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Design and Development of Electronic Pipettes (Part 2)
Naoto Izumo
R&D Division 5, A&D Company, Limited

In the previous Development Story, the results of market research into the micropipette market were discussed. However, as this occurred before application for intellectual property rights it was not possible to discuss the details of the technology involved in this new product. In this episode I will explain the aims of the development of the MPA Series of electronic pipettes and the functionality we devised to actually realize those aims.

It has been more than half a century since manual pipettes reached their present form. This could be interpreted as meaning manual pipettes that are presently sold in the market are completely perfected pieces of research equipment.

Modern day pipettes firstly move their pistons by the push of a button. They then work using the method of aspirating liquids due to the difference in air pressure created by the movement of the pistons. That is why they are called the air displacement type. These principles are highly praised as a means for measuring and moving liquids both safely and without contamination.

Presently in Japan, manual pipettes for aspirating and dispensing liquids account for 90% of the market, with the remaining 10% coming from electronic pipette sales. Among electronic pipettes, 90% of these are the multiple-channel type, which can have either 8 or 12 tips attached simultaneously. From this market background it can be inferred that the market share for single-channel electronic pipettes is a tiny 1% of total pipette sales volume.

Due to this sales history, we received many opinions from people in the industry along the lines of "Even if you introduce a brand new type of single-channel electronic pipette to the market, this by no means guarantees you'll be able to sell it!" Wherever we went we heard this same point of view. On the other hand, on occasion we also received comments such as "Even though I understand the convenience of electronic pipettes, sales are not presently increasing in the market and people are still waiting for an electronic device which meets all their needs."

While at first I was somewhat perplexed by these statements, after hearing them many times over I eventually gained a certain conviction in regards to electronic pipettes. This was that there are quite clear reasons why the market has not welcomed previous electronic pipettes and if these reasons can be removed from the equation, the majority of manual pipettes will be able to be replaced with electronic ones.

If the operation method for the presently predominant manual pipette is considered, the operation button is moved in the axial direction of the movement of the plunger while the pipette is held in the hand, so consequently it is the role of the thumb to operate the up and down movement of the button. When using a manual pipette, in order push down the operation button located at the head of the pipette with the thumb, the thumb must be held out perpendicular to the hand in a vertical direction, then bent horizontally at the joint. In order to properly operate the plunger, a force equivalent to 3 or 4 kg is required at the tip of the thumb.

There is a serious problem when the thumb is made to move like this: it has been designed to only be able to comfortably bend in the direction of the index finger. On the basis of this notion it is easy to come to the conclusion that the operating method of manual pipettes is a big concern from an ergonomic point of view. In fact, you could argue that even a short period of operation is inviting repetitive strain injuries in the thumbs.

With the aim of improving this area of concern with the operation method of the manual pipette, the new MPA Series was developed so that the pipette could be held with all fingers in a natural grasp, with the movement of the plunger able to be controlled with the ball of the index finger while maintaining that natural position.

Testing this new development, it has been verified that no strain occurs at all when aspirating and dispensing water over 3,000 times continuously over a 5 hour period. As a matter of fact, this test was conducted in order to confirm the longevity of the dedicated lithium ion battery, but when I heard that somebody had been made to perform this experiment for 5 hours alone I strongly admonished the person who commissioned the experiment. That is because I became concerned for the person having to actually perform this action continuously for 5 hours, imagining the effort that would be required with a manual pipette. However, when I asked the test participant the following day and heard there was absolutely no problem, I realized my anxiety was completely unwarranted.

When exchanging tips with the MPA, the release button is pushed with the thumb, but the thumb stays in a horizontal direction pushing downwards. The kilogram force required to operate this release button is relatively small, around 600 g, so absolutely no problems were found with this operation either. Incidentally, the kilogram force required to operate the aspirating and dispensing of the pipette with the ball of the index finger is approximately 300 g.

If strain is considered to come not just from the force required for operation, but from the impulse ? the force multiplied by the distance displaced (or duration of operation), the strain relating to operation of the piston for the MPA would be equivalent to less than 1/100 of current manual pipettes.

Electronic pipettes are said to be comparatively heavier than manual ones. In fact, the mechanical hardware that makes up the bulk of the weight of pipettes, such as the piston section and the screws that hold it in place, etc. are basically indistinguishable in weight between manual and electronic versions. But by adding the electronic components such as the motor, battery and electric substrate the weight does actually become about 1.5-2 times that of manual pipettes. However, you could say that most of the weight that people perceive is more governed by the center of gravity than the actual weight of the device. In other words, the most important point that should be considered for ease of holding the pipette is how far out the center of gravity of the device is from the axis of grip created when holding it.

With the MPA series the center of gravity of their weight (approximately 160 g) does not deviate from the axis of grip. Also, the display section was made more compact so that the center of gravity is lowered as much as possible. Thanks to these innovations, anybody holding the MPA for the first time will be pleasantly surprised by its lightness.

In addition to this sensation of lightness, importance has been placed upon the simple, yet specialized, function settings of basic, automatic aspirating and dispensing; multiple dispensing, which is the strong point of electronic pipettes; and a liquid mixing function. Further, it is now possible to select volume display in μL units and weight display in mg units, and the user can now easily perform calibration themselves in each mode. In particular, in mg display mode, by unifying measurement units when mixing liquids and powders, creating reagents or analysis samples, previously troublesome and easy to mess up concentration settings have now become much easier to perform.

The MPA Series is a single channel, adjustable volume electronic pipette. It includes four models of 10/20/200/1200, with the figures indicating the maximum possible volumes for aspirating and dispensing (μL). We hope the MPA Series of electronic pipettes will make a great contribution to a wide variety of fields, from medicine to foodstuffs, new materials or environmental measurement, being put to use creating samples for research, clinical trials or material analysis. We believe the MPA Series can lead to great improvements in productivity, increases in quality and advances in workplace health and safety, by greatly reducing occurrences of problems such as repetitive strain injuries.

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