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The long-standing practice of data sharing in genomics can be traced to the Bermuda principles, which were formulated during the human genome project (Contreras, 2010). While the Bermuda principles focused on open sharing of DNA sequence data, they heralded the adoption of other open source standards in the genomics community. For example, unlike many other scientific disciplines, most genomics software is open source and this has been the case for a long time (Stajich and Lapp, 2006). The open principles of genomics have arguably greatly accelerated progress and facilitated discovery.

While open sourcing has become de rigueur in genomics dry labs, wet labs remain beholden to commercial instrument providers that rarely open source hardware or software, and impose draconian restrictions on instrument use and modification. With a view towards joining others who are working to change this state of affairs, we’ve posted a new preprint in which we describe an open source syringe pump and microscope system called poseidon:

A. Sina Booeshaghi, Eduardo da Veiga Beltrame, Dylan Bannon, Jase Gehring and Lior Pachter, Design principles for open source bioinstrumentation: the poseidon syringe pump system as an example, 2019.

The poseidon system consists of

  • A syringe pump that can operate at a wide range of flow rates. The bulk cost per pump is $37.91. A system of three pumps that can be used for droplet based single-cell RNA-seq experiments can be assembled for $174.87
  • A microscope system that can be used to evaluate the quality of emulsions produced using the syringe pumps. The cost is $211.69.
  • Open source software that can be used to operate four pumps simultaneously, either via a Raspberry Pi (that is part of the microscope system) or directly via a laptop/desktop.

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Together, these components can be used to build a Drop-seq rig for under $400, or they can be used piecemeal for a wide variety of tasks. Along with describing benchmarks of poseidon, the preprint presents design guidelines that we hope can accelerate both development and adoption of open source bioinstruments. These were developed while working on the project; some were borrowed from our experience with bioinformatics software, while others emerged as we worked out kinks during development. As is the case with software, open source is not,  in and of itself, enough to make an application usable.  We had to optimize many steps during the development of poseidon, and in the preprint we illustrate the design principles we converged on with specific examples from poseidon.

The complete hardware/software package consists of the following components:

We benchmarked the system thoroughly and it has similar performance to a commercial Harvard Apparatus syringe pump; see panel (a) below. The software driving the pumps can be used for infusion or withdrawl, and is easily customizable. In fact, the ability to easily program arbitrary schedules and flow rates without depending on vendors who frequently charge money and require firmware upgrades for basic tasks, was a major motivation for undertaking the project. The microscope is basic but usable for setting up emulsions. Shown in panel (b) below is a microfluidic droplet generation chip imaged with the microscope. Panel (c) shows that we have no trouble generating uniform emulsions with it.

droplet-results

Together, the system constitutes a Drop-seq rig (3 pumps + microscope) that can be built for under $400:

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We did not start the poseidon project from scratch. First of all, we were fortunate to have some experience with 3D printing. Shortly after I started setting up a wet lab, Shannon Hateley, a former student in the lab, encouraged me to buy a 3D printer to reduce costs for basic lab supplies. The original MakerGear M2 we purchased has served us well saving us enormous amounts of money just as Shannon predicted, and in fact we now have added a Prusa printer:

img_20190118_110506

The printer Shannon introduced to the lab came in handy when, some time later, after starting to perform Drop-seq in the lab, Jase Gehring became frustrated with the rigidity commercial syringe pumps he was using. With a 3D printer available in-house, he was able to print and assemble a published open source syringe pump design. What started as a hobby project became more serious when two students joined the lab: Sina Booeshaghi, a mechanical engineer, and  Eduardo Beltrame, an expert in 3D printing. We were also encouraged by the publication of a complete Drop-seq do-it-yourself design from the Satija lab. Starting with the microscope device from the Stephenson et al. paper, and the syringe pump from the Wijnen et al. paper, we worked our way through numerous hardware design optimizations and software prototypes. The photo below shows the published work we started with at the bottom, the final designs we ended up with at the top, and intermediate versions as we converged on design choices:

pump_psedotime_w_ref

In the course of design we realized that despite a lot of experience developing open source software in the lab, there were new lessons we were learning regarding open-source hardware development, and hardware-software integration. We ended up formulating six design principles that we explain in detail in the preprint via example of how they pertained to the poseidon design:

poseidon infographic

We are hopeful that these principles we adhered to will serve as useful guidelines for others interested in undertaking open source bioinstrumentation projects.

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