## (1) Overview

### Modular functionality

The main highlight of the design of the open source multichannel pipette is its modularity and the ease to adjust the amount of liquid processed simultaneously. Each and every part of this assembly can be replaced for a nominal cost and without the need of any special training. Each syringe assembly acts a single independent unit, which can be replaced in the case of breakdown or contamination. At this point the device should be re-calibrated. Due to the use of independent syringe assembly the potential for sample contamination is essentially eliminated. In addition, the model can be modified with increased number of nozzles in multiple of 4 (i.e. 6) as well as the size of the syringe according to the needs of the researcher. This would still be an advantage although filling of the 96 well plate would need to be done length wise because of the spacing between the tips only allow every other well to be filled at a time.

### Reuse potential and adaptability

There has been a considerable quantity of research in the development of open source syringe pumps [61, 62, 63] based largely on 3D printing mechanical components and the use of the Arduino open source microcontoller [64] or Raspberry Pi single-board computer [61, 65]. These systems have been adapted to do multiple volumes [66] and even large volumes [67, 68] for extrusion-based additive manufacturing systems. In addition, multi-syringe systems have been built [61, 69] and open source syringe pumps have been demonstrated for high precision applications like occular drug delivery [70]. The development of the open source multichannel pipette system shown here can be coupled to the existing work on syringe pumps to drive the main piston. This would enable further automation and acceleration of science using a tool like Osman, an open source microsyringe autosampler [71] or the conversion of a 3D printer to a fluid handling robot [45]. Finally, open source syringe pumps have been augmented with feedback sensing and monitoring [72], which could be applied to the device here to for example automatically detect a clog in a single syringe during rapid pipetting. This would bring the scientific community one step closer to enabling scientists to fully digitally fabricate their open source labs [5, 73].

## (4) Build Details

### Build Details

#### Availability of material and method

The components of the open source multichannel pipette are shown in Figure 9 with part numbers that are defined in Table 2.

Figure 9

Open source multichannel pipette components that are detailed in Table 2.

Table 2

Components, quantity and their materials and sources. The full BOM and links are available https://osf.io/khupy/.

