Biomechatronics: Capsule Robots

We develop ingestible capsule robots that sense, move, and interact with the gastrointestinal environment. Our goal is to extend capsule-based examination beyond passive imaging toward controlled navigation, local mechanical sensing, and sustained monitoring of gastrointestinal function.

Our research combines magnetic actuation with miniature transducers, wireless electronics, soft test phantoms, and model-based estimation and control. Prior work on long-residence capsule systems and distributed sensors informs current efforts in magnetic navigation, IMU-based motion coherence, palpation, and compact surrogate models for real-time control.

Research Image Gallery

Battery and printed circuit board share the capsule enclosure.

Capsule Electronics

A battery and printed circuit board share the compact enclosure of the capsule robot.

Flexible Sensor Prototype

Miniature flexible sensor prototypes combine sensing elements with wired connections.

Porcine measurements map Bluetooth signal strength at different locations.

Wireless Link Testing

Measurements in a porcine model map Bluetooth signal strength at different locations.

A size-000 capsule illustrates the packaging constraints of ingestible electronics.

Capsule Scale

A size-000 capsule illustrates the space available for miniature ingestible electronics.

Top and oblique views of a capsule rolling under an external rotating magnet.

Coated Capsule Rolling

Top and oblique views show capsule rolling driven by an external rotating magnet.

Camera and inertial feedback connect the capsule testbed to the pitch controller.

Integrated Control Testbed

Camera and inertial feedback connect the capsule testbed to magnetic pitch control.

A tether links the gastric station with miniaturized sensing satellites.

Satellite Sensor Assembly

A tether connects the gastric base station to miniature satellites for distributed sensing.

Internal magnets and four external coils provide controlled pitch actuation.

Capsule and Coil Design

Internal magnets and four external coils provide controlled actuation of capsule pitch.

Patterned magnetic domains provide directional actuation while preserving the cavity.

Anisotropic Coating Design

Patterned magnetic domains guide capsule motion while preserving its internal cavity.

Magnetic Coating Fabrication

A coil at the print nozzle controls magnetic polarity during composite deposition.

Capsule Electronics

The capsule enclosure holds a battery and circuit board for miniature onboard electronics.

Three-dimensional circuit layout fits actuator electronics into a capsule envelope.

Pump Driver Packaging

A three-dimensional circuit layout fits the pump driver within a capsule-sized enclosure.

Rolling and turning tests examine capsule motion on wet, textured silicone.

Wet Gastric Phantom

Rolling and turning tests examine how capsules move across wet, textured silicone.

Distributed actuation deforms a silicone substrate for motility-inspired sensing tests.

Vertical Motion Phantom

Controlled vertical motion of a soft phantom validates sensing with distributed IMUs.

IMUs and ArUco markers measure motion on a deformable viscoelastic surface.

In-Plane Motion Phantom

IMUs and optical markers track in-plane motion across a deformable phantom surface.

A hemispherical dielectric elastomer models localized GI-wall motion.

Soft Phantom Actuator

A hemispherical dielectric elastomer models localized gastrointestinal wall motion.

A saline fixture evaluates the capsule antenna in a conductive environment.

Saline Wireless Test

A saline fixture evaluates capsule antenna performance in a conductive environment.

Six internal air channels and a probing grid support robotic palpation validation.

Embedded-Channel Phantom

Six internal air channels and a probing grid support robotic palpation of soft phantoms.

BLE, IMU and compact stacked boards connect sensing to feedback control.

Embedded Electronics

Bluetooth, an IMU, and compact circuit boards link capsule sensing to feedback control.

Multimodal Flexible Sensors

Polyimide and gold structures support temperature, pressure, and impedance sensing.

A micro-LED assembly supports optical transducer integration.

LED Optical Stimulation

A miniature LED assembly delivers light for localized optical stimulation in the capsule.

An impedance analyzer and channel switches connect multiple capsule transducers.

Four-Channel Sensing

An impedance analyzer and channel switches connect four miniature sensing transducers.

Ceramic antenna placement and matching components reduce the PCB footprint.

Antenna and Matching Layout

Ceramic antenna placement and matching components reduce the wireless board footprint.

