**1.1 Robotic assisted minimal invasive surgery**

An alternative to traditional minimal invasive surgery is robot assisted minimal invasive surgery. Many disadvantages of manual MIS are overcome with robotics:

Sensorized Tools for Haptic Force Feedback in Computer Assisted Surgery 135

(Daubeney et al., 2005) using fetoscopy (Sydorak and Albanese, 2003), consists of a steerable and flexible catheter equipped with a fiber optic reflectance sensor for color detection, 4 electrodes for bio-impedance spectroscopy and a patented washing system (patent Sieber et

Next to force sensorized tools, haptic force feedback input devices are a key element for future computer aided surgery. One approach is to use visual force feeback. A study (Reiley et al., 2008) was carried out demonstrating that visual force feedback offers benefits like reduced suture breakage, lower forces, and decreased force inconsistencies; however it was concluded, that these benefits are mainly an advantage for novice robot-assisted surgeons

Song et al. (2006) have developed a laboratory set up for haptic force feedback tele-operation consisting of a 6-DOF robot and a commercially available haptic force feedback input device (PHANTOM Omni). Forces on a tool (like a blade) were acquired with a 3DOF force sensor. A different group proposed to incorporate haptic force feedback into the ZEUS system by integrating a PHANTOM input device (Ortmaier et al., 2001). Another PHANTOM based system was discussed in (Tavakoli et al., 2003). In the PHANTOM haptic force feedback system, force feedback is generated with DC motors that apply a torque on the joints. Similar, but very simplified, technology is used in haptic force feedback joysticks for gaming, where the position of the joystick is acquired with 2 potentiometers and force

For our work with the sensorized microgripper (Houston et al, 2011) we have developed a force feedback haptic tweezer. In contrast to the operating principle of the PHANTOM and haptic force feedback joysticks, the haptic tweezer is an active servo actuated tool, where the force on the tweezer is measured with a strain gauge and the tweezer is moved actively in a closed control loop. Advantages are precise movement control and low manufacturing costs. In the third part of this chapter a novel haptic force feedback joystick is described which derives from the haptic tweezer. The force on the joystick is measured with strain gauges and the joystick is actuated with servos in a control loop. The same principle can be

The methods section comprises three of our latest developments: a force sensorized cutting tool (described in Section 2.1), a steerable force sensorized catheter with haptic force feedback for fetoscopy (described in Section 2.2), and a novel joystick with haptic force feedback (described in Section 2.3) which can be used as haptic force feedback input device

Typical cutting forces in surgical interventions can reach values of up to ±3N for tangential and 10N for normal loadings. The device described in (Valdastri et al., 2005) uses a siliconbased MEMS sensor to measure forces on a cutting blade. The MEMS sensor deployed in the

al., 2007) to enable optical measurements in the presence of blood.

**1.3 Haptic force feedback input devices** 

and diminishing benefits among experienced surgeons.

feedback is generated by the torque of a DC motor.

**2. Methods** 

**2.1 Force sensorized cutting tool** 

used for designing low cost haptic input devices with 3 or more DOFs.

for the control of the sensorized cutting tool as well as the sensorized catheter.


State of the art robotic assisted surgery systems like the Da Vinci System (Intuitive Surgical, (California, USA) enable minimal invasive incisions thus offering a more conservative alternative to standard open surgery. Unfortunately, due to the lack of haptic force feedback, these systems can only be used in cases where the visual information is enough and haptic sensing is not needed (Wagner et al., 2002). Often surgeons and robotic researchers point out this fact as major limitation of robotic aided surgery (Mohr et al., 2001) (Cavasoglu et al., 2003).

A key element for enabling haptic force feedback robotic or computer assisted surgery are force sensorized tools:

"Smart medical tools" often stands for sensorized devices (Dario et al., 2003). One example are catheters with integrated pressure sensors (Strandman et al., 1997, Kalvesten et al., 1998, Melvås et al., 2002) which are mainly for diagnostic purposes, but not for surgical interventions except in the combination with so called balloon dilation for cardiac vessel expansion.

Sensorized microgrippers are described in (Houston et al., 2007). In these grippers micro strain gauges are integrated into the polymer arms, thus an accurate and precise gripping force monitoring and control is possible. On the basis of this gripper, an endoscopic tool for robotic aided surgery was developed (Houston et al., 2008) where a wire driven joint (Harada et al., 2005) allows rotation of the gripper.

Robotic aided surgical interventions where precise cutting tasks have to be performed are quite difficult – one main reason is again the lack of haptic force feedback. One approach to deal with this problem is to equip tools with Micro Electrical Mechanical Systems (MEMS) (Rebello, 2004). A force sensorized microsurgical tip is detailed in (Berkelman et al., 2003). A first prototype of a cutting blade based on a triaxial MEMS force sensor (Beccai et al., 2005) was presented in (Valdastri et al., 2005). With the help of an advanced assembly process (Sieber et al., 2007) the MEMS sensor could be directly mounted on a flexible substrate – which allowed a further miniaturization of the sensorized cutting device as detailed in (Valdastri et al., 2007).

## **1.2 Sensorized catheters**

Another topic addressed in this chapter is the development of sensorized tools for catheter based minimal invasive surgery. One example of a smart catheter is the recently developed TactiCath® [Endosense, Switzerland]. It is an ablation catheter, that is equipped with a force sensor to provides real time contact force measures (Vijaykumar et al., 2011).

Especially during catheter navigation through thin vessels, that can easily be damaged, haptic force feedback can improve largely the safety of such interventions. A recent approach of a "smart tool", developed especially for treatment of pulmonary atresia (Daubeney et al., 2005) using fetoscopy (Sydorak and Albanese, 2003), consists of a steerable and flexible catheter equipped with a fiber optic reflectance sensor for color detection, 4 electrodes for bio-impedance spectroscopy and a patented washing system (patent Sieber et al., 2007) to enable optical measurements in the presence of blood.
