One small object, finished — and a portfolio a stranger can understand
Human Biology for the Medical Maker
Why this chapter exists
A finished, humble, well-documented project beats an ambitious unfinished one every time.
The capstone runs over weeks 27 to 30
Choose one route
Route
What it is
Key partner
Training model
An articulated anatomical model or simulation fixture — the elbow model is the default
Simulation educator
Assistive technology prototype
A tabletop mock-up of an adaptation; any user trial follows the team's review process
Occupational therapist and the intended user
Software or instrumented tool
Fictional data, or a battery-powered sensor model giving feedback; no connection to a person or live systems
Educator, plus information governance if data arise
The making methods are open — card, wood, metal, fabric, silicone, acrylic, printed and machined parts, electronics, code. Method comes after objective.
No partner yet?
Complete a clearly labelled independent demonstration project
Use the elbow model with a fictional brief
Finish all the technical work
Record sponsor-dependent criteria as pending
"Items 4, 7, and 9 await educator review" beats a project whose review was imagined.
Week 27: confirm the brief
Settle it in writing before you cut anything
The brief you will build against
Need and scope
Learners must distinguish a force source from a tendon's transmission
Manually operated tabletop aid; reset by hand
Not attached to a person, not load bearing, not every structure
Initial success criteria
Movement is visible
Labels distinguish generation from transmission
An unfamiliar learner can attempt the questions
Reset without tools
These are learning-project criteria to discuss with an educator — not device specifications.
Confirm in writing before you cut anything
Item
Must be settled
The need
Stated without a solution, confirmed by the sponsor
The scope
Including what it is not
Relevant anatomy
Which structures at what simplification
Reviewers
Named people, by role
Requirements
Three to five, measurable, criteria agreed now
Contact category
For this project: no body contact
Cleaning, storage, ownership
Who, how, where — and who owns it after handover
What finished means
Specific deliverables and a date
Compare two concepts, and record why
Criterion
A: open card and cord
B: enclosed fabricated mechanism
Comment
Force path visible
Strong
Weak
Decisive
Build time and iteration cost
Hours; trivial
Days; high
The first design will be wrong
Durability and cleanability
Low; poor
High; better
Not yet requirements
Perceived quality
Low
High
Irrelevant — beware its pull
Risk of teaching the wrong thing
Lower
Higher — mechanism hidden
Decisive
Choice — Concept A, because the enclosed version hides exactly the relationship being taught.
Weeks 28 and 29: build the first version cheaply
Begin with card, even though you have a workshop
Begin with card
You have machine tools, a laser cutter, a printer, a sewing machine, an electronics bench
Do not use them yet
The first question is whether the relationship can be understood
Change the layout five times before investing in polish
Materials: two card strips about 200 by 35 mm, a paper fastener, non-elastic cord, a smooth guide loop, labels.
Build sequence
Join two segments at a pivot about 20 mm from the ends; round sharp corners
Upper arm vertical, forearm horizontal; label both as schematic
Cord attached about 40 mm from the pivot — reinforce the card there
Guide loop about 80 mm above the pivot; pull gently to bend
Operate slowly; stop before collision; no weights
Label the mechanism; reset by hand; mark V0.1 and the date
Label the mechanism — the most important step
Element
Label
Free pull end
External force input representing muscle action
The cord
Tendon representation — transmits force, does not generate it
V0.1 — tabletop education prototype. Schematic, not to scale
If the educator wants actual tendon attachments, that is a different project, not an adjustment.
Troubleshooting: ask what changed
Observation
Possible explanation
Next check
Strip barely moves
Pivot friction, or cord line nearly through the pivot
Move by hand; examine the moment arm
Card tears at the attachment
Load concentrated at a point
Reinforce and distribute
Cord slips out of the guide
Guide does not retain it through the travel
Revise; re-test from the beginning
Learner calls the cord a muscle
Source and transmitter visually merged
Separate them; ask a different learner
Works for you, not the educator
You know things the object does not communicate
Find out what you knew
Change one important feature at a time — and record unexpected effects too.
Run a short bench review
"V0.1 completed [number] of [planned] cycles under [conditions]. We observed [facts]. This supports [a narrow conclusion]. It does not establish [what it does not]. We still need [the next evidence]."
Never fill in a successful result before doing the work.
Review the learning claim
1. Educator review of the anatomy
Anatomy, labels, and limitations
Record corrections verbatim
"Could still be misread" is the finding
2. Learner trial
Prediction before; explanation after
Every prompt, verbatim; confusions in their words
Did they name a limitation? "Learner 1", not a name
A partial result is a result. Revise, then check with a different learner.
Decide when better fabrication is justified
Move beyond card for a reason
Reasons, and a non-reason
Reasons to move beyond card
A recorded failure under the intended handling
Clearer geometry is needed — and you can say which
An agreed requirement for a stable assembly
A cleaning requirement card cannot meet
The trial showed something card cannot make visible
Not a reason
"It would look more professional"
A polished object can teach worse by hiding its mechanism
Choose a method for each element
Element
Candidate methods
Watch for
Segments
Laser-cut acrylic or plywood; machined aluminium; printed; moulded for many copies
Low-stretch braided cord; stainless cable with ferrules
Sudden release; sharp cable ends
Labels and cues
Laser-engraved or painted text; tactile features
Wear, cleaning, letter size for the viewing distance
Optional electronics
Angle sensor with LED bar or display, battery powered
Must not supply force or hide the mechanism
A plausible version one
Laser-cut acrylic segments with engraved labels, a turned acetal bush on a stainless pin, a sewn red fabric "muscle" separate from a white braided cord — and no electronics.
Every choice carries a sentence saying why. A material change is a new version — repeat every affected check.
Week 30: review, revise, hand over
Someone else must be able to pick it up
Assemble the handover
Item
Content
Need, objective, scope
No solution in the need; observable objective; what it is not for
Drawings and design files
CAD; laser, CNC, and print files; patterns; moulds; schematics; firmware — with revisions
Bill of materials
Every part with grade, supplier, quantity
Assembly and process notes
Order of operations; settings, cures, stitches, firmware version
Version history, requirements, tests
What changed and why; criteria with dates; failures included
Feedback log, limitations
Prompts recorded separately; every deliberate omission
Status, next decision
The honest paragraph; who decides what happens next
Hand it to someone who has not seen the project. Every gap they hit is a documentation defect.
The status statement
"Tabletop demonstration prototype, V1.0. It shows a selected bending motion and a simplified force-transmission relationship. It omits forearm rotation, exact attachment anatomy, active extension, and all living tissue behaviour. Shared-classroom acceptance remains pending infection prevention review."
Update it when the evidence changes — not when your confidence changes.
The five-minute explanation
The need, and who said so
The relevant anatomy, correctly
The design decision and the rejected alternative, with the reason
The evidence, including at least one failure
At least three limitations
The next decision, and who makes it
Then ask: "What's the biggest unresolved question here?"
Exit criteria
Sponsor confirms the need is addressed — or it is recorded as pending
All agreed tests recorded, including failures
Someone else reconstructs the design from your documentation
Five-minute explanation; three limitations unprompted
No prototype described as approved for patient use
What this chapter does not establish
A completed capstone is not a qualification
A sponsor's confirmation is not approval to deploy
Bench results characterise your object under your conditions
Finishing does not mean you may work unsupervised
The honest version is the valuable one
Next — Next steps, specialisms, and finding a place to contribute.