Custom Capsule Circuitry

Custom compact circuit layouts integrate electronics within the limited capsule footprint.

Pitch and two coil-pair currents define the magnetic torque model.

Four-Coil Actuation Model

Capsule pitch and two coil-pair currents determine the model of magnetic actuation torque.

A residual GP guides sampling before a compact nominal model is fitted for control.

FEA to Compact Surrogate

A residual GP guides offline sampling before a compact nominal model is fitted for control.

The nominal torque model allocates two coil-pair currents within hardware limits.

Bounded Current Allocation

The nominal torque model allocates two coil-pair currents within hardware current limits.

FEA comparisons quantify nominal-model torque discrepancy away from the training position.

Displacement Sensitivity

FEA comparisons quantify nominal-model torque errors away from the training position.

Adaptive ratio preference improves tracking in the tested 20°–30° reference trials.

Adaptive Current Preference

Adaptive current-ratio preference improves tracking in the tested 20°–30° reference trials.

Finite element analysis resolves the actuator dome deformation under combined loads.

DEA Deformation Simulation

Finite element analysis resolves deformation of the actuator dome under combined loads.

IMU Motion Sensing

Embedded IMUs recover shared motion as deformation propagates through a soft phantom.

Three-axis gyroscope projections and cross-correlation estimate propagation delay.

Coherence and Delay Recovery

Gyroscope projections and cross-correlation estimate motion delay between distributed IMUs.

Multimodal Delay Comparison

Model, vision, inertial, and coherence signals recover relative timing between sensors.

Sliding windows track a programmed change in propagation delay.

Tracking a Delay Transition

Sliding-window analysis tracks a programmed transition in motion propagation delay.

Repeated phantom trials preserve the ordering of imposed 2, 4 and 6 s delays.

Repeated Delay Trials

Repeated phantom trials preserve the ordering of imposed 2, 4, and 6 second motion delays.

Pressure, temperature, and impedance signals track feeding and digestion.

In-Vivo Sensor Signals

Pressure, temperature, and impedance measurements track feeding and digestion in vivo.

Capsule Robot Magnetic Navigation

We develop external magnetic actuation for capsule motion and controlled contact with soft surfaces. Programmable coatings enable rolling and yaw steering, while a complementary four-coil platform regulates pitch with model predictive control and IMU–camera fusion.

Objective: Control capsule orientation and locomotion while preserving internal space for sensing payloads.
Significance: Stable motion and contact support targeted sensing and future capsule interventions.
Result: Benchtop studies demonstrate rolling on varied surfaces and pitch regulation with reduced oscillation. The coating and pitch studies use separate platforms.

Coherence Detection with IMU

We study how unaligned inertial sensors can recover propagating motion on deformable surfaces. Canonical maximization of coherence combines each IMU’s three gyroscope axes, and cross-correlation estimates the delay between sensors.

Objective: Recover coordinated motion and changes in propagation timing from distributed IMUs.
Significance: Alignment-independent sensing provides a foundation for capsule-based monitoring of gastrointestinal motility.
Result: Phantom tests preserved the ordering of 2, 4, and 6 s delays and tracked a programmed delay transition.

Magnetic Palpation

We aim to combine magnetic capsule positioning with controlled tissue contact to measure local mechanical properties. Supporting robotic palpation experiments provide contact models and validation methods for this capsule research direction.

Objective: Develop magnetic palpation that links contact excitation and sensing to local stiffness assessment.
Significance: Mechanical measurements could complement visual capsule examination with information about tissue properties.
Result: A robot-arm and voice-coil benchmark demonstrated stiffness contrast and subsurface-channel mapping in soft phantoms. Capsule magnetic palpation remains in development.

Surrogate Model

We develop compact magnetic torque models for capsule pitch control. Finite-element analysis supplies training data, and a small nominal model predicts torque during bounded allocation of two coil-pair currents.

Objective: Connect FEA-informed modeling to real-time magnetic control under current limits.
Significance: Compact models reduce online computation while retaining the nonlinear dependence on capsule angle and coil currents.
Result: Adaptive current allocation reduced mean tracking RMSE from 4.65° to 1.38° (20°–30° targets; three trials per condition).

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