Project Development

A page for tracking development of the final project

To see the final product and a step-by-step guide to fabricating, please visit my Final Project page.

Below is the messier, but more complete development process.

Complete your final project, tracking your progress: what tasks have been completed, and what tasks remain? what’s working? what’s not? what questions need to be resolved? what will happen when? what have you learned? Project management: Murphy’s Law 80/20, 95/5 triage documentation during development demand- vs supply-side time management spiral development, DevOps serial vs parallel tasks system integration finish quality

Ideation

Can I create a tool to elicit understanding an ease fear? To provide a moment of clarity and wonder and distraction?

For my final project I’m aiming to create:

A heart model which can be used to communicate and educate patient-families about normal heart anatomy.

I want to embed and program lights within the model to illustrate the way blood moves through the heart in a way which is immediately digestible to viewers. I also want it to be an object of beauty, something that draws the eye and captures the attention, so it’s enjoyable to learn from.

Corazon X Luce = Illuminazon

Spiral Development mapped onto Fab Academy Schedule

Written in collaboration with ChatGPT.

Week 01 - Project Management, Inital Final Project Ideation:

• Begin ideation about final project: scope, sketches, goals, and objectives.
• Create a detailed project plan with milestones, tasks, and deadlines.

Final project idea: A light-enabled 3D heart teaching model which can provide overwhelmed parents of all backgrounds with a baseline understanding of normal heart anatomy and function.

Also see Week 1.b: Principles & Practices

There are already a number of plastic 3D heart models available on the market, available in a range of colors, materials, sizes, and prices. Some have removable sections which reveal the inner structures and connections of the heart.

Some clinicians already use static models such as these during consults with patient-families, some draw 2D sketches, but in general there isn’t a set “way” that all clinicians handle this conversation.

I would build upon the normal heart teaching models currently available by integrating light into the wall/inner surface of the cardiac chambers which could be programmed to illustrate the flow of blood in a physiologically normal heart. I’m envisioning a model fashioned out of a partially opaque material (3D printed? molded & casted?) for a diffuse light scattering effect. A network or mesh of tiny lights embedded within the walls could be programmed to blink on and off in sync in a pulsing pattern, mimicking the beating of a heart. The lights could be red in the left side of the heart, representing oxygenated blood, and blue in the right side of the heart, representing deoxygenated blood.

I like the removeable sections of material that many plastic 3D heart models offer, allowing users to see “into” the heart. I would include windows like this, and/or maybe just have those sections of the heart wall be fully transparent rather than partially opaque, providing a clear view into the heart. I would also include removeable sections of the wall (or septum) between the atria and between the ventricles, which combined with the use of color and light could be used specifically to illustrate the changes in blood flow that occur when a child is born with defects like that. In this way the model’s utility could be extended to include two defects: (1) an atrial communication, called an Atrial Septal Defect (ASD) and (2) a ventricular communication, called a Ventricular Septal Defect (VSD). Although there are a few different subtypes of each of these defects, the teaching model would provide a generic substrate to describe the issues with the defect in general: the mixing of deoxygenated and oxygenated blood that these holes allow. When the ASD and VSD patches are removed, the pulsating lights representing blood flow could become purple in the appropriate chamber(s) to illuminate the mixing of blue and red blood due to the hole.

There will be a stand that the heart can sit on (ultimately could be a contact or contactless charger for the lights within the walls so it can be picked up and moved around and still maintain its ability to ‘beat’).

Another feature to include would be the ability to slow and quicken the pace of the rhythm to allow families to see the motion better. Maybe a dial that can be adjusted to change pulse rate. Stretch goal: place finger on a capacitance pad on the base and see the lights change to match your own heartrate.

Week 02 - Computer-Aided Design:

• Research existing heart models and features: viewing window(s) and/or removable sections, types of light
• Begin designing the 3D model using CAD software
• Design & render using several CAD packages/tools to compare their pros & cons. Explore parametric design.
• Envision how to accommodate embedded lights within the design

I continued working with the 3D CAD file from Week 2 of an adult heart with normal anatomy (rather than a congenital heart defect) but iterated on the windows and added a VSD (ventricular septal defect).

I used the ANYCUBIC MONO X resin printer to make a prototype to test the size of the heart - both of the overall heart and of the viewing windows.

DICOM images –> 3D surface models describing the blood pool –> 3D hollow blood pool model of the normal heart, with removeable viewing windows

Print settings

Initially I used the proprietary ANYCUBIC photon workshop to slice, but ended up slicing with a different slicer called Lychee which the 3D printer lab manager suggested.

Printing

Removed from the bed:

Removing Support Material, Alcohol bath, and UV curing

Final result

User research

I have a connection with the congenital heart disease program at the local Children’s hospital in Barcelona, Sant Joan de Deu.

I was able to bring my prototype in and attend a meeting between an obstetrician, cardiologist, cardiac surgery, and members of the Sant Joan de Deu engineering & modeling team about their clinical and educational model needs.

Week 03 - Computer-Controlled Cutting:

• Evaluate cutting methods for creating prototype parts.
• Choose appropriate materials for the prototype.
• Use computer-controlled cutting tools (e.g., laser cutter) to create initial model components.
• Test and refine the cutting process.

Week 04 - Embedded Programming:

• Research & select suitable microcontrollers and embedded systems for the project.
• Develop the code to control the embedded lights and simulate blood flow through a pulsating motion.
• Test the code on a small-scale prototype.
• Iterate and optimize the programming.

