Matter Stack · tangible display · design published, build pending
Matter you can grasp, sound that moves, light that explains.
A three-layer tangible display. Ferrofluid over an addressable electromagnet grid forms persistent, touchable terrain; a phased ultrasonic field flies a millimetre bead through the air above it and projects pressure points onto the user's skin; a projector or AR view paints texture, labels, and color onto both. Each layer does exactly what its physics does best.
Ultrasound is a pressure phenomenon; ferrofluid responds only to magnetic fields. The two force media coexist in one volume without interfering — that single observation is what makes the display possible. The stack is ordered by mass and timescale: terrain is the slow voice (0.2–1 s), the levitated bead is the fast voice (metres per second), light is the palette.
Ferrofluid terrain
A sealed cell of ferrofluid over a 4×4 (later 8×8) electromagnet grid. Persistent, graspable shape that stays put when held. Flyback diodes on every coil are mandatory.
16 → 64 coils · duty cap 60–70%
TinyLev → MATD
A TinyLev-class standing-wave levitator first; the upgrade path replaces it with a per-transducer phased array that steers the bead at up to 8.75 m/s and delivers mid-air haptics.
72× 40 kHz · shared with MTS Build Sheet 002
Projected detail
Projector, phone AR, or eye-worn display carrying texture, labels, and text at effectively unlimited resolution. The bead is a trajectory-known fiducial that anchors the coordinate frame.
registration via the bead · depth camera later
The ladder
Gates S1–S5 and their kill criteria are in the checklist, written before any hardware is bought. Do the stages in order — each reuses the skills and most of the hardware of the one before it; attempting the phased array first is the most common way this project fails for a first-time builder.
Documents
Complete Design & Build Compendium
The combined document: Parts I–VII, from the original build guide to the full parts list with vendors. Start here.
Build Guide — Concept, Build, Holodeck Roadmap
Part I. The concept, the TinyLev acoustic layer, the ferrofluid magnetic layer, integration, and a candid analysis of what does and does not scale toward a holodeck.
Illustrated Build Manual
Part II. Step-by-step 4×4 build, the 4×4 → 8×8 upgrade, and the MATD phased-array path, with diagrams. Transducer polarity testing is the highest-leverage hour of the build.
Art & Expressive-Medium Addendum
Part III. The 8×8 sound-reactive instrument: a two-speed voice, room-sound mapping, micro-theater, and the roadmap to a museum-grade installation. Temporal composition, not spatial resolution.
Choreography Engine — Software Specification
Part IV. Data formats, scene-file JSON schema, and the serial protocol to the two Arduinos. Host computes, controllers actuate; one clock, one frame; fail safe by default.
Execution Checklist & Gate Criteria
Stages 1–5: purchase lists, build order, actual-vs-predicted tables, gates S1–S5. Same rules as the MTS Phase 0 checklist — print it, fill it in ink.
Status
Safety, in one line each
Flyback diodes on every coil, counted before first power-up. Ferrofluid stains permanently — keep it sealed, work gloved over sheeting. 40 kHz ultrasound is intense at close range: fingers out of the near field, exposure in seconds, pets out of the room.
Authorship & method
This research is drafted in human-AI collaboration: analyses are AI-drafted under the owner's direction, then re-derived, red-teamed, and adopted or rejected by the owner. All decisions, inventions, and commits are Christopher Brotherton's; commits credit AI drafting via Co-Authored-By trailers. The dated commit history is the record of human contribution.
Technical critique is welcome and useful — open an issue. Errors that survive review get corrected in a dated commit.