Types of Western Blotting Equipment (Cells & Power Supplies)

This section provides an overview of the various blotting equipment available from Bio-Rad for different transfer methods, such as tank blotting, semi-dry blotting, and microfiltration or dot-blotting. It provides specifications for different transfer cells, and also describes the power supplies available for these systems.

Related Topics: Membranes and Blotting Papers, Transfer Buffers, Transfer Conditions, and Detection and Imaging after protein blotting.

Page Contents
Tank Blotting Cells

The tank transfer systems offered by Bio-Rad are described below, and their specifications are summarized in the table below. Selection of the appropriate system is largely dictated by the gel format used for separation and the desired throughput.

Tank transfer systems contain the following elements:

  • Buffer tank and lid — the buffer tank and lid combine to fully enclose the inner chamber during electrophoresis. On the inside, the tank has slots for placement of the electrode cards, gel holder cassettes, and cooling element. Ports on the lid allow connection points for the electrodes and are energized using an external power supply
  • Gel holder cassette — the gel and membrane sandwich is held together between two foam pad and filter paper sheets, and placed into the tank within a gel holder cassette. Cassettes are made of non-conductive material and designed to permit unimpeded flow of current and buffer through the gel and membrane sandwich
  • Electrodes — tank transfer systems use either plate or wire electrode cards. Plate electrodes offer greater field strength than wire electrodes but wire electrodes may be more economical and generate less heat
  • Cooling mechanism — cooling systems consist of an ice block, a sealed ice unit, or a cooling coil that is coupled to an external cooling mechanism. These cooling systems prevent temperature fluctuations and overheating during high-intensity, extended, or native protein transfers

Mini Trans-Blot® Cell and Criterion™ Blotter
The Mini Trans-Blot cell and the Criterion Blotter accommodate mini- and midi-format gels, respectively. The Mini Trans-Blot cell can transfer up to two mini gels (10 x 7.5 cm) in an hour and is available either as a complete apparatus or as a module that uses the buffer tank and lid of the Mini-PROTEAN® Tetra cell for operation. A self-contained Bio-Ice™ cooling unit absorbs the heat generated during transfer.

Mini Trans-Blot cell

The Criterion Blotter can transfer up to two Criterion gels (15 x 9.4 cm) or four mini gels simultaneously in 30–60 min. Temperature regulation during transfer can be achieved through the use of a sealed ice-block or optimal cooling coil.

Criterion blotter

Trans-Blot® Cell
The Trans-Blot cell offers a choice of plate or wire electrodes and variable placement of the electrodes for either standard or high-intensity blotting options. The Trans-Blot cell accommodates three gel holder cassettes, each with a 16 x 20 cm blotting area. This system is best for transfer of large-format gels or multiple mini- or midi-format gels. Standard field transfers are performed with the electrodes placed 8 cm apart; with this arrangement, all three of the gel holder cassettes can be used simultaneously. High-intensity transfers can be performed with the electrodes placed 4 cm apart, with a single gel holder cassette between them. Temperature regulation can be achieved using the super cooling coil (included) and a refrigerated water recirculator (purchased separately).

Trans-Blot cell

Trans-Blot® Plus Cell
With a 28 x 26.5 cm blotting area, the Trans-Blot Plus cell has the capacity to transfer three large-format gels or multiple smaller format gels simultaneously in as little as 15–30 min. Adjustable plate electrodes provide a strong and uniform electrical field — up to three gel cassettes can be placed in the tank with the minimum electrode distance between them, increasing the field strength and transfer efficiency. A cooling coil coupled to a refrigerated water recirculator provides temperature regulation.

Trans-Blot Plus cell

Specifications for Bio-Rad's tank blotting cells.

