Precision Mechatronics: Atomic Force Microscopy (AFM)

We develop atomic force microscopes that measure more surface area, capture faster nanoscale dynamics, and access features that conventional probes cannot easily reach. Our goal is high-throughput imaging that preserves the precision and sensitivity needed for semiconductor inspection and fundamental materials research.

Our work connects active cantilever design and nanofabrication with large-range nanopositioning, fast imaging, multi-probe alignment, and feedback control. Current efforts include wafer-scale inspection, specialized probes for complex geometries, thermal-actuator compensation, and instruments for cryogenic and quantum-material studies. Hands-on AFM platforms and interactive simulations bring these ideas into mechatronics education.

Research Image Gallery

Two-by-two arrangement of Bruker Dimension Icon, Nanosurf Alphacen 300 Flex, Park Systems industrial AFM and nano analytik active-probe wafer inspection photographs.

AFM Instruments

Commercial AFM instruments for materials research and wafer inspection.

Complete AFM instrument photograph and subsystem diagram covering the nanopositioner, sensor and actuator, probe, controller and data logging.

AFM System Overview

Probe, scanner, sensing and feedback work together to map surface topography.

Diagram of AFM cantilever geometry and optical, interferometric, evanescent, piezoelectric, and piezoresistive sensing methods.

AFM Sensing Transducers

Optical and integrated transducers measure deflection of the AFM cantilever.

Complete contact, dynamic and jumping mode diagram with all original mode labels and the course peak-force-tapping annotation.

AFM Imaging Modes

Contact, dynamic and jumping modes measure probe–surface interactions.

Complete AFM analysis pipeline with time scale, data size, data type and automation level, paired with the multidimensional data-cube and pixel-parameter diagrams.

AFM Data and Hyper-Pixels

Multichannel hyper-pixels preserve local topography and material responses.

Active Probe Atomic Force Microscopy

A practical guide to active-probe AFM design and precision instrumentation.

Four active cantilevers for parallel large-area wafer inspection (JoVE 2023).

Parallel Active-Probe Inspection

Four active cantilevers perform parallel wafer inspection (JoVE, 2023).

Four-Probe EUV-Mask Panorama

Four-probe EUV-mask panorama and patterned traces shown together.

Animation demonstrating parallel active-probe AFM inspection of an EUV mask.

EUV-Mask Inspection

Animated demonstration of parallel active-probe inspection of an EUV mask.

Active-Probe Gantry

An active-probe gantry integrates sample scanning, microscope motion and tilt.

Microscope image after AlN etching in the active-probe fabrication process.

AlN Probe Fabrication

Microscope views of active-probe structures following the AlN etching step.

Microscope images of custom AFM test structures: canyon, L-bar, grid, and vernier patterns.

Nanofabricated Test Patterns

Nanofabricated canyon, L-bar, grid and vernier patterns for AFM testing.

Animated AFM observation of calcite etching, acquired at 20 frames per second and shown at four-times playback speed.

Calcite Etching at 20 FPS

Dynamic calcite etching captured at 20 frames/s and shown at 4× playback.

High-Speed AFM Instrument

A high-speed AFM instrument designed for rapid scanning over local areas.

Ten-layer stacked scanner for high-bandwidth motion

Stacked High-Bandwidth Scanner

Ten stacked scanner layers provide actuation for high-bandwidth motion.

Lumped mass-spring-damper model of a ten-layer stacked nanopositioner, including layer coupling and payload mass.

Ten-Layer Scanner Model

A lumped mechanical model describes a ten-layer stacked nanopositioner.

20 kHz Scanner Tracking

Measured scanner response tracks a triangular waveform at 20 kHz.

AFM image distortion before and after scanner-control correction

Image Distortion Correction

AFM images show distortion before and after scanner-control correction.

Cryogenic scattering-type near-field optical microscope

Cryogenic Near-Field Microscopy

Cryogenic scattering-type microscopy probes nanoscale optical responses.

Infrared Optical Integration

An integrated infrared optical path supports near-field spectroscopy.

AFM and near-field infrared imaging of domain walls in stacked graphene

Graphene Domain-Wall Imaging

AFM and near-field infrared images reveal domain walls in stacked graphene.

