Delft Cylinder Hand, Prosthetic Devices

Natural grasping

Background
Replacement of a missing hand by an artificial alternative remains one of the biggest challenges in rehabilitation. Although many different terminal devices are available, around 27% of the amputees does not actively use their device and 20% totally refrains from wearing it. There are various reasons for prosthesis abandonment, e.g. wearing discomfort (too heavy, too hot), too little added functionality, difficult or tiring to use, lack of sensory feedback. User studies identified multiple aspects of the prostheses that need improvement, in order to meet the user demands. Mass reduction was identified as the most important design priority.

Goal
The goal of this project is to design and test a new lightweight and efficient body-powered hand prosthesis with articulating fingers. A low mass will increase wearing comfort. Mechanical efficiency will decrease the required actuation force, which will lead to an increased control comfort. It will also enable the hand to produce a higher pinch force, which will increase the functionality of the hand. The articulating fingers of the hand will enable both power and pinch grip. This enables the grasping and holding of a broad range of different objects and enhances natural cosmesis.

The Delft Cylinder Hand appeared in the corporate movie of the Delft University. Click the video below.

Delft Cylinder Hand
During this project a new prosthetic hand prototype was developed, the Delft Cylinder Hand. It has under-actuated articulating fingers which adapt to the grasped object. It has voluntary closing body-powered control and it has a hydraulic cylinder transmission. The hand was subjected to various mechanical and functional tests. Through the application of a hydraulic transmission, the hand requires 49-162% less energy from
the user when compared to commercially available body-powered hands and it has a higher maximum pinch force (30-60 N). In functional tests the hand scored similar to current myoelectric hands. Yet its mass (152 gram without glove; 217 gram with
glove) is 68% lower than the lightest available articulating myoelectric hand and 55% less than the lightest body-powered hand of similar size. Functional tests showed that The ‘Delft Cylinder hand’ provides the amputee with a level of function that is at
least comparably to contemporary hands, at a cost (mass and actuation effort) which is much lower than that of all currently available hands.

Adaptive grasping
The Delft Cylinder Hand was developed to enable natural grasping of small and large objects. The hand can perform fine pinch grasp, as well as cylindrical power grasp, required to pick up a suitcase.

The following video shows some examples:

The Delft Cylinder Hand has articulating fingers and is anthropomorphic, slender, fast, efficient and silent. The hand mass is much lower than the lightest commercially available hand. The hand therefore meets one of the most important user demands in
upper limb prosthetics, which is a low hand mass. The hand can pinch harder (>30 N) at a lower user effort.

 

More research on prosthetics: DIPO website

Watch the TEDxTalk on the Delft Cylinder Hand

Biopsy Harvester

Biopsy Harvester – High-Speed Tissue Cutting

Current minimally invasive laparoscopic tissue harvesting techniques for pathological purposes involve taking multiple imprecise and inaccurate biopsies, usually using a laparoscopic forceps or other assistive devices. Potential hazards, e.g. cancer spread when dealing with tumorous tissue, call for a more reliable alternative in the form of a single laparoscopic instrument capable of repeatedly taking a precise biopsy at a desired location. Therefore, the aim of this project was to design a disposable laparoscopic instrument tip, incorporating a centrally positioned glass fibre for tissue diagnostics; a cutting device for fast, accurate and reliable biopsy of a precisely defined volume and a container suitable for sample storage.

Inspired by the sea urchin’s chewing organ, Aristotle’s lantern, and its capability of rapid and simultaneous tissue incision and enclosure by axial translation, we designed a crown-shaped collapsible cutter operating on a similar basis. Based on a series of in vitro experiments indicating that tissue deformation decreases with increasing penetration speed leading to a more precise biopsy, we decided on the cutter’s forward propulsion via a spring. Apart from the embedded spring-loaded cutter, the biopsy harvester comprises a smart mechanism for cutter preloading, locking and actuation, as well as a sample container.

