Solid Media Transmission

An Innovative and Versatile Transmission

What Is the Solid Media Transition and the motivation behind its invention.

After our earlier work in developing MR compatible interventional robots (esp the one for breast and the other for abdominal/spinal interventions) we formed a vision about the next generation of MR compatible robots from our Lab, Within this context, the Solid Media Transmission (SMT) was conceived at the early stages of constructing a robot for intracardiac interventions as part of the MIROS CPS (an NSF funded project). In response to the criteria listed below, the fluid medium was substituted with spheres and then spacers were added in-between them for improving efficiency.

Our Criteria for the Next Generation MR Compatible Manipulators:

• Do Not Use Ultrasonic or Hydraulic or Pneumatic motors: Use Conventional shielded, filtered and/or secured Electromagnetic Motors (EM) positioned outside the gantry

• Connect the EM's to the robot To Degrees-of-Freedom (DoF) with some form of tranmssion that is easily flexible and adjustable like the fluidic transmissions (hydraulic or pneumatic) but do not use fluids!

• In general, make them such that no special Preparation or changes are needed the MR scanner Room: Place the robot control electronics inside the MR room (shielded) and ecven avoid using the filter plate (if such exists!)

Features of SMT

SMT technology can reduce production cost and complexity and avoid other disadvantages of alternative methods (ultrasonic or fluidic actuators). SMT has the key properties of fluidic actuators (remote actuation and flexible routing), while exhibiting certain unique key features:

• Fluidless: This key feature has far reaching consequences in the design of SMT-actuated devices in regard to compactness and mechanical simplicity:

(1) it does not require an actuation piston that is at least as long as the stroke, and

(2) actuation can be transmitted from the SMT media to the actuated component, or vice versa) at any location via slots in the channels or tubing.

• Flexibility in design and production: Secondary to its fluidless feature, SMT offers new opportunities for alternative and simpler designs, and production. For example, straight and curved SMT channels can be embedded into the frame of a manipulator, which can be produced by CNC milling or 3D printing two layers and then bolting them together (See designs, videos, manuscripts and patents).

• Environmentally versatile: Without the need for hydraulic fluids, SMT is well-suited for any application where leaks and hydraulic contamination are undesirable. In addition, it can be made less prone to environmental conditions. This opens opportunities in special industries such as the aerospace and oil/gas that require systems to function in near-vacuum, at cryospheric temperatures, or in high-pressure subsea conditions.

MK2: A 1-DoF SMT Bot - our early workhorse

The MK2 is a linear stage, a 1 DoF SMT-actuated manipulator used in experimental studies to systematically investigate and characterize the operation of the novel SMT.

Representative SMT Characterization Studies

MK3: A 4 DoF Parallel SMT Bot

This robot is a wonderful manifestation of how the SMT can be realized fo a complex 4 DoF parallel kinematic architecture entailing a plurality of innovations on how to engage and link and engage 4 bi-directional SMT lines to 4 independent DoF: two rotational and two linear.

Video of 3D Design (Left): the primary components of the MK3 SMT-Bot with a unique way of implementing the parallel kinematic structure: each plane contains a rotational DoF (actuated by one bi-directional SMT) and carries a linear one onto which is attached the interventional tool via passive bearing. What is exciting is that the linear DoF is also actuated by a highly innovative rotational DoF! Photos (middle and right): the MK3 SMT-Bot carrying a biopsy needle.

Some SMT Modeling with Mathematica

Some wonderful simulations by our colleagues Haoran Zhao and Aaron T. Becker

Compression Ratio of Spheres in a Curved Tube

Transmitting Force through a Tube Filled with Spheres and Spacers

SMT-Bots, Electromagnets and ... MRI, how do they fit?

SMT is composed of media (spheres, spacers & conduits) made of non-magnetic/ferrous material; as a consequence its presence and media actuation does affect the generation of MR images (no noise or signal artifacts, non-linearities or inhomogeneities).

We did use conventional EM (made by Maxon; seen in the photos above) placed outside the 5 Gauss line and eventually were proven quite MR safe & compatible:

• no force was exerted on the motors sufficient to dislocation (motors + SMT-specific pistons manufactured of aluminum).

• the power supplies and controllers were placed in an EM shielded box (see figure below) that sufficient to preserve the SNR when the motors were ON and operating in open or closed loop control. The closed loop controller was running on the Unit.

The Control Unit was inside the MR scanner room and was powered by a wall power outlet.

The User Server (that runs the .MR-based servoing or path planning) it connects to the Control Unit via an optical cable and can reside inside (beyond 5G) or outside the scanner room. During robot operation, from the Unit receives a stream of optical encoder signals, commands sent to the controllers from closed/open loop. It sends to the Unit, commands to actuate the closed/open loop

Our conclusion was that, with appropriate measures, conventional EM motors can eb used tinside the MR scanner room, and controlled to actuate an SMMT-powered robotic manipulator inside the gantry of the MRI scanner

NSF STTR Funding

NSF STTR I 1622946 Award Page

Announcement of the NSF STTR Award that supported the further development of this technology

UH Startup Earns Commercialization Grant for New Technology

The People

A great team of amazing Engineers and Scientist worked closely under the support of the support of an STTR NSF and brought this project to fruition:

Dr. Michael J. Heffernan, PhD; a great Scientist with superb Management abilities and experience

Prof. Aaron Becker, PhD; a true Engineer who run the Engineering

Dr. Haoran Zao, PhD, a ECE who did modeling, simulations, construction and testing

Dr. Xin Liu, PhD; a CS who both running extensive experimental studies and developed software for MR servoing and path planning; a software engineer who learned MRI, robotics and their combination!

Mr Korpu who contributed major effort in bulding, assembl;ing and texting

Ms Yolanda who volunteered a her expertise and time in 3D designing!

The different aspects of this work were supported in part by the National Science Foundation Grants CNS-0932272, IIP-1622946 and CNS-1646566. All opinions and conclusions or recommendations expressed in this web page k reflect the views of authors not our sponsors.