Piranha Solution

Contents

1. Overview
2. Piranha single slide clean

1. Overview

Danger

Before working with piranha solution, read the full safety SOP, PPE requirements, and disposal instructions in Piranha Solution Safety SOP. Piranha is extremely hazardous—never let any organics (especially EtOH or acetone) come near it!

For bulk wafer cleaning in the MER cleanroom acid hood (2:1 H₂SO₄:H₂O₂):

• To clean one wafer: 800 mL of Sulfuric Acid with 400 mL of Hydrogen Peroxide.
• To clean a full batch of wafers: 1000 mL of Sulfuric Acid with 500 mL of Hydrogen Peroxide.

These large volumes of piranha are only mixed in the acid hood in the MER cleanroom, which provides the chemicals and materials needed.

2. Piranha single slide clean

This protocol (3:1 H₂SO₄:H₂O₂) is used for cleaning the patterned surfaces of flow cells after sufficient use (4 uses).

2.1 Materials Needed

• Pre-Cleaned slides to be washed
• Sulfuric Acid
• 30% Hydrogen Peroxide
• Glass Narrow Beaker or slide holder
• Larger beaker that can hold the narrow beaker
• Tweezers (Teflon is Best)

2.2 Protocol

1. In the acid hood, place the smaller beaker in the larger beaker.
2. Use a graduated cylinder to measure and add 30 mL of concentrated sulfuric acid to the small beaker first.
3. Use a separate graduated cylinder to measure 10 mL of 30% hydrogen peroxide and add it very slowly to the sulfuric acid in the small beaker (always add peroxide to acid, never acid to peroxide).
4. Let the piranha stand and react for 5 minutes.
5. Place a single slide into the small beaker on its end so that a small edge is still exposed. Let the slide clean for one minute.
6. After cleaning, wash the slide in water. Leave all slides in the water until piranha for all samples is done.
7. When piranha cleaning is done, transfer the used piranha to a bottle and set aside.
8. Transfer the slides from water to ethanol. After 15 minutes or longer dry the slide and put into the vacuum oven overnight.
9. At the end of the day, screw a cap loosely over the piranha.