A real-sized biopsy harvester prototype was developed and tested in a universal tensile testing machine at TU Delft. In terms of mechanical functionality, the preloading, locking and actuation mechanism as well as the cutter’s rapid incising and collapsing capabilities proved to work successfully in vitro. Further division of the tip into a permanent and a disposable segment will enable taking of multiple biopsies, mutually separated in individual containers. We believe the envisioned laparoscopic opto-mechanical biopsy device will be a solution ameliorating time demanding, inaccurate and potentially unsafe laparoscopic biopsy procedures.

 

Publications

Dendritic Instruments, Steerable Instruments

NWO VICI – Dendritic Instruments – Outreaching the Squid

This VICI-research project is funded by the Netherlands Organization for Scientific Research NWO.

Background

In ‘standard’ minimal access surgery, the surgeon inserts rigid instruments through small incisions in the skin or natural orifices to reach targeted areas inside the human body. This approach drastically reduces the invasiveness of surgery compared to conventional open approaches, yet the reduced size of the surgical entry-point does also severely restrict the maneuverability of the used instrumentation. This lack of instrument maneuverability becomes especially apparent when considering Endoscopic Skull Base Surgery (ESBS). A prime target of ESBS are tumors on the pituitary gland positioned at the skull base, the region that separates the brain from the rest of the head. The nose is used as the surgical entry-point, and due to the rigid nature of the used instrumentation, the surgeon needs to create a straight surgical pathway to the pituitary gland. The limited width of this pathway in combination with the need for multiple instruments severely limits sideway movements of the instruments. This situation leads to a phenomenon called swordfighting wherein the shafts of instruments collide and, moreover, it severely restricts the maneuverability of the individual tools (i.e. grasper, scissors, etc.).

We strive to improve on overall instrument maneuverability with the development of dendritic instruments. A dendritic instrument is a maneuverable single-shaft instrument that branches into multiple independently steerable tools. Such an instrument would eliminate the occurrence of swordfighting, as the number or shafts is reduced to one, while providing the surgeon sufficient maneuverability of the individual tools. This research project is divided into two main topics; the mechanical construction and methods of control of dendritic instruments, such that these instruments are able to be implemented in operating theatre in the near future.

Steering

The mechanical construction of a dendritic instrument consists of two basic parts. First, there is the shape memory shaft that should be capable of following a curved trajectory up to the targeted area while providing a stable base. Secondly, there are the individual steerable branches that sprout from this stable base and provide independent maneuverability of each individual tool.

Creating a steerable branch starts with a flexible structure, either containing joints or a compliant backbone. The actuation of such this flexible structure can then be realized by several actuation methods, including the use of electric motors, hydraulic actuators, and shape memory alloys. Our research is focused on a fully mechanical actuation method based on cable-structures. This allows for structures that are easy to miniaturize, eliminates the need for possibly dangerous electric currents, high pressures or high temperatures, and shows high potential for reducing the costs of fabrication.

Besides the obvious requirement that the branches need to be maneuverable, they should also have a certain stiffness in order to cope with external forces that will be present during, for example, tissue manipulation. In our search for a suitable cable-structure to achieve high maneuverability and stiffness, we have developed a cable-structure in which multiple cables are placed at different angles along the longitudinal axis. This structure has already shown great promise and is now in the process of further optimization.

Control

Dendritic instruments consist of many small joints and branches which the surgeon(s) needs to actively steer, in order to perform complex surgical tasks (e.g. suturing or tissue manipulation). The amount of joints in dendritic instruments are even so many, that currently existing prototypes require the cooperation of two surgeons to perform a task which is actually meant for only one surgeon. In other words, dendritic instruments have more Degrees of Freedom (DOF) than any  surgeon can control alone. However, the large amount of DOFs combined with an intuitive method of control is exactly what is required for dendritic instrumentation to become a reality.

The BITE research method to dendritic instrument control is one which is exploration driven. The optimal mechanical construction and DOF configuration are still being researched. Hence, the accompanying control interface or instrument handle cannot be designed yet. To investigate the best methods of control, virtual instruments are simulated in a Virtual Environment (VE). Physical hand movements and gestures are measured with RGB-D Kinect cameras, and mapped to virtual instrument movements. By playing with the coupling between hand DOF and instrument DOF, new control strategies are tested and reverse engineered to ultimately discover the best method for dendritic instrument control.

