispensed at each dispensing location.
Printing onto a cardiac stent with drug reservoirs on the struts
This movie illustrates printing into the individual wells of a cardiac stent. The wells fabricated in the struts of the stent act as reservoirs to control the release of the drug. Ink-jet dispensing fulfills the requirement of depositing the drug compound only inside the wells. A second dispenser can be used to deposit polymer solutions between layers of drugs or to cap the well. The layers and cap can control the release kinetics of one or multiple drugs.
Printing onto a "simulated" cardiac stent with drug reservoirs on the struts
The mock-up stents were coated by moving the stent in a coordinated fashion under the ink-jet microdispenser. Printing was done "on-the-fly" by moving the stent continuously (rotation and axial movement) and generating drops based on the desired spot to spot spacing.
Axial view of the printing
The video shows an axial view (camera along the stent axis) of the stent coating process. The end of the glass nozzle that is part of the piezoelectric microdispenser is observed on the center of the screen. The landing of the fluid droplets can be observed on the strut that is running from lower left to upper right and is in focus. The fluid appears as a continuous surface that moves as the strut moves under the microdispenser. At the end of the video (when the end of the stent is placed under the device) the fluid evaporating from the strut can be observed.
Lateral view of the printing
The video shows a side view (camera perpendicular to the stent axis) of the stent coating process with the microdispenser glass tube being vertical on the center of the stage. The stent is positioned horizontally under the dispenser. In the video, this motion is done along one strut in one direction and along another strut in the opposite direction. When the stent moves towards the right the fluid deposited onto the struts can be barely seen as an appearing (deposition) and disappearing (evaporation) “bump” to the right of the ejected droplets. When the stent moves towards the left the “bump” appears to the left of the droplets.
This movie is an illustration of the vapor generation using ink-jet dispensing as applied to MicroFab's VaporJet™ system. An RTD is used as heater and sensor by rapidly switching from a power to a reading/measurement cycle. This implementation allows to very fast heating rates due to the small thermal mass.
In this movie the heater is maintained at a constant temperature while 40 micron drops of isopropyl alcohol are generated at 4600Hz. The heater is set at 100 degrees Celsius. As the droplets land on the heater they evaporate and are taken to the outlet by the carrier flow. There is a balance between the evaporation and droplet generation rate.
The outlet concentration can be changed by adjusting the drop generation frequency and/or the carrier flow rate. The vapor of interest could be the one form the fluid or any other solids dissolved in it. For fluids/solutions with higher boiling point, the temperature of the heater can be increased to prevent accumulation.
Dye assisted laser ablation
The dye minimizes the reflection of the incident laser beam by the tooth enamel. In the movie, a drop is deposited for the alignment of the laser fiber. After that, a sequence consisting in deposition of a drop of dye followed by a short laser pulse is repeated at 10 Hz. The energy absorbed by the dye results in the removal of the tooth material. The dimension of the formed crater is slightly under 1mm in diameter.
Jetlab® software demo
This movie illustrates the main steps in setting up drop generation and printing a simple pattern using the Jetlab® software.
Jetlab® drop analysis demo
This movie illustrates the use of Jetlab® software to determine the drop parameters (diameter, velocity and trajectory angle).