  Mini Trans-Blot® Criterion™ Blotter Trans-Blot® Trans-Blot® Plus
Blotting area
(W x L)
10 x 7.5 cm 15 x 9.4 cm 16 x 20 cm 26.5 x 28 cm
Gel capacity 2 Mini-PROTEAN® gels 4 Mini-PROTEAN or 2 Criterion™ gels 3 PROTEAN® II xi, 6 Criterion, or 12 Mini-PROTEAN gels Three 26.5 x 28 cm gels or 12 Criterion gels
Number of gel holders 2 2 3 3
Buffer requirement 1.2 L 1.3 L 3–4 L 10–12 L
Electrode distance 4 cm 4.3 cm 2 positions: 4 and 8 cm 3 positions: 4, 7, and 10 cm
Electrode materials Platinum wire Platinum-coated titanium anode with stainless-steel cathode plates or platinum wire Platinum-coated titanium anode with stainless-steel cathode plates or platinum wire Platinum-coated titanium anode and stainless-steel cathode plates
Transfer time
Wire electrodes Standard:
16 hr
1 hr
Standard: 60 min to overnight Standard: 5 hr Overnight: 16 hr High-intensity: 30 min–4 hr  
Plate electrodes   Standard: 30 min to overnight Standard: 1–5 hr Overnight: 16 hr High-intensity: 15 min–1 hr Standard: 16 hr High-intensity: 30 min–1 hr
Cooling Blue cooling unit Sealed ice block or optional Criterion blotter cooling unit Super cooling coil Super cooling coil
Overall dimensions (W x L x H) 12 x 16 x 18 cm 21.8 x 11.8 x 15 cm 18 x 9.5 x 24 cm 30 x 17.3 x 39.4 cm
Semi-Dry Blotting Systems

Semi-dry transfer generally allows faster transfer and is more economical than tank blotting as it uses a smaller volume of buffer. Semi-dry systems do not offer external cooling.

Specifications for Bio-Rad's semi-dry blotting cells.

  Trans-Blot® SD Trans-Blot® Turbo™
Blotting area (W x L) 24 x 16 cm 15 x 11 cm
Gel capacity 2 PROTEAN II gel sandwiches, stacked and seperated by dialysis membrane; 4 Mini-PROTEAN gels; 3 Criterion gels 2 midi gels (13.5 x 8.5 cm), 4 mini gels (7 x 8.5 cm) or similar
Transfer time ˜30 min 3–10 min
Buffer requirement 200 ml N/A
Electrode dimensions 25 x 18 cm 16 x 12 cm
Electrode distance Determined by thickness of the gel and membrane sandwich and filter paper stack ˜8 mm depending on gel thickness<
Electrode materials Platinum-coated titanium anode and stainless-steel cathode Platinum-coated titanium anode and stainless-steel cathode
Cooling N/A N/A
Overall dimensions (W x L x H) 37 x 24 x 11 cm 26 x 21 x 20 cm

Trans-Blot® SD Semi-Dry Cell
The Trans-Blot SD semi-dry cell performs electrophoretic transfers in 15-60 min. Plate electrodes and a single-step locking system make assembly easy and ensure uniform contact across the entire electrode surface.

Trans-Blot SD cell

Trans-Blot® Turbo™ Transfer System
The Trans-Blot Turbo system perform semi-dry transfers in as little as 3 min. Turbo transfers are achieved using prepackaged transfer packs containing a nitrocellulose or PVDF (polyvinylidene difluoride) membrane and filter paper stacks pre-wetted with a proprietary buffer. The system can also perform traditional semi-dry transfers with standard filter papers, membrane, and Towbin buffer. The base unit contains an integrated power supply that drives two independent transfer cassettes, allowing maximum throughput of four mini-format or two midi-format gels.

Trans-Blot Turbo System

Microfiltration Apparatus

The Bio-Dot® and Bio-Dot® SF microfiltration units provide reproducible methods for binding proteins or nucleic acids in solution onto membranes. Once samples are loaded into the wells of the templates, proteins are trapped on the membrane by either vacuum or gravity flow filtration. All subsequent incubation, wash, and detection steps may be performed without removing the membrane from the unit.

The 96-well Bio-Dot apparatus performs traditional dot-blot comparisons, and the 48-well Bio-Dot SF apparatus focuses the applied samples into thin lines instead of circles, which makes it easier to use a densitometer for quantitation. Both sample templates are interchangeable and use the same microfiltration manifold. Both apparatuses are available as a complete unit containing the microfiltration manifold and sample template, or as a modular template without the manifold base.

The Bio-Dot and Bio-Dot SF units can be easily sterilized by autoclaving or by washing in alcohol or sodium hydroxide. The units feature a unique, patented sealing gasket that eliminates lateral leakage and possible cross-contamination among wells. Additionally, sample templates are spaced similarly to microplates, allowing samples to be applied with a standard or multi-channel pipet.

