Diameter spans tens of nanometers to hundreds of micrometers; transient FEM predicts curvature to a fraction of a turn.
2D fabrication → 3D function
Structures that assemble themselves.
Strain-induced self-rolled-up membrane (S‑RuM) technology transforms lithographically defined thin films into compact three-dimensional architectures through spontaneous strain relaxation.
10–100×smaller RF inductor footprint
>20 GHzdemonstrated RF operation
20×faster neurite growth in tubes
The platform
Precision mechanics, built into the material stack
An oppositely strained bilayer is patterned using planar processing. Selective removal of a sacrificial layer releases the membrane; competing tensile and compressive stresses generate a bending moment that rolls the membrane into a predetermined 3D form.
- 01
Build in strain
Deposit tensile and compressive nanoscale layers above a selectively removable sacrificial layer.
- 02
Define the architecture
Lithography sets the rolling direction, membrane length, device pattern, and number of turns.
- 03
Release and transform
Undercut frees the membrane. Stored elastic energy drives spontaneous 2D-to-3D assembly.
- 04
Integrate function
Semiconductors, dielectrics, metals, 2D materials, and electrodes can be incorporated before rolling.
Wafer-scale 2D patterning creates complex 3D systems in parallel without serial assembly.
Functional materials and devices are positioned on curved surfaces and within tubular channels.
Application landscape
One platform, four physical domains
Extreme miniaturization of RF and power passives
Inductors, transformers, capacitors, and L–C networks
Rolling long planar conductors into air-core microtubes creates high inductance density in a fraction of the footprint. Multiple device elements can be defined in a shared lithography flow and interconnected before rolling.
- Inductance density above 3 μH/mm²
- Capacitance density up to 371 pF/mm²
- Near-unity transformer coupling demonstrated
- mT-level on-chip magnetic induction with ferrofluid cores
Out-of-plane optical routing
Vertical resonators and 3D photonic coupling
Curved dielectric membranes form compact vertical microresonators and couplers that can be monolithically integrated with planar waveguides. Geometry provides a direct lever for wavelength tuning, axial confinement, and multichannel coupling.
- Vertical microring resonators
- Monolithic coupling to ridge waveguides
- Curvature-tunable quantum-well emission
Planar waveguideVertical microresonatorLight is redirected into a compact third dimension.
Lab-in-a-Tube
Guiding, accelerating, and manipulating biological systems
Tunable cylindrical channels combine confinement with integrated electrodes and optical access. Demonstrations include directed neurite growth, low-voltage electrophoretic manipulation, and on-chip DNA storage.
- Neurite growth directed through tube arrays
- Growth rates up to 20× faster than planar controls
- Electrostatic trapping of DNA molecules
Reconfigurable curvature
Electrostatically actuated and self-correcting membranes
Thin rolled membranes can be driven between curvature states. Electron-beam charging has demonstrated continuous deflection, tube closure, and correction of incompletely rolled structures.
- Micrometer-scale deflection
- Open-to-closed tubular motion
- Array-level self-healing potential
Research evidence
From mechanics to integrated systems
Selected peer-reviewed results spanning the platform’s formation, modeling, and functional demonstrations.
2022 · ACS Applied Materials & Interfaces
Self-rolled-up aluminum nitride-based 3D architectures enabled by record-high differential stress
Extends the platform to high-stress AlN membranes for tightly curved 3D architectures.
2020 · Advanced Functional MaterialsMonolithic heterogeneous integration of 3D radio-frequency L–C elements
Combines inductive and capacitive elements in a compact rolled architecture.
2020 · Science AdvancesMonolithic mTesla-level magnetic induction by self-rolled-up membrane technology
Demonstrates strong on-chip magnetic fields from geometrically transformed conductors.
2018 · Nature ElectronicsThree-dimensional radio-frequency transformers based on S-RuM
Compact transformers with strong coupling and favorable turns-ratio scaling.
2022 · Microsystems & NanoengineeringSelf-assembled microtubular electrodes for low-voltage electrophoretic manipulation
Curved electrodes concentrate electric fields for on-chip manipulation of charged particles and macromolecules.
2018 · ACS Applied Materials & InterfacesAligning synthetic hippocampal neural circuits via self-rolled-up silicon nitride microtube arrays
Ordered tubular guidance structures align neuronal processes and organize synthetic hippocampal circuits.
2014 · ACS NanoToward intelligent synthetic neural circuits: directing and accelerating neuron cell growth
Self-rolled-up silicon nitride microtube arrays direct cortical neurites and accelerate their growth relative to planar substrates.
2018 · Applied Physics LettersPassive wavelength tuning and multichannel photonic coupling
Vertically integrated microresonators couple multiple optical channels on-chip.
2016 · Applied Physics LettersEnhanced axial confinement in a monolithically integrated self-rolled-up SiNx vertical microring photonic coupler
A high-index strip creates stronger axial confinement, wider mode spacing, and single-mode operation in the telecommunications C- and S-bands.
2015 · Applied Physics LettersMonolithically integrated self-rolled-up microtube-based vertical coupler for 3D photonic integration
A tubular resonator integrated above a planar ridge waveguide enables strong vertical optical coupling using planar-compatible fabrication.
2010 · Applied Physics LettersTuning photoluminescence with curvature in rolled-up GaAs quantum-well microtubes
Curvature and patterned openings tune emission while enhancing photoluminescence intensity and light extraction.
2014 · Nano LettersPrecision structural engineering guided by transient quasi-static FEM
Predicts and controls complex rolling trajectories with high precision.
For a broader bibliography, see the S‑RuM research page.
Patent Portfolio II
Protected S‑RuM inventions
Nine patent families cover compact RF and power passives, wireless structures, magnetic components, DNA storage, and post-roll performance enhancement.
Rolled-up transformer structure for an RFIC
Application 14/051,208 · Issued 2015
Rolled-up transmission line structure for an RFIC
Application 14/051,192 · Issued 2015
Rolled-up inductor structure for an RFIC
Application 14/051,188 · Issued 2015
Tubular resonant filter
Application 15/092,979 · Issued 2018
Rolled-up power inductor and arrays
Application 15/704,262 · Issued 2019
Helical antenna and performance modulation
Application 15/408,893 · Issued 2019
Rolled-up magnetic component for on-chip applications
Patent 11/031,456 · Issued 2021
On-chip nanoscale storage using chimeric DNA
Application 16/593,450 · Pending
Electroplating to enhance rolled-up passive components
Application 17/503,603 · Pending
Research & collaboration
Build in two dimensions.
Think in three.
Professor Xiuling Li
Electrical & Computer Engineering
The University of Texas at Austin