Page 194 - Flexible Robotics in Medicine

Tendon routing and anchoring for cableriven single-t surgical manipulators 181

In a monopole electrocautery device, voltage is applied to its high resistance tip. When this tip
meets the tissue, current passes through the tip, and the heat generated at the tip causes the
contact point in the tissue to burn and effect a cut in the tissue. The high resistance tips were
separated from the main body and were anchored to a nonconducting plastic base that was
attached to the channels. An insulated copper wire of less than 0.2 mm in diameter was used to
transmit the voltage from the electrocautery’s main body to the tip attached in front of the
channel. Since copper is a particularly good conductor of electricity, the insulated copper wire
significantly reduces the loss of power over long distances and effectively transmitting all the
power to the electrocautery tip for it to be hot enough to cut the tumor. Although the monopole
electrocautery device integrated with our channel more naturally as the device had only on a
cable attached to high resistance tip, the cautery could only cut through the wet tissue since dry
tissue posed a high resistivity leading to substantially little or no current passing the tissue.
In contrast to the monopole electrocautery, the dipole electrocautery features two wires (positive
and negative) that are connected to a high resistance tip. When the electrocautery is activated,
current passes through the two wires and causes the high resistance tip to heat up, which is later
used to cut tissue. Since the high resistance tip has to be separated from the main body and
attached to the channel tip, two insulated copper wires were connected to the high resistance tip
and routed through the channel to transmit the current to the tip from the main body.
Furthermore, the high resistance tip is anchored to a channel through a nonconducting plastic
material to avoid the tip from breaking due to constant bending. Fig. 7.9 shows our modified
monopole and dipole electrocautery. Between the two types of cauterization, we choose to
implement the dipole architecture based on heatingcapacityand speedofcauterization.To
implement a dipole cautery, commercially available monopole electrocautery for acne removal
was modified so that it could be integrated with our 3 mm spring backbone. The resistance
module of the device was dismantled, and its wire routing method was isolated and modified.
Integrating FeCrAl alloy wires at the tip of the device is to produce heat to burn a tumor.
Finally, the circuit was completed using copper wires, which run through the spring backbone
such that the electrical input supply can be provided from a distal end.
After the modification of our instruments, we integrated them with the tendon-driven
actuation mechanism of our flexible spring backbone. Fig. 7.10 shows our overall integrated
single-port multichannel end-effectors.

Figure 7.9
Modified electrocautery integrated into a 3 mm flexible spring backbone.