Microfiltration apparatus

Multiple sample comparisons are simplified with the Bio-Dot and Bio-Dot SF microfiltration units

Multiple sample comparisons are simplified with the Bio-Dot and Bio-Dot SF microfiltration units. A and B, antigen (human transferrin) applied to nitrocellulose in each row of the Bio-Dot apparatus. 1, 100 ng; 2, 50 ng; 3, 25 ng; 4, 10 ng; 5, 5 ng; 6, 2.5 ng; 7, 1 ng; 8, 0.5 ng; 9, 0.25 ng; 10, 1% BSA in TBS. C and D, antigen applied to each row of the Bio-Dot SF apparatus. 1, 100 ng; 2, 50 ng; 3, 10 ng; 4, 5 ng; 5, 1 ng; 6, 0.1 ng. The membranes were incubated with rabbit anti-human transferrin. In A and C, Bio-Rad's goat anti-rabbit gold conjugate and gold enhancement kit were used to visualize the antigen. In B and D, Bio-Rad's goat anti-rabbit AP conjugate and the color development reagents BCIP and NBT were used to visualize the antigen.

Specifications for Bio-Rad's Bio-Dot microfiltration units.

  Bio-Dot Bio-Dot SF
Sample format 96-well, 8 x 12 format 48-slot, 6 x 8 format
Well size 3 mm diameter 7 x 0.75 mm
Sample volume 50–600 µl 50–500 µl
Membrane size (W x L) 12 x 9 cm 12 x 9 cm
Autoclavability Yes Yes
Power Supplies for Electrophoretic Transfers

Electrophoretic transfer cells require high currents that not all power supplies are equipped to deliver. The two Bio-Rad power supplies below are designed to accommodate the needs of electrophoretic transfer systems.

PowerPac™ HC Power Supply
The PowerPac HC (high current) power supply is capable of driving all transfer cells to their maximum performance. The PowerPac HC power supply offers high power output along with the flexibility of choosing transfer under constant voltage, constant current, or constant power settings. The PowerPac HC power supply also offers highly regulated voltage settings, fine adjustment of current limits, and a convenient pause function. Safety features include overload/short circuit detection, automatic crossover, arc and ground leak detection, programmable multi-step methods, and a programmable timer.

PowerPac™ Universal Power Supply
The PowerPac Universal power supply is designed to drive all of the most common electrophoretic applications, with the exception of high-voltage applications such as isoelectric focusing and DNA sequencing. Like the PowerPac HC power supply, the PowerPac Universal power supply provides the choice of transfer under constant voltage, constant current or constant power settings with all of the other features listed above. In addition, the PowerPac Universal stores up to nine methods, each with up to nine steps, and is equipped to enable wireless transfer of run data and protocols for instrument validation for regulatory purposes (for example, installation qualification and operational qualification, or IQ/OQ).

PowerPac Power Supplies

Specifications for PowerPac™ HC and PowerPac™ Universal power supplies.

  PowerPac HC PowerPac Universal
Voltage 5–250 V 5–500 V
Current 0.01–3.0 A 0.01–2.5 A
Power 1–300 W 1–500 W

For more information on power/running conditions, see Performing Electrophoresis section.


Trans-Blot® Turbo™ System vs. Traditional Blotting Techniques
This video demonstrates how the Trans-Blot Turbo system measures up against traditional blotting techniques both interm of equipement and supplies needed and speed.
Trans-Blot Turbo System Instructional Video
Trans-Blot® Turbo™ System Instructional Video
This instructional video highlights the main features of the Trans-Blot Turbo system as well as the easy assembly and transfer process. Helpful tips are provided along the way to ensure customer success.
Trans-Blot SD Semi-Dry Electrophoretic Transfer Cell
Trans-Blot® SD Semi-Dry Electrophoretic Transfer Cell: Application, Assembly, and Troubleshooting
This video demonstrates how the Trans-Blot Turbo system measures up against traditional blotting techniques both interm of equipement and supplies needed and speed.
Bio-Rad's PowerPac™ Family of Power Supplies
This tutorial describes the features of Bio-Rad's PowerPac family of power supplies and compares their specifications. It also offers information about parameter selection, common error messages, and available PowerPac accessories. Important safety information is also provided.


Number Description Options
Protein Blotting Guide, Ver C
Western Blotting Detection Reagents Brochure, Rev F