Abstract:

The main target of this project is to design a FES based assistive device for MS affected people and to construct an Open-source, downloadable kit that will allow the personalized production of such device by any individual,

1. Project requirements :

(image of the electronic component)


- MecFes is an assistive device, of which the main function is to be integrated in a ADL activities and assist the users in tasks that involve the movement of the grip

- in order to reach this goal the device has to be designed in all it's dimensions including functionality, ergonomics, aesthetics end production. Succeeding in all thees dimension is a fundamental requirement for it's success.
- this project goal is to design an electrode applying structure that will be assembled with an already developed electronic component
let's look closely at every dimension:

Functionality:- device has to be mechanically resistant in order to maintain it's functionality with time
- major attention should be put to joints and other areas where high forces could be applied
- maximum of critical situations has to be studied in order to prevent breaking of components
- all mechanical components has to be precise and prevent possible mistakes of functionality

Ergonomics:


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- device has to be adopted to personal anthropomorphic measurements
- since users of the device are having different kind of motor impairment, it's of highest importance to consider thees particularities
- using the device has to be an easy and intuitive process, interactive parts and their purpose have to be evidenced
- minimization of volume and weight is required in order to be worn on the arm as low profile and comfortable device as required for activity and using it uordoors
- device have to be adopted for moving around while executing dynamic physical tasks without causing interaction with surrounding objects
- as a wearable, the device would have to be cleaned
- skin contacting materials have to be approved for such purpose
- different weather conditions and their impact on using the device have to be considered

Aesthetics:

- the device is intended to become a part of domestic landscape and outdoor activity of the user which determines a high request of acceptance for the user
- the aspect of customization is required in order to make a better emotional connection of the user and generate more motivation for the user

Production:- accessibility of medical devises is a big problem since their high price is caused by medical trials that are needed to approve the efficiency of the device,
new strategy of production and certifying is required
- production approach has to enable customization of the device while avoiding bulky adaptable solutions
- since the custom approach is required it's necessary to include the adopting process, when the necessary data of the user is gathered



2. General approaches


external image recreus-sneakers-i.jpgFDM 3d printing technology:






Nowadays 3d printing technology in involving more and more productive areas and it's specially interesting for the medical devices industry since:
- it gives a possibility to customize the devices for particular needs of the patient
- possibility to manufacture complicated, dynamic and ergonomic surfaces to feet the shape of the body
- rapid prototyping allows to create immediate solutions that can be tested to evaluate the concept







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OPEN-SOURCE and DIY :


Open-source is a modern busyness model that allows free sharing of the information or digital products in order to give others the possibility to express their creativity (DIY) of solve their needs .
why to use open-source technology for a medical device?

- sharing a project gives other possibility to contribute of their professional opinion
- shared project descriptions lets others to use it in order to create their own projects without wasting time on making same work, which accelerates the the efficiency of the projects
- because It's free, more people can build more projects
- because the target audience of the project are aware more then anyone about their needs and can contribute a lot with their own solutions that can be shared and integrated in an Open-source web of makers








3. First concepts

The main component of the object is the electrode bearing structure which has to be designed considering the possible behavior or the upper extremity, ergonomics and securiry.


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- the first concept of the structure was a rigid sleeve
- sleeve was cut in two half's in order to be enable it's opening and closing in order to put the forearm inside and then to lock the sleeve on the forearm
- electrodes were attached to Velcro strip
- the locking/unlocking movement which was a crucial point due to user's impaired movement, had to become as easy as possible
- as a simple solution, user would have to push down on the upper half of the structure on order to lock It to the second
- the hooks which are located on the both braces of the structures will lock the sleeve on the forearm

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-disposable electrodes were covered with leather, which have to be wet in order to function

- while using wet leather/ foam, electrodes are able to slide upon the skin wile maintaining electric contact, but they will need to be pushed passively to remain on the place and transmit electricity to the muscles



4. Evaluation and solutions

- the rigid structure is blocking the pronation of the wrist, movement that is used by some of target users to extend the palm
- it was decided to use dynamic structure that allows the relative rotation between the braces

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- the braces were connected by four bars
- the joint between the bar and the brace have to allow the relative movement (rotation and pronation)

- the relative rotation of the braces requires the variation of bar's length in order to maintain a constant distance between the braces
- the double hook locking mechanism gives a strong and secured lock, but its hard to open, easier solution will be needed
- the interior surface of the braces needs softening for ergonomic skin contact
- In order to maintain the electrodes in constant position






5. Second concept


after evaluating the first models, the next step was to define all the elements precisely and to produce the structure prototype using only 3d printed components
5.1 joints
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the key request for designing the joints was their grade of freedom between the brace and the bar. In order to enable the relative movement the bar will need to turn in all the axes.

It as decided to use the ball joint which gives maximum freedom, yet could be limited in motion for particular positions. in order to verify the validity of the solution 3d printing trials were made.

The final shape that proved itself as mechanically resistant enough was a solid sphere shape that had an inserting area on the internal part of the brace. The braces will be located on the brace's interior board.




5.2 bar length variation
Bar length would need to variate in max of 10mm. Such little length request was obtained by positioning the joint in the way that the bar wound be extended on its initial position(mounting position), this way it would shorten and then straighten again while it's rotating towards the final position(with palm upwards). In order to enable the variation of the length, the bar was divided in two components, one of which will slide on the inside of the other, this way the mechanism will be hided and won't cause any discomfort.


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.3 locking mechanism
As it was seen before, the hook to hook mechanism was a strong and secure solution which had an detaching issue.
It was decided to use a clip mechanism that maintains a strong holding effect and easy locking, while making the detachment easier

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5.4 unlocking action
As unlocking action It was chosen to use pulling movement, when the user pulls the bar of the structure towards himself. In order to pull the bar, user's fingers would need to inserted between the bar and the forearm.

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5.5 softening layer


The area of application of the softening layer are the interior surfaces of the braces. As a softening layer could be used any material, that is compatible with skin contact and has a softening effect, foam, textile, neoprene etc.


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5.6 electrode holders

since electrode bars are straight and are not attached to the skin, the electrodes which are positioned on the extreme of the strip needs to be somehow applied to the skin and held still in the determined position
In order to achieve this result, another component was developed. This component (electrode holder ) will tun around the bar, applying the electrodes to the skin when the hand while the forearm is being placed inside the structure

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6. Model 2 test with userA person with tetraplegia was asked to apply the model 2 to his hand, complying the actions of placing the hand, fastening the model, rotating the palm upwards and downwards and eventually unlocking the model and removing the hand


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6.1 –°onclusions
The user has succeeded to manage the prototype but there few complications were present

- upgrade of the fastening mechanism is needed in order to make the detaching movement easier

- more intuitive shape of the user interacting components in needed


7. Third concept

Third concept would have to solve the problems discovered previously and will combine the ergonomic solutions of the previous versions with the electronic components which have to be integrated with the structure, considering it's dynamic behavior


7.1 Model 3 test with user

7.2 Test conclusions

7.3 Exterior cover


8. Service strategy

Such innovative approach as open source and personalized 3d printing, requires a design of a new kind of service that will connect all the phases of the production.
The main phases are:

- person evaluation for being able to use the device and FES methodology

- measurements of individuals forearm

- inserting of the personal data in the adopted 3d soft in order to create a personalized 3d model

- printing 3d model using 3d printer

- ordering the electronics online

- assembling plastic model


- ordering the electronics online

- ordering the fabric component

- assembling the obtained model with electronics and with fabric component