HCC Internal Honors Competition

MoiréSkin

Ultra-Sensitive Sensor–Actuator
Visuo-Tactile Skin using Moiré Patterns

Linzhen Zhu
Liuxi Xing
Runqiu Wang
Ke Sun

Computer Science & EngineeringUniversity of Michigan

Ambient Intelligence LabAMI Lab

MoiréSkin on robot gripper

MoiréSkin sensor design

Sensingmoiré film

Actuationair chamber + pump

Imagingcamera + LEDs

Why it matters

Are you afraid of interacting with a humanoid robot?

Sensitivityto handle fragile things

+

Complianceto grip them gently

Failure case

Video: ROBOTIS · youtube.com/watch?v=1-ymnFMMVgk

Existing solution

SoTA: structured-light visuo-tactile sensors.

A robot gripper with visuo-tactile sensors
GelSight

Video: GelSight · youtube.com/watch?v=wCZZnyo7k44

Visuo-tactile sensor

Tactile → visual: a camera reads touch.

Imaging a pressed screw
GelSight

Video: GelSight · youtube.com/watch?v=wCZZnyo7k44

How they work

Why a rigid base

Structured light on a rigid base.

The problem

A rigid base limits compliance and sensitivity.

Meta · Digit 360

Exploded render of the Digit 360 fingertip sensor: a dome, a ring of lights, a lens and stacked boards in a housing

Image: Meta AI · Digit 360

Failure case · illustration

Compliancebad for robot manipulation

Sensitivitylow force cannot deform it

Visuo-tactile sensors today

Related works: sensitive, or compliant?

Our goal

MoiréSkin fills the gap.

Soft-Bubble: a bubble module with the dots printed inside its membrane for tracking

?

Background

Our insight

The answer: moiré pattern.

Moiré fringes on one soft film.

A moiré metasurface amplifies touch.

Lens · 3 mm

Lower · fluorescent

Upper · clear

μmthe film barely bends

mmthe fringes move a lot

Scroll ↕ to bring them together

Scroll ↕ to deform more · hover to move the touch

Simulation

Real sensor · light touch

[Step 1] The answer is to leverage a visual interference phenomenon, called the moiré pattern. It is generated when two gratings of fine parallel lines overlap at a small angle. [Step 2] We put them on the two faces of one soft film. Where they overlap, moiré fringes appear: each fringe is a row of points where the lines cross. (Scroll to bring the two gratings together.) [Step 3] Now touch the film. The dent squeezes the upper face and stretches the lower one: a tiny deformation, just one percent. Like nearly closed scissors, the two sets of lines barely move, but their crossing points slide a long way: the fringes there turn by about five degrees. So this film is a metasurface that amplifies touch. (Scroll to deform it more; hover to touch another place.) [Step 4] And here is our real sensor. A tiny yellow bean, lighter than one gram, is enough to deform these super-sensitive fringes.

Hardware

Three modules in one cell.

Our grating film under a microscope: fine parallel lines — Our film under a microscope

Coverclear TPU

Upper grating330 μm

Substratesoft silicone

Lower gratingfluorescent

Air chamber

Pumpone controller

Camera1080p · 160°

LED ringfaces down · blue

Diffuse reflector

Fabrication

Two gratings → one soft film.

Fluorescent lower grating
Clear upper grating
One soft film

No cleanroom · reusable molds

Nine-step fabrication of the dual-grating film: fluorescent lower grating printed, cured and lifted off; clear upper grating spin-coated and imprinted; final drying

Design

Clear fringes, clear skin, low cost.

Glowing fluorescent fringes seen by the internal camera

Fluorescent grating

keeps high contrast

See through

sees before touch

<$2per cell

No cleanroom

≈ $50 for the whole system

How it works

Challenge 1Sensitivity vs spatial resolution.

Force
sensitivitythe lightest touch
a fingertip feels

Spatial
resolutionhow finely it tells
where the touch is

Videos: Nui Malama, cottonbro studio · Pexels

the angle between
the two gratings

Scroll ↕ to change the angle · hover to press

Simulation

Real sensor · touch

Sensing

How we detect force + position.

Sensing

Most sensitive reported to date.

0mNnormal force

≈ a sticky note’s weight

0mmposition

≈ a hair’s width

Actuation

Why do we need actuation?

A gripper already moves. Why actuate the skin?