Week 05 - 3D Scanning and Printing:

• Explore 3D printed materials
• 3D print prototype components for assembly.
• Validate the printed components for accuracy.
• Make adjustments to the design based on the 3D printing results.

Week 06 - Electronics Design:

• Design the electronic circuitry for controlling the embedded lights.
• Select appropriate sensors and components for data input: heart rate dial, potential touch pad to read someone’s heart rate in, isolated right or left heart mode
• Integrate the electronics into the 3D model design.

Week 07 - Computer-Aided Machining:

• Explore machining options for refining and detailing the model.
• Implement any necessary adjustments to the model based on machining requirements.
• Use computer-aided machining tools to refine the prototype.

Week 08 - Electronics Production:

• Begin production of electronic components.
• Assemble and test the electronic circuits.
• Troubleshoot and debug any issues.

Week 09 - Output Devices:

• Integrate output devices (LEDs) into the 3D model.
• Test the functionality of the output devices.
• Ensure the lights accurately represent blood flow through the right and left heart

Inspiration

• String of LEDs controlled by heartrate | Instructable link Youtube video

Week 10 - Mechanical Design & Machine Design:

• Refine the mechanical aspects of the 3D model.
• Optimize for durability and ease of assembly.
• Consider any additional mechanical components required for functionality.

Week 11 - Input Devices:

• Integrate input devices for user interaction (dial to control heart rate, finger print pad to read user’s heart reate).
• Test and refine the input devices.

Heart rate sensing

Test 1

There’s an off-the-shelf Arduino sensor called the KY-039 Heartbeat Sensor Module which uses an IR sensor to return an analog output signal. Once processed, this output translates into heart rate.

The sensor has three connections: GND, 5V, and the analog output.

On my cardiodev board I have a few analog input pins available via the headers.

I connected the IR HR sensing module but wasn’t getting a reliable read of my heartrate - even with some filtering that was built into the arduino code I found online, it was jumping around quite a bit between 30-55 BPM.

Resources: ElectroPeak | Interfacing KY-039 Heartbeat Sensor Module with Arduino

VERDICT: Keep looking, not satisfied with this HR module

Test 2

Another way to measure heart rate is with vibration detection using a piezoelectrode.

I’ve included a few resources below: Heart rate sensing w/ piezoelectrode | Instructable Interfacing with piezoelectrode demo | Interfacing with Arduino Article on using Piezoelectric sensing to detect HR| Heart Rate Detection using a Piezoelectric Ceramic Sensor: Preliminary results

VERDICT: Success! I was impressed with the level of detail the piezoelectrode picked up with just holding a fingertip to it. You could see a double peak (showing the )

Week 12 - Molding & Casting:

• Explore molding and casting options for fabricating the model
• Test materials & prototype with embedded lights to assess diffusion.

Week 13 - Networking & Communications:

• Investigate networking options for potential remote control or data exchange.
• Implement communication protocols for networking components.

Week 14 - Interface & Application Programming:

• Develop an interface for controlling the model.
• Implement application programming to enhance user interaction.

Week 15 - Wildcard Week:

• Address any unexpected issues or tasks that may have arisen during the project.
• Conduct additional testing and optimization as needed.

Week 16 - Applications & Implications:

• Evaluate potential applications and real-world implications of the project.
• Consider how the model could be used for educational purposes or medical training.

Week 17 - Invention & Intellectual Property & Income:

• Review intellectual property considerations and file for any necessary patents.
• Develop a plan for potential income generation from the project, such as licensing or commercialization.

Development Plan

Beating Heart Tutorial

A maker on YouTube named Jiri Praus developed an artistic brass wire mesh heart with beating LEDs as a 5 year anniversary present to his wife. Video here. He also includes an instructible.

Beyond practicing how to program lights in a pulsatile pattern the way I’d like to in my final project, his heart also senses the holder’s heartbeat and propagates it to the light pattern.

He uses off-the-shelf electrical components; rather than an Arduino NANO and battery charger I’ll make my own board to drive the lights. We do have a heart rate sensor module here in the lab that I’ll try to interface with.

First step in building the heart is 3D printing the 3D heart template upon which the brass wire mesh is built.

Electronics

I envision the Base and the Heart to be separate objects but the Heart needs to be able to listen to signals sent from the Base (such as the pulse rate).

Connectivity

• 2 Xiao ESP32C3 boards, one in the Base and one in the Heart
  • ESP-NOW protocol to send signal from Base to Heart

Base Assembly

• Inputs:

  • piezoelectrode (fingertip sensor for HR)
  • optional: potentiometer to dial speed of pulse

• Output:

  • will send converted signal from piezoelectrode as HR to the Heart board
  • light behind the piezoelectrode pulses to draw the user’s attention

• Power:

• ESP-NOw

  • mac address: D4:F9:8D:04:0B:44

BOM

Heart Assembly

• Inputs:

  • HR from Base assembly
  • Hall effect magnet sensor to detect if VSD patch in place

• Outputs:

  • Neopixel Ultra Skinny LED strands 5x (2 for each side of the heart, and one for the VSD )
  • Use WLED vs custom code for the heartbeat animation? wifi-enabled WLED example

• Power:

  • LED strands run on 5VDC
  • battery powered

• ESP-Now

  • Mac address: D4:F9:8D:00:F9:18

  BOM

  Component	#	Source	Price

Packaging I made a light diffusion test piece so I could see what thickness of overmolding/material corresponds to which level of diffusion of the light below it. The piece runs from .1mm thick to 6mm thick.

3D model of xiao ESP32C3 board: https://grabcad.com/library/seeed-studio-xiao-esp32-c3-1