  Effective force modulation during tissue manipulation is important for
ensuring safe robot-assisted minimally invasive surgery (RMIS). Strict
requirements for in-vivo distal force sensing have led to prior sensor designs
that trade off ease of manufacture and integration against force measurement
accuracy along the tool axis. These limitations have made collecting
high-quality 3-degree-of-freedom (3-DoF) bimanual force data in RMIS
inaccessible to researchers. We present a modular and manufacturable 3-DoF
force sensor that integrates easily with an existing RMIS tool. We achieve this
by relaxing biocompatibility and sterilizability requirements while utilizing
commercial load cells and common electromechanical fabrication techniques. The
sensor has a range of +-5 N axially and +-3 N laterally with average root mean
square errors(RMSEs) of below 0.15 N in all directions. During teleoperated
mock tissue manipulation tasks, a pair of jaw-mounted sensors achieved average
RMSEs of below 0.15 N in all directions. For grip force, it achieved an RMSE of
0.156 N. The sensor has sufficient accuracy within the range of forces found in
delicate manipulation tasks, with potential use in bimanual haptic feedback and
robotic force control. As an open-source design, the sensors can be adapted to
suit additional robotic applications outside of RMIS.