Dendritic_control_simulation_setup

Image adapted from  www.nimblevr.com (previously www.threegear.com)

I-Flex, Steerable Instruments

I-Flex – Steering Towards Miniaturization Limits

Developed in 2007-2008, diameter 0.9 mm, steering range: ±90º in all directions.

The retina is a light-sensitive layer at the inside of the eye. The macula is the region at the center of the retina with the highest concentration of light-sensitive cells. Macula degeneration – a disease which is a major cause of blindness –  is caused by a disfunctioning choroid layer under the macula. A way to treat macula degeneration is to perform surgery to the choroid layer via a tiny incision in the retina near the macula.  Reaching the choroid layer under the macula is extremely difficult as the surgeon has to operate through the incision under an angle while avoiding damage to the extremely delicate macula layer.  A steerable instrument could potentially solve this issue by making it easier to steer the instrument through the incision.

The largest design and fabrication challenge of such an instrument is the extreme miniaturization of the steerable mechanism in the tip. Down-scaling our patented Cable-Ring mechanism, already applied in the Endo-Periscope III and MicroFlex, to a very small scale, resulted in the  I-Flex – world’s smallest steerable surgical instrument that can be steered in all directions. The compliant tip has a diameter of only  0.9 mm and is constructed from 7 steel cables and a spring. Being equipped with a tiny gripper, the tip can be steered in two Degrees of Freedom (DOF). The instrument contains a novel handle that combines intuitive steering with a fine and precise pincer grip.

Feedback of experienced eye-surgeons from the Eye Hospital in Rotterdam has led to the development of a second prototype which is currently under construction. This instrument incorporates a different handle, allowing further miniaturization of the steerable tip to a diameter of only 0.45 mm – three times the size of a human hair.

 

Publications

Media

Endoscope Shaft Guidance (closed)

Shaft Guidance for Flexible Endoscopes

Flexible endoscopes (long, slender, flexible instruments with a camera and light at the distal end, having working channels to introduce flexible instruments) are used for diagnostic and therapeutic interventions inside the human digestive system and inside the abdomen. Though used for their flexibility, the flexibility of these instruments causes several difficulties during insertion and use. During insertion, flexible endoscopes can buckle and loop, which may hamper full insertion into the patient’s body. During therapeutic interventions, the flexible endoscope fails to provide stability for surgical instruments that are introduced through the flexible endoscope.

Shaft-guidance would be a good solution because it potentially enables following a 3D trajectory without any support of the surrounding anatomy at all. Combining auto-propulsion with a rigidity control mechanism may provide improvement in applications within confined anatomies where auto-propulsion simplifies insertion and rigidifying the endoscope shaft helps to stabilize the instruments during surgery. Three potentially suitable rigidity control concepts are selected and further investigated to quantitatively and qualitatively predict the maximally achievable flexural rigidity of these rigidity control mechanisms:

– Vacu-SL

– FORGUIDE

– PlastoLock

The thesis on this topic can be found on:
Shaft-Guidance for Flexible Endoscopes

 

Endoscope Shaft Guidance (closed)

FORGUIDE

The FORGUIDE mechanism enables making a shaft-guide out of cheap standard parts that is rigidified by creating a laminate that consists of a spring, cables and expandable tube. The connection between these three layers is obtained by friction. The bench tests showed that the FORGUIDE prototype FGP-01 of only 5.5 mm diameter could provide flexural rigidities up to 1541 Ncm2 , which far exceeds the flexural rigidity of flexible endoscopes. Furthermore, a bending radius of almost 1 cm could be achieved in the compliant state with the FGP-01 without losing the ability to rigidify.

MultiFlex, Snake-like Instruments

MultiFlex – Tentacle from Steel

 

 

Developed in 2008-2009, diameter 5 mm, steering range: ±200º in all directions.

