We’ve just released MicroDrop v2.0. You can get it here. We’ve been using this version internally for a few months now, and we think you’re going to love it! It has a lot of new features, including:

• droplet path routing
• improved video registration
• a new profile manager which enables switching between multiple MicroDrop profile directories (e.g., plugins, devices, etc.) on the same computer
• an improved system for installing plugin dependencies and auto-updating

We’ve created a YouTube playlist showing some of the new droplet routing features.

There’s still a bit of work to do updating the documentation, but instructions for installation and migration from v1.0 are complete.

Please note that there are some important caveats for upgrading from v1.0, but we have posted a method for installing both versions side-by-side to help with the transition.

If you run into any problems with installation, please post them to the dev list and we’ll try to resolve them as quickly as possible.

We just published an update for Microdrop (v1.0.18) that adds an exciting new feature: IPython notebook integration. This provides a quick and easy way to dive in and explore data logged during the course of your experiments. This could be useful for custom analysis of one-off experiments, or you can save notebook templates so that you can quickly apply a common set of post-processing steps to future experiments. If you need tighter integration with Microdrop, it’s straightforward to transition these notebooks into Microdrop plugins.

To access this feature, open the experiment log window from the menu item View/Experiment Logs and choose a log id from the drop down menu. There should be three new buttons : 1. Manage sessions..., 2. Open.. and 3. New... If you press the New... button, a file selection dialog will open in the Microdrop/notebooks folder. From here, you can choose a notebook template. We’ve provided two examples to get you started: “dump feedback results to csv.ipynb” and “Experiment log explorer.ipynb”.

If you choose one one of these templates, that file will be copied to your experiment log folder (i.e., “Microdrop/devices/device name/logs/log id/”) and an IPython notebook session will be launched in your default browser. To see an example of what one of these notebooks looks like, see this link. It demonstrates how you can dump feedback results to a *.csv file and plot drop velocity for a selection of steps in your protocol. After you’ve created a new notebook by copying a template (and optionally editing it), you can later open that notebook with the Open... button.

Note that each time you launch a new IPython notebook, it creates a new system process. These processes remain open until you exit from Microdrop, so if you create too many notebooks, it can cause a drain on your system due to high memory usage. The Manage sessions... button provides you with the ability to close down notebook sessions that you are no longer using by clicking on the Stop button next to the notebook you want to kill.

If you have questions/comments about this feature, please send them to the dev list.

We’ve recently noticed strange things happening when connecting/re-connecting to the control board during an experiment (e.g., drops randomly moving on the device, electrolysis, etc.), and while testing out the new hardware calibration routines (e.g., several fried op-amps in the feedback circuit). We hooked up an oscilloscope to the system and ran some tests to figure out what was going on.

When you initiate a connection to the DropBot (e.g., by launching the Microdrop application), the control board pulls a pin on the ATX power supply low to turn it on. This provides power to the daughter boards (e.g., the signal-generator board and high-voltage switching boards), which then power-up and initialize. During the power-up of the signal-generator board, transient voltages appear on the output pin within the first ~200 ms; if the amplifier is on during this time, it can output voltages in excess of +/- 200 V.

Oscilloscope screen showing high-voltage transients measured on the amplifier output during DropBot initialization. Each vertical line represents 100V.

Because the high-voltage switching boards are uninitialized at this point, high-voltage transients also appear on the outputs of all channels (though they are attenuated by roughly 50%).

Oscilloscope screen showing high-voltage transients measured on channel 0 during DropBot initialization. Each vertical line represents 100V.

These transients can cause damage to a connected DMF device (e.g., dielectric breakdown, electrolysis, etc.) if it is loaded with liquid. They can also damage the control board‘s impedance measurement (feedback) circuit if the test board is connected, since this board contains many large capacitors which provide a low-impedance path to the feedback circuit. In fact, this scenario caused us to fry several op-amps on our control board, which helped us to identify the problem.

To summarize, if the amplifier is on when you connect to the control board, high voltages may be applied to all channels in the system for a brief period (< 200 ms). To prevent damage, always make sure that the amplifier is off when you launch the Microdrop application. As an added layer of safety, you should avoid loading liquids onto your DMF device until after you have launched Microdrop. This way, even if the amplifier is on, it will not cause any damage to your DMF device or to the feedback circuit.

This problem can be addressed in future designs through hardware modifications to the control board, signal-generator board and or/the high-voltage switching boards.

Update 2015/03/18/: link to the portable v1.0rc0 instead of the earlier developer preview. This release candidate is considered stable for routine use; the only major change expected prior to v1.0 is the addition of a Windows installer.

We are getting set to release version 1.0 of the Micrdrop software as well as a couple of new hardware add-ons: (1) a test board and (2) an anti-aliasing filter shield. In combination, these improvements provide a simple method for users to quickly calibrate and benchmark their DropBot systems and to diagnose hardware problems. In addition, they significantly improve the accuracy of impedance-based measurements. We are in the process of upgrading our systems here to perform internal testing, but we thought we would share a preview of what’s in store.

This first set of screenshots shows a wizard for calibrating the reference load resistors. Once calibrated, this allows the DropBot to monitor the high-voltage output from the amplifier.

 
This next wizard is for calibrating the circuit responsible for measuring device impedance. This process makes use of the previously mentioned test board, which is essentially just a bank of known reference capacitors connected between one of the switching boards and the feedback cable (i.e., in place of a DMF device).

 
This final set of screenshots shows a test routine for checking the high-voltage switching boards. This can be useful for quickly identifying faulty solid-state relays.

 
One of the other changes with the upcoming software release makes it possible to run Microdrop as a portable application (e.g., from a folder or USB thumb drive) without installing the software. We still plan to provide an installer, but this will make it possible to run multiple versions of Microdrop on the same computer (e.g., one “stable” version and one “experimental” version).

If you are feeling brave and want to try out the release preview, download and double-click on the self-extracting zip file , then double-click on the Microdrop.bat file. Be warned that this version may not be compatible with your old protocols/plugins (we are working on upgrade tools, etc.). You will also need to download the new control board plugin (change log); click on the menu item File/Manage plugins, click the Download plugin... button, select dmf_control_board from the list and click OK. Once you restart Microdrop, it should give you the option to flash the upgraded firmware. Note that if you want to go back to the previous firmware version, you will need to re-flash the control board and recalibrate.

In the new year, we will post an official release (with a Windows installer) and provide some additional details on the new hardware and software features. If you have any comments or questions about the release, please direct them to the development email list.