PART NO. PART NAME QUANTITY MATERIAL SOURCE

1a Enclosure (Body 1) 1 PLA Amazon

1b Enclosure (Body 2) 1 PLA Amazon

2 Main Plunger 1 PLA Amazon

3 Syringe Holder 1 PLA Amazon

4 1ml Syringe 4 Disposable plastic Allegro Medical

5 Compression Spring 4 Stainless steel McMaster-Carr

6 Female adapter 4 Disposable Plastic Cole-Parmer

7 Universal pipette tips 4 Disposable Plastic Amazon

8 Silicon medical tubing 3/16” OD 1 foot Silicon Freshwatersystems.com

9 M3x 35mm bolt 1 Stainless steel McMaster-Carr

10 M3 Nut 1 Stainless steel McMaster-Carr

There are 10 parts in total out of which the three main parts are designed in the FreeCAD [74] open source designing software. In this study they are 3D printed on an open source RepRap-based Lulzbot Taz 6 printer [75] after slicing the model in open source Lulzbot CURA in PLA. It should be pointed out, however, that any RepRap-class printer could be used to fabricate this device. As such printers can be purchased for under US$200 now it is possible that fabricating a single multichannel pipette could justify the purchase of a 3D printer. In addition, the costs of the device as shown could be reduced by fabricating it with other plastics including waste plastic using a distributed recycling and additive manufacturing (DRAM) model [77, 78, 79, 80, 81]. The remaining parts are widely available from the vendors like Amazon and McMaster-Carr in the U.S. and AliExpress or others depending on availability in the researchers’ home country. The BOM and the links for each part are provided in the BOM file in the repository (https://osf.io/khupy/). The total cost including 3D printing materials was under US$24 at the time of this writing. These costs would vary on the availability of commercial components and 3D printing filament. The costs, could for example be reduced to under US$20 by using recycled plastic filament manufactured by an open source recyclebot (waste plastic extruder) [82]. The validation of the pipette is carried out using a high precision analytical scale, but can be done using an open source scale for large volume syringes [83]. The design is assembled following Figure 10 and is relatively straight forward. Figure 10 The assembly process of the open source multichannel pipette: a) the syringes being assembled individually with springs, tips and tip holders and being inserted into the syringe holder, b) twisting motion needed to lock syringes into syringe holder, c) M3 nut and bolt are inserted into the enclosure, d) the main plunger in inserted into the enclosure, e) enclosure is tilted up so that the sliding surface that will hold the syringe holder is exposed, f) the main plunger is pushed up into the enclosure as far as possible and the syringe holder is slid into the enclosure by depressing the syringes against the springs, g) the syringe holder is pushed to the end of the slide in the enclosure, and h) the remaining enclosure component is slid into place. First as shown in Figure 10a the four syringes (part 4) have the compression springs (part 5) inserted between the plunger and the body of the syringe. Then female adapters (part 6), a short section of the silicon medical tubing (part 8) and the universal pipette tips (part 7) are placed on the end the syringe tip. This syringe assembly is inserted into the syringe holder (part 3). Figure 10a shows the syringes being assembled individually with springs, tips and tip holders and being inserted into the syringe holder, which calls for a twisting motion to lock them into place (Figure 10b). The M3 nut (part 10) and bolt (part 9) are inserted into the enclosure as shown in Figure 10c. The one challenging part is the screw nut has a seating slot that holds the nut tight once it is assembled. The nut must be inserted (part 10) into the slot such that it acts like a nut trap. Then, the user tightens the nut on the screw through the slot and pull it outwards to fix it in its seating space. Next, the main plunger (part 2) in inserted into the enclosure following Figure 10d. The device is now ready for the final assembly. The enclosure is tilted up so that the sliding surface that will hold the syringe holder is exposed (Figure 10e) and the main plunger is pushed up into the enclosure as far as possible (ensure the M3 bolt has not been tightened down). Then the syringe holder is slid into the enclosure by depressing the syringes against the springs (Figure 10f). The syringe holder should be pushed to the end of the slide in the enclosure (Figure 10g). Finally the remaining enclosure component is slid into place providing a completed open source multichannel pipette as shown in Figure 10h. Hardware documentation and files location: Archive for hardware documentation, modifiable design files, software and build files. Name: Open Science Framework Persistent identifier:https://osf.io/9tn6e/ Licence:GNU GPL v3 for documentation and CERN OHL v2 for the hardware Publisher:Ketan Mowade, Hrishikesh Kadam, Shubham Chinchane, Joshua Pearce Date published: 17/01/2021 ## (5) Discussion ### Discussion and Conclusions The design of the open source multichannel pipette is comfortable to use for an average sized hand and has a finger hold (as seen at the index finger in Figure 11) for compression of the syringes. Considering the multiple syringes it is subjectively easy to maneuver. Designing of this pipette is done in FreeCAD, which is an open-source free designing software and will allow other researchers to easily adapt it to their needs. Even though the multichannel pipette consists of several different parts, there is no use of binding material such as glue or screws to hold these parts together. The pipette is designed in such a way that it can be deconstructed easily so that the parts could be replaced in case of any damage. Even though the main body is 3D printed, there are certain parts of the pipette that cannot be 3D printed such as the syringes using fused filament fabrication at this time (although future work, particularly with open source SLA may make this feasible). The current design consists of just four 3D printed parts and can be mass produced in a distributed fashion in case of emergencies as has been observed with PPE during the COVID pandemic. This 3D printed multichannel pipette does satisfy ISO 8655 standards as seen in validation experiments and can be used in professional laboratories. It is also inexpensive enough, with the full BOM costing less than$24, that it could also enable students to have a ‘real’ research lab experience even in the undergraduate college and high-school levels. For example, it can be used to accelerate research by a factor of 4 to fill a 96 well plate as shown in Figure 11 as compared to a single channel pipette. This not only reduces research labor costs as detailed above, but can also have secondary benefits to the users. Björksten et al. have shown in a study of plunger operated pipettes that the prevalence of hand ailments among female laboratory assistants was found to be twice that among female state employees in general [84]. In their cohort a nested case-control study indicated that an increased risk of hand (OR = 5, 0) and shoulder (OR = 2, 4) ailments was associated with more than 300 hours of pipetting per year [84]. In the economic example above, using the 4 channel open source system provided here not only allows the research to while cutting labor costs but it also drops the user under the 300 hour recommended ceiling on pipetting time without compromising on quality. This is also a useful device to teach students about various fluid measuring devices, about 3D printing and how it can be used to fabricate precision products. Finally, the resolution of the pipette can still be improved as the resolution of the syringe graduation is 10 µL (e.g. the smallest markings on the used syringes were 10 µL per graduation marks).

Figure 11

The open source multichannel pipette in use filling a standard 96-well plate with fluid four wells at a time. Note that the multichannel pipette is operated at an approximately 45 degree angle when drawing and expelling fluid.

### Future Work

This design met the specifications for the intended project but could be improved. Due to the spacing of the syringes that was necessitated by their volume and the critical component users must pipette into every other well in a standard 96-well plate. This is adequate for some applications, but if pipetting with multiple colorless reagents in small volumes this could result in experimental error. This could be fixed in the future using smaller diameter commercially available syringes. For the target use scenarios, here larger 1mL syringes were used, however. Future work could also focus on removing the flexibility caused by the medical tubing in the tips by attaching the tips to the syringes directly with non-flexible couplings as well as enabling a fast removal of the tips. This may be possible by 3D printing couplings between different types of syringes and the common pipette tips. Future work can also focus on optimization and increasing the accuracy of the pipette. This design of pipette still uses 1CC syringes, which increases the size of the pipette. Use of smaller syringes is encouraged given that they can be used repeatedly for applications with smaller volumes needed. Future work is needed to investigate the impact of pipetting techniques using these multichannel pipettes [85] on precision and accuracy as well as new methods of calibration [86]. Future work is also needed to determine the devices function over long-term continuous use (e.g. to determine how many cycles is the calibration stable and is it dependent on fluid viscosity). In addition, future work can focus on increasing the resolution of the scale as the current resolution of the syringes is just 10 µL. Use of a custom scale on the syringes similar to [52] or using precision screw gauges instead of the volume adjusting screw (part 9 in Figure 9) may be viable methods to improve the performance of the device. In addition, development of a stepped plunger will allow users to pipette different volumes of fluid in each syringe depending on the step size such as has been done with the Biropette [87]. Various iterations of the design can be made like 8 channel pipette, 16 channel pipettes, etc. manufacturing with high precision 3D printer to get a better finish and better tolerances or the use of an open source high-temperature 3D printer [88] would allow for materials that can be sterilized with an autoclave or boiling. Lastly, as these devices are manually assembled with 3D printed parts, a future study could explore the differences in precision between devices that are printed on various types of printers and assembled by various individuals with different levels of fabrication experience to determine if the devices are still able to conform with ISO 8655.