The MultiFlex is what we call a multi-steerable instrument. Based on the Cable-Ring mechanism applied in the Endo-Periscope III, the MultiFlex does not contain just one, but five steering segments serially stacked on top of each other. Each of these segments can be actuated in two Degrees of Freedom (DOF) by its own set of four steering cables, resulting in a total of 20 steering cables and a 10-DOF maneuverable tip capable of making a wide range of 3D shapes and curves. This level of maneuverability gives the instrument the ability to steer around anatomic strucures, making it world’s first instrument of this kind developed at 5 mm dimensions.

By using the Cable-Ring mechanism, all actuation cables could be positioned at the same diameter. Consequently, the increase in maneuverability does not affect the outer diameter of the instrument, which is still equal to Ø5 mm with a complexity similar to the Endo-Periscope III. The control handle of the MultiFlex has a  structure similar to the tip, yet its dimensions are scaled-up for a better fit to the surgeon’s hand.

 

Publications

Media

 

Control Devices, EndoPAC

Endo-PaC – Endoscopic Path Controller

Developed in 2011-2012.

In the field of minimally invasive surgery and specifically in pathway surgery – i.e. minimally invasive procedures carried out transluminally or through instrument-created pathways – spatial disorientation is a common experience to surgeons.

Our Endo-PaC (Endoscopic Path Controller) is a simulator designed to investigate human control behavior during path following tasks. Emulating the shaft and handle of a maneuverable surgical instrument, Endo-PaC’s hardware controller consists of a base, an instrument shaft, and a handle with a joystick. The hardware controller contains five position sensors to measure the orientation of the shaft relative to the base, the translational displacement of the shaft, and the orientation of the joystick relative to the shaft. Instead of having a separate joystick, the handle can also be directly connected to the joystick, making the Endo-PaC suitable for comparing thumb control with wrist control.

The hardware controller is combined with custom-developed software animating surgical pathway scenarios. This virtual environment enables the assessment of the user performances based on criteria such as task completion time, motion smoothness, collisions, and the length of the travelled path. This makes the Endo-PaC highly suitable for comparing different control techniques.

Publications:

Steerable Guidewire

Steerable Guidewire – Maneuvering without Twisting

Developed in 2007-2008, diameter 0.9 mm, length 1 m, steering range: ±90º in all directions.

The Steerable Guidewire has been developed by spin-off DEAM in a very close collaboration with the BITE-group, using our patented Cable-Ring technology. Intended for easy steering through a network of blood vessels during catheter interventions, the guidewire contains a flexible shaft ending in a steerable tip with two Degrees of Freedom (DOF). The mechanism is novel as compared to existing guidewire designs in that it requires no need for twisting the guidewire body for re-directing the tip, which results in a much more stable and fluent 3D steering motion. The tip-mechanism is similar to the I-Fex and composed out of seven steering cables surrounded by a spring. The handle contains two joysticks, one at the proximal handle side and one at the distal handle side, that can both be used to control the 2-DOF tip. The Steerable Guidewire forms the basis for a series of new multi-steerable catheters designs currently being developed in the BITE-group.

 

Publications

Media

Endoscope Shaft Guidance (closed)

PlastoLock

Flexible endoscopes are used for diagnostic and therapeutic interventions in the human body for their ability to be advanced through tortuous trajectories. However, this very same property causes difficulties as well. For example, during surgery a rigid shaft would be more beneficial since it provides more stability and allows for better surgical accuracy. In order to keep the flexibility and obtain rigidity when needed, a shaft guide with controllable rigidity could be used. On this page we introduce the PlastoLock shaft-guide concept, which uses thermoplastics (Purasorb PLC 7015) that are reversibly switched from rigid to compliant by changing their temperature from 5 to 43 degrees Celcius. These materials were used to make a shaft that can be rendered flexible to follow the flexible endoscope and rigid to guide it.  A feasibility study shows the great potential of this concept in terms of achievable flexural rigidity, miniaturization, and simplicity.

Solving medical problems through nature’s ingenuity