Bloodbot automatically detects and withdraws your blood

by Priya Ganapati | Submitted Monday Sep 14, 2009 [11:00 AM]

Bloodbot, a prototype robot for taking blood samples, developed by Dr Alex Zivanovic and professor Brian Davies at Imperial College London, 2001.

An active robot designed in 2001, the Bloodbot is tasked with taking blood samples from an area in the crease of the arm. Simple as that sounds, the Bloodbot’s biggest challenge is in finding a vein, since the pattern of veins varies across individuals.

To avoid a bloodbath in its quest for a vein, the Bloodbot presses a probe against the surface tissue and measures the force on the probe. The pressure difference across the area indicates the presence of a vein. Once the Bloodbot finds a vein it inserts a needle and draws the blood. The system is sophisticated and precise enough to ensure that it doesn’t insert the needle too far into the vein or overshoot the vein. Three powered axes and one powered rotational axis make up this robot — a relatively simple design compared to others in this gallery.

Motion Control
The Bloodbot has three powered (linear motion) axes and one unpowered (rotational) axis. All the motors are inexpensive stepper types.

The first axis moves a carriage up and down, so that it goes towards and away from the arm that is strapped in under it. This carriage is used to hold either a blunt probe (for finding a vein) or a syringe and needle. A piezo-resistive force sensor is mounted on the carriage to measure the force on the probe or needle.

The second axis moves the carriage across the width of the arm. This enables the probe to press in a series of places along the width of the arm.

The third axis, which is unpowered, enables a human operator to tilt the robot. This is so that, once a vein has been found, the needle can be inserted into the arm at the correct angle.

The fourth axis moves the whole robot along the length of the arm. This was designed to compensate for the slight difference between where the probe has identified a vein, and where the needle enters the skin, once the robot has been tilted.

Validating the Design
The system was tested on the phantom arm and the results obtained were consistently good.

The ideal situation would have been to test the system on a wide range of patients. However, because of the difficultly in obtaining permission to test medical devices, the system was tested on only one human patient. The vein location phase was tested on the patient and the vein was located correctly about 78% of the time. The needle insertion was also tested and worked. This test was not repeated, so as to avoid multiple scarring.

More tests need to be carried out on a wider range of patient types (elderly, infants, obese, etc.) to more accurately determine the performance of the robot and to enable further developments to be carried out.

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Tags:blood  surgical+robot  needle  medical+robotics 

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