You have a protocol that works. It has worked for years, run by hand, and the numbers come out clean every time. So you decide to automate it, and you assume the hard part is teaching the deck the steps: aspirate this, dispense there, move to the next well. That part is easy. The hard part is everything the protocol never wrote down, because the person who runs it does it without thinking.
A handheld protocol is a set of instructions wrapped around a skilled pair of hands, and most of the skill is invisible. The document says pipette 50 microliters of the reagent into each tube. It does not say that you pre-wet the tip twice first, that you hold the pipette at a slight angle, that you touch the tip to the side of the tube on the way out, or that you slow right down when the liquid is the viscous one. Your hand knows all of that. The robot knows none of it, and it never will unless you tell it in numbers.
Everything your hand does that the page never mentions
Before you can port a protocol you have to see the technique that the protocol takes for granted. Watch a skilled operator run the method by hand and you will notice a running stream of tiny corrections, none of which appear in the written steps. These are the moves that make manual pipetting reliable, and they are exactly the moves the robot will not make on its own.
- Pre-wetting: you aspirate and expel the liquid a couple of times before the real draw, so the tip interior is coated and the first delivered volume matches the ones after it.
- Angle and depth: you hold the pipette at an angle and keep the tip just below the surface, following the liquid down rather than plunging to the bottom or sipping air from above.
- Watching the meniscus: you actually look at the liquid climbing the tip, and you feel when a draw is short or a bubble came up, and you redo it before it becomes a bad well.
- Slowing down: for a viscous or a volatile or a foaming liquid you ease off automatically, giving the fluid time to follow the piston instead of tearing away from it.
- Touching off and tapping out: you touch the tip to the vessel wall to shed the hanging drop, and you tap or re-aspirate to clear a bubble you can see sitting in the tip.
- Feeling resistance: your fingers register when a tip is blocked, when a plunger is stiffer than usual, or when something is simply wrong, and you stop.
Every one of those is a control loop running in a human being. The robot has no such loop unless you build it, and it will happily deliver a short volume, a hanging drop, or a bubble-filled tip a thousand times in a row without ever noticing.
Perfectly consistent, perfectly literal
The trade you are making when you move from hand to deck is worth stating plainly, because it cuts both ways. A robot is far more consistent than any human: it will repeat the same motion at the same speed to the same depth for the entire run, without fatigue and without drift. That consistency is the whole reason to automate. The catch is that it is equally consistent about doing the wrong thing. It is perfectly literal. It does exactly what the parameters say, no more, and it brings none of the judgment that quietly rescued your manual runs.
This is why an instruction like pipette slowly and carefully cannot survive the move to a deck. Slowly is not a number and carefully is not an action. On the robot, slowly becomes an aspiration speed in microliters per second, and carefully unpacks into a specific list of settings you either specify or leave at a default that may be wrong for your liquid. The porting job is precisely this translation: turning verbs your hand understood into numbers the machine can execute.
The parameter equivalents of technique
Almost every manual move has an explicit counterpart in a liquid class, and the point of porting is to map one onto the other deliberately rather than by accident. Set them consciously, because if you do not, the default will set them for you.
- Pre-wet cycles: how many aspirate and expel cycles the tip performs before the real aspiration, the direct stand-in for the human habit of priming a tip.
- Aspiration and dispense speeds: the flow rates that encode slow down for the difficult liquid, tuned per liquid rather than left global.
- Tip immersion depth: how far the tip sits below the surface, the equivalent of following the meniscus instead of plunging to the bottom.
- Touch-off: whether and where the tip contacts the vessel wall after dispensing, standing in for the wall touch that sheds a hanging drop.
- Blowout: the extra push of air that clears the last of the liquid from the tip, which you must set rather than feel, and back off for a foaming reagent.
- Settling delays: deliberate pauses after aspirating or dispensing that let a viscous or slow liquid catch up before the tip moves, replacing the human beat of waiting.
- Mix cycles: programmed aspirate and dispense repeats in the well, the explicit form of the swirl or trituration you would have done by hand.
Written out like this, the tacit technique stops being feel and becomes a specification. That is uncomfortable at first, because it forces you to commit to values you were previously improvising, but it is also the only honest way to describe what a good run actually requires.
Start from a sensible class, then prove it
You do not derive these numbers from first principles. You start from a sensible baseline class, the one your platform ships for an aqueous liquid or a close analogue, and you adjust from there for the specific fluid in front of you. Then you validate, and you validate gravimetrically, because a balance does not care about your intentions. Weigh what the robot actually delivers across the volume range you use, convert by density, and read off the mean and the coefficient of variation. If a viscous reagent comes out light and variable, you slow the aspiration and add a settling delay and weigh again. The loop is empirical, and it ends when the numbers are inside your tolerance, not when the protocol looks plausible.
The vessels change too
Porting is rarely just a change of operator. By hand you were probably working in tubes, one at a time, at volumes chosen so a human could see and handle them. On the deck you are far more likely to be in a plate, many wells at once, sometimes at smaller volumes than you ever pipetted by hand. Well geometry, evaporation across a long run, and the immersion depth that made sense in a tube but not in a shallow well all shift underneath you. Do not assume the volumes and vessels transfer unchanged just because the chemistry did.
Porting surfaces the assumptions nobody wrote down
The most valuable thing about this whole exercise is not the automated protocol at the end. It is what porting forces into the open along the way. To hand the method to a machine you have to state every assumption the manual version left implicit, and you will find some of them were never really decided, only inherited. Somebody always pre-wet because their trainer did. The angle was habit, not a chosen value. Automating drags each of these into daylight and makes you either justify it or discard it, and your understanding of your own method comes out sharper than it went in.
The robot inherits your steps, not your care. Everything your hand did without being told is exactly what you now have to say out loud, in numbers.