Final Update

1) What we planned to get done this week.
This week, we planned to build a final functioning prototype, print the final puzzle pieces, demonstrate the use of the temperature-sensitive paint, and wrap up with our final presentation. Depending on our progress with the circuit, we were also considering cutting printed circuit boards that were specific to our needs.

2) What we actually got done this week.
We were successfully able to get a signal from human contact using the oscilloscope and alcohol-based hand sanitizing gel. We also printed a new and improved version of the puzzle piece lay out. We started with this last week:



And ended with this as our final prototype:








The final version is a single, compact and connected unit that features aluminum contacts between the modules. It is powered by a single 9V battery, which will replace the four 1.5V batteries that were formerly connected in series. It also contains a small green LED in each electronic module that would eventually be used for self-diagnosing purposes in the case of system failure. Overall, we’re pretty excited about our progress this week!

Exciting News on the Circuit

We can get a signal from a person! Well... kind of. See the series of pictures below for what I mean:

The circuit in its current form, color-coded to indicate how we will modularize it.













The signals shown above were generated using pennies as leads. One penny was placed on the "patient's" chest, near the heart, and the other was held in the "patient's" hand. The figure on the left shows the signal detected by the oscilloscope when the leads were not in place. The signal on the right shows the signal detected when the leads were on the chest and hand, respectively. While these results are exciting, it requires a lot of trial-and-error of lead placement. Perhaps this finicky-ness will improve once we attach our own leads and use conducting gel.

5/4-Abstract

During our visit to a rural health center near Ocotal, we spoke with a physician who articulated the desire for an EKG and other tools to allow him to diagnose heart problems. This made us aware that smaller, more remote facilities are interested in this technology but lack the appropriate resources to obtain and use them.

Our device is a user-friendly, modular EKG device that functions via the standard input of cardiac electrical signal (using metal leads) and outputs an electrical signal that can be viewed on any device with an LCD, such as a computer monitor, oscilloscope, or potentially a mobile device.

Our device is unique because of its use of discrete (but connectable) circuit modules, each of which performs a single function and contributes to the overall function of the machine. Additional features include a temperature-sensitive indicator that informs users when any module exceeds the optimal operating temperature and a method of broadcasting the signal to a local device via bluetooth or a wireless signal.

Our project addresses a need for cardiac diagnostic tools by allowing health practitioners at all levels to record diagnostically useful information about cardiac health and to transmit that information to specialists.

Weekly Update

1) What we planned to get done this week.
This week, we planned to build a functioning circuit and to begin building the pieces that would go into modularization (i.e. the puzzle pieces). Depending on our progress with the circuit, we were also considering cutting printed circuit boards that were specific to our needs.

2) What we actually got done this week.
We 3D-printed two puzzle pieces (see picture below) whose shape and size was based on plastic boxes that we tentatively plan to use (final design will depend on the circuit pieces). These have space to accommodate connecting wires and will eventually serve as self-sufficient circuit modules that, when connected together, will result in a functioning and whole device. We also 3D-printed a lead connector. There are improvements to be made to each of these initial prototypes, and we will need to make more depending on the final structure of the circuit, but it was helpful to have actual pieces to work with.
We’ve identified four component that are necessary for a complete and functioning circuit: an input, which could consist of the leads or a microprocessor that generates an regular EKG signal, a band-pass filter to eliminate noise below 5 Hz and above 44 Hz, and an amplifier to produce the final signal, which can then be transmitted via audio jack to a device with an LCD screen that can display the signal. We’ve decided to segment our device into 4 puzzle pieces (this may end up being 5 depending on the ease of connectivity with 4). We’re also considering isolating the op amp as its own component, given the fact that it is the most likely to stop working of all the circuit elements that we’ll be using (it’s the most sensitive to temperature).



3) What we plan to get done this week.
This week we plan to build a final, functional form of the circuit, print circuit boards for each of the pieces, and connect them using the puzzle pieces, which will allow for specific and appropriate metal contact. We also plan to wrap up our final presentation and grant application components.

Monicor Evaluation

As we approach the end of the term, we would like to define our criteria for evaluating our concept to see if it is achieving the desired outcomes.

First, our design must be modular. The complexity of the device must be compartmentalized. If we can achieve this, then our users will have a much greater degree of ownership over the technology than over comparable devices in our domain. Our end users will be able to fundamentally understand the functionality of the EKG from the ground up. Additionally, they will be able to modify the design to best fit their specific situation and repair the device should any problems occur.

This leads to the next design criterion of making problems visible. If a modular component should fail, then our end users (doctors and nurses) should be able to identify what went wrong. Either by thermochromic paint or by electrical indicators, there needs to be an unambiguous sign that shows where the problem is happening so that the proper repair can be made.

The ultimate design must also efficiently use resources and must be able to be produced fairly easily. Cost parameters should be minimized while making sure that the components of our EKG device can be manufactured in bulk.

Building Blocks

A diagram of the puzzle piece design is above. Right now it's designed to fit a 2inX2inX3/4in box, and it allows for metal contacts to be made easily through an interlocking "snap mechanism". We should have one printed late tonight or tomorrow, so we'll see how effective it is at providing the appropriate contacts.





This is a Sketchup model of two pieces that are positioned to interlock and a SolidWorks model of a single piece.



Here is the piece that can connect a wire on the circuit to the top half of a metal sewing snap. This piece will also be 3D printed.

D-Lab Design Reviews