A compliant layer · right at the contact
Regulates the contact force · in a closed loop
Compensates for low precision · even on a toy arm

Actuation enables dexterity for even a toy arm.

MoiréSkin
Failure case · illustration
MoiréSkin · sensing + actuation

Toy-grade, low-precision arm

1Grasp the cup
2Water pours in
3Feels the weight, inflates
4Without feedback, it would fall
5Holds steady, sets it down

How it works

Challenge 2Actuation needs to know the internal pressure.

Challenge 3Outside air pressure causes drift.

Fringe rotation angle → internal pressure.

Fringes turn without any force.

Pump until centre and rim line up.

Chamber: 0.0 hPa
Centre turns: 0.0°

Scroll ↕ to pump air

Outside air: 1013.2 hPa
Centre turns: 0.0°
Rim turns: 0.0°

Centre vs rim: 0.00°
Pump: Zero ✓

Simulation

Real sensor · inflation

Real sensor · pumping

Real sensor · zeroed ✓

[Step 1] So our second challenge: reading the internal pressure for actuation. We read it from the fringes themselves, with no external pressure sensor: when the skin inflates, its centre is stretched, so the fringes there turn, and their rotation angle tells us the pressure. (Scroll to pump.) [Step 2] (The real sensor takes the simulation's place.) Here is the real sensor as its internal pressure changes. [Step 3] Our third challenge is drift. The chamber is sealed, so as the outside air pressure changes by 10 to 20 hectopascals a day, the fringes turn without any force. So how do we find the zero state automatically? [Step 4] Whenever the film bulges or sags, the centre and rim fringes turn in opposite directions. So we pump until they line up: the film is flat, and that is zero, found without any extra sensor. [Step 5] (The real sensor takes the simulation's place: the pump straightens the fringes.) Here is the real sensor during zero-state calibration.

Sense + actuate

Case study: softness classification.

0%10-shot · 7 materials

92.7%5-shot

≈ soft tofu≈ skin softer than
a marshmallow

Young’s modulus · 8.7–21.7 kPa

Real sensor

Sense + actuate

Case study: shear force sensing.

0gmean error · unseen session

4.75gRMSE

0–300mLwater poured in

Cup held against MoiréSkin in a bench vise — Real setup

Sense + actuate

One pre-trained backbone, two new skills.

Data collection kit

Humans teach, robots learn.

Gripper after UMI · Chi et al., RSS 2024 · umi-gripper.github.io

UMI-style handheld gripper

UMI by Stanford University Columbia Engineering Toyota Research Institute

Senses tactile contactfrom fringe changes

Sees the berrythrough the skin

Takeaways

Ultra-sensitive · 3.78 mN
Compliant · grips fragile things gently
Actuating · feels its own pressure
See-through · sees before touch

Computer Science & EngineeringUniversity of Michigan

Ambient Intelligence LabAMI Lab

Project page

ACM MobiCom 2026 · Austin, TX

MoiréSkin

One of the world’s most sensitive tactile sensors and actuators.

Linzhen Zhu
Liuxi Xing
Runqiu Wang
Ke Sun

Our vision

A skin that feels and acts,
on every future robot.

Thank you.

Computer Science & EngineeringUniversity of Michigan

Ambient Intelligence LabAMI Lab

Project page

MoiréSkin

Are you afraid of interacting with a humanoid robot?

SoTA: structured-light visuo-tactile sensors.

Tactile → visual: a camera reads touch.

Structured light on a rigid base.

A rigid base limits compliance and sensitivity.

Related works: sensitive, or compliant?

MoiréSkin fills the gap.

The answer: moiré pattern.

Moiré fringes on one soft film.

A moiré metasurface amplifies touch.

Three modules in one cell.

Two gratings → one soft film.

Clear fringes, clear skin, low cost.

Fluorescent grating

See through

No cleanroom

Challenge 1Sensitivity vs spatial resolution.

How we detect force + position.

Most sensitive reported to date.

Why do we need actuation?

Challenge 2Actuation needs to know the internal pressure.

Challenge 3Outside air pressure causes drift.

Case study: softness classification.

Case study: shear force sensing.

One pre-trained backbone, two new skills.

Humans teach, robots learn.

MoiréSkin

A skin that feels and acts,on every future robot.

A skin that feels and acts,
on every future robot.