The document describes the design and construction of a pH-Rocker device needed to automate DNA sequencing experiments. Key factors that made manual stirring inconsistent are addressed. The design considers using readily available lab components to simulate circular motion without advanced electronics. Main components include a motor, motor arm, linkage, and stand to hold a 96-well plate and pH sensor for continuous, consistent stirring and pH measurements of reaction mixtures. Diagrams and pictures show the arrangement and construction of the pH-Rocker.

1. pH-Rocker
For
DNA-sequencing
experiments
By: Pranav Rathi
CHTM-UNM
1

2. Why pH-Rocker was needed?
• During DNA Sequencing reactions based on
quantification of pH measurements for analyzing
sequencing reactions, various factors made it difficult
to get consistent data. Few of them were changes in
pH in stationary reaction mixture and continuously
reaction mixture and speed of stirring (done
manually). To overcome this, pH rocker was
designed to help keep a steady speed for sensor and
also to keep a continuous stirring and get a
consistent data.
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3. Design of pH-Rocker
Things I Considered for design
• Something which can sort of simulate the circular motion by hand
• Do not require and advance electronics
• Do not require any specific tools or hardware not available in my lab 3

4. Components of pH-Rocker
RA90-thorlabs
post clamp TR12- thorlabs post
TR6- thorlabs post PK22G21-hennkwell
DC motor
CP02T-thorlabs
cage plate
PH37-SS
Hach company
pH sensor
CL6 -thorlabs
PH4-thorlabs clamp
post holder
96 well plate
Poweline variable MB6-thorlabs
DC-power supply breadboard
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5. Construction
Stand
Arrange all the parts as shown in the picture.
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6. Motor Arm
• This is the most important part of the
system; it simulates the arm
movement
• It is simple to make. I salvaged the
black disk from a radio and machined it
to fit the motor shaft
•I drilled 3 4/40 holes from the edge to
put the cage rod
Rubber • In end to hold the wire I Put 2 wire
cushion holder back to back, one of the holders
4/40 screws has a 4/40 hole to attach it to the rod.
Black disk
Linkage through ER1-thorlsba
wire holder 1’’ cage assembly rod
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7. Arrange the arm
• I made a 8/32 hole on the
cage plate and thread it to
hold the motor
• Arranged every thing as
shown in the picture
8/32 screw
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8. Mount the motor arm on the stand
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9. Some components
96 well plate
pH Sensor
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10. The pH- rocker is complete
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