Quantum Twisting Microscopy

Sample rotation changes the twist angle at the probe–sample junction.

QTM Instrument Platform

An implemented mechanical platform supports quantum twisting microscopy.

Rotation-Center Alignment

Optical microscopy aligns the rotation center with a selected sample flake.

Music-Wire Scanner

Hardware and mechanical design of a dual-actuated music-wire scanner.

Multi-layer stacked piezo scanner concept

Stacked Piezoelectric Motion

A multilayer stacked piezoelectric scanner combines motion across layers.

Dual piezoelectric inputs drive tangential motion and modulate normal force.

Variable-Friction Positioner

Two piezoelectric inputs regulate tangential motion and normal force.

The measured backward-to-forward displacement ratio falls from 59.5% to 15.3% at 30% modulation duty cycle.

Reduced Backward Slip

Backward/forward displacement falls from 59.5% to 15.3% at 30% duty.

CAD model and assembled dual-probe AFM with coordinated height and tilt positioning.

Dual-Probe Tilt Testbed

A dual-probe AFM testbed coordinates vertical positioning and sample tilt.

Flexure geometry and finite-element displacement analysis.

Tilt-Stage Flexure Design

Flexure geometry is evaluated through finite-element displacement analysis.

Self-Sensing Active Probes

Piezoresistive sensing and thermal actuation are integrated in one probe.

Design of adjacent contact and dynamic probes with electrical access.

Contact–Dynamic Probe Pair

Adjacent contact and dynamic probes provide separate electrical access.

Diagram of piezoelectric base excitation, electrothermal, photothermal, magnetic, electrostatic, and integrated piezoelectric actuation of AFM cantilevers.

AFM Probe Actuation

Mechanical, thermal, optical, magnetic and electrical probe actuation.

Reference fabrication sequence for piezoelectric MEMS probes.

MEMS Fabrication Process

A reference fabrication process produces piezoelectric MEMS probe structures.

Microscope image after oxide etching in the active-probe fabrication process.

Oxide-Etched Probe Structures

Microscope views of active-probe structures after the oxide etching step.

Optical characterization of active cantilevers with independent interferometric displacement readout.

Optical Probe Characterization

Interferometric measurements characterize active-cantilever displacement.

Real-Time and FPGA Software

LabVIEW real-time and FPGA software coordinate instrument operation.

Bandwidth-based repetitive control for a multi-actuator scanner.

Multi-Actuator Repetitive Control

Bandwidth-based repetitive control coordinates multiple motion actuators.

Disturbance-observer architecture for scanner nonlinearity compensation.

Disturbance-Observer Control

A disturbance observer compensates nonlinear behavior in the scanner.

Clipped square-root preprocessing counteracts the quadratic voltage-to-power relation; an alternative estimation path is shown.

Power-Domain Compensation

Square-root commands compensate the quadratic voltage-to-power relation.

At matched command settings, compensation reduces the sampled second-harmonic resonance peak by 25.1 dB.

Measured Harmonic Attenuation

The second-harmonic peak decreases by 25.1 dB at matched commands.

Shared height and relative tilt errors drive coordinated actuation.

Coordinated Height and Tilt

Shared height and relative tilt errors drive coordinated probe actuation.

3D printer converted into a macroscopic AFM with ruler cantilever, strain gauge and measured surface data.

3D-Printer AFM

An Ender 3 printer uses force feedback to map the shape of a surface.

Custom AFM scanner with dimensioned flexure design, finite-element simulation, stacked piezo-buzzer actuation and fabricated prototype.

Custom Scanner Design

Flexure simulations guide the design of a stacked piezo-buzzer scanner.

Student-acquired AFM topography with original spatial and height scales, shown on a borderless landscape frame.

Student AFM Topography

Surface topography acquired by students using the educational AFM platform.

CAD assembly of an educational atomic force microscope and its mechanical and electronic subsystems.

Educational AFM Platform

An educational AFM integrates mechanics, electronics and measurement.

AFM SMILER

An interactive extended-reality toolkit supports scale-model AFM learning.

LabVIEW Frequency Sweep

LabVIEW motor frequency sweeps measure amplitude and phase response.

Special-Feature Imaging

We develop specialized AFM probes and sensing methods for complex features and material properties.

Objective: Develop measurement capabilities for high-aspect-ratio features and subsurface electrical contrast.
Significance: Access geometric and electrical information beyond conventional topographic imaging.
Result: Established a Nanosurf DriveAFM platform with LabVIEW control and specialized probe capabilities. Scanning microwave microscopy electronics and hardware integration are in development.

Active-Probe Wafer Inspection

Miniaturized active cantilevers integrate actuation and sensing at the probe, providing a route to parallel wafer-scale measurement and complementary measurements in a single pass.

Objective: Develop custom active-probe arrays and the positioning, readout, and characterization tools needed for large-area, multimodal AFM.
Significance: Parallel probes expand the inspected area while on-probe actuation reduces dependence on the bandwidth of a shared scanner.
Result: Prior work demonstrated four-probe parallel inspection and a 500 µm × 125 µm EUV-mask panorama. Current UT work has established probe designs, on-campus fabrication steps, a gantry, and characterization hardware; multimodal imaging integration remains ongoing.

JoVE: Instrument Overview

JoVE: Wafer Imaging Demonstration

Published prior work: four active cantilevers for parallel wafer inspection, Journal of Visualized Experiments, 196, e65210 (2023).

Double-Probe Tilt Compensation and Imaging

Parallel AFM needs more than additional probes: each probe must engage the surface while shared motion compensates for sample tilt. Our dual-probe testbed coordinates coarse angular alignment, fine tilt actuation and vertical positioning using the two cantilever amplitude signals.

Objective: Bring spatially separated active probes into stable engagement and maintain their amplitude setpoints during scanning.
Significance: Automatic tilt and height coordination addresses a practical obstacle to scaling AFM from one probe to parallel inspection.
Result: Demonstrated dual-probe engagement and amplitude regulation with coordinated tilt and height compensation.

Representative study: “Sample Tilt Control for Atomic Force Microscopes with Multiple Parallel Active Cantilevers,” 2026 American Control Conference.

Thermal Probe Nonlinearity

An electrothermal active cantilever uses the same heater for mean bending and oscillatory excitation. We characterize the resulting nonlinear coupling and implement power-domain compensation and probe feedback to control these motions more independently.

Objective: Compensate the quadratic voltage-to-power relation while regulating active-probe position and resonance behavior.
Significance: Predictable on-probe actuation supports compact, faster AFM and provides a building block for parallel-probe systems.
Result: Bench measurements show a 25.1 dB reduction in the sampled second-harmonic resonance peak at matched commands. Separate active-feedback tests reduce apparent Q from 423 to 235.

Quantum Twisting Microscopy (QTM)

In collaboration with UT Austin physics researchers, we build precision probe and sample positioning systems for studying electronic coupling in two-dimensional materials as their relative twist angle changes.

Objective: Integrate independent probe and sample stages, rotation-center alignment, tilt compensation, and functionalized active probes.
Significance: A rotating tunnel junction reveals how twist angle affects interactions between two-dimensional layers.
Result: The mechanical platform and probe-functionalization workflow have been implemented, with microscopy-based alignment and ongoing work toward low-temperature probe characterization.

Sponsors and Collaborators

Sponsors: Samsung Electronics · Department of Energy · UT ME Startup Funds

Collaborators: Prof. Ken Shih · Prof. Leo Jia · Prof. Ivo Rangelow

Back to Research | Explore Advanced Mechatronics II

MINIMAX Lab

Precision Mechatronics: Atomic Force Microscopy (AFM)

Research Image Gallery

Special-Feature Imaging

Nanosurf DriveAFM Platform

High-Aspect-Ratio Reference Tip

Microwave Readout Electronics

Active-Probe Wafer Inspection

JoVE: Instrument Overview

JoVE: Wafer Imaging Demonstration

Double-Probe Tilt Compensation and Imaging

Dual-Probe Tilt Testbed

AlN Probe Fabrication

Dual-Probe Engagement

Thermal Probe Nonlinearity

Electrothermal Probe Coupling

Interferometric Characterization

Measured Harmonic Attenuation

Quantum Twisting Microscopy (QTM)

Twistronics

QTM Instrument Platform

FIB Probe Functionalization

Sponsors and Collaborators