Derivative works — US Patent 11871811

Defensive Disclosure and Prior Art Generation for Rapid-Entry Footwear Technology

Publication Date: April 30, 2026
Reference Patent: U.S. Patent No. 11,871,811 B1
Subject Matter: Rapid-entry footwear utilizing a unitary rear stabilizer and a plurality of elastic elements to enlarge the foot opening.

This document details novel derivative concepts, alternative embodiments, and cross-domain applications of the core technologies described in U.S. Patent 11,871,811 ('811 patent). The purpose of this disclosure is to place these concepts into the public domain, thereby establishing them as prior art to preclude future patenting of these and obvious variations thereof.

Derivatives Based on Independent Claim 1

Core Concept: A rapid-entry shoe with a unitary stabilizer and at least two separate elastic elements positioned forward of the rear portion and separated by non-elastic material.

Derivative 1.1: Shape-Memory Alloy (SMA) Stabilizer with Thermochromic Indicator

Axis: Material & Component Substitution
Enabling Description: The stabilizer, conforming to the "unitary structure" as claimed, is fabricated from a nickel-titanium alloy (Nitinol). At a predefined transition temperature (e.g., 30°C, slightly below body temperature), the Nitinol is in its martensitic phase, rendering it highly flexible and malleable. This allows the rear portion of the shoe to deform with minimal force for foot entry. As the wearer's body heat raises the stabilizer's temperature above the transition point, it reverts to its pre-programmed, rigid austenitic phase, providing firm heel support. The upper material adjacent to the stabilizer is impregnated with a thermochromic pigment that changes color (e.g., from grey to blue) to provide a visual confirmation that the stabilizer has achieved its rigid, locked state. The elastic elements are standard elastomeric gores.

graph TD
    A[Foot Insertion Begins] --> B{Stabilizer at Ambient Temp < 30°C};
    B --> C[SMA Stabilizer in Flexible Martensite Phase];
    C --> D[Heel Deforms for Easy Entry];
    D --> E{Wearer's Foot Transfers Heat};
    E --> F[Stabilizer Temperature > 30°C];
    F --> G[SMA Stabilizer Transforms to Rigid Austenite Phase];
    G --> H[Heel Support is Locked];
    F --> I[Thermochromic Pigment Activates];
    I --> J[Visual Color Change Confirms Lock];

Derivative 1.2: Magnetorheological (MR) Fluid-Based Variable-Tension Gores

Axis: Material & Component Substitution
Enabling Description: The "plurality of elastic elements" are replaced with sealed, flexible bladders containing a magnetorheological (MR) fluid. These bladders are positioned where traditional elastic gores would be. An embedded microcontroller, powered by a piezoelectric generator in the shoe's heel, controls a series of micro-electromagnets surrounding each bladder. In the default (off) state, the MR fluid is liquid, and the bladders offer low resistance, allowing the foot opening to expand easily. Upon detecting full foot insertion via a pressure sensor in the insole, the microcontroller activates the electromagnets. The applied magnetic field dramatically increases the viscosity of the MR fluid, causing it to behave like a semi-solid. This action "stiffens" the gores, securing the foot. The tension can be adjusted via a smartphone application, which communicates with the microcontroller via Bluetooth Low Energy (BLE).

sequenceDiagram
    participant User as User's Foot
    participant Sensor as Pressure Sensor
    participant MCU as Microcontroller
    participant MRE as MR Fluid Gores

    User->>+Sensor: Inserts foot
    Sensor->>+MCU: Foot-in-place signal
    MCU->>+MRE: Apply magnetic field
    MRE-->>-MCU: Viscosity Increases
    MRE-->>-User: Gores stiffen, securing foot

Derivative 1.3: Cryogenic-Rated Footwear for First Responders

Axis: Operational Parameter Expansion
Enabling Description: The rapid-entry system is adapted for footwear intended for use in extreme cold (-50°C to -100°C) and hazardous material handling. The unitary stabilizer is molded from a cryo-grade glass-fiber-reinforced polyether ether ketone (PEEK), which maintains its structural integrity and impact resistance at extremely low temperatures. The "plurality of elastic elements" are fabricated from a silicone-based elastomer specifically formulated for low-temperature flexibility, preventing the material from becoming brittle. The non-elastic upper material is a multi-layer composite of aramid fiber (for puncture resistance) and a closed-cell foam insulation layer. This construction allows for rapid donning of protective boots over a standard inner boot in an emergency, even when materials are stiff from cold.

graph TD
    subgraph Boot Construction
        A(Sole: Cryo-Rated Rubber)
        B(Stabilizer: GFR-PEEK)
        C(Elastic Elements: Low-Temp Silicone)
        D(Upper: Aramid/Foam Composite)
    end
    A --integrates with--> B
    B --supports--> D
    D --interrupted by--> C
    subgraph Performance
        E{Environment: -70°C}
        F[Foot Insertion] --> G[Silicone Elements Stretch]
        G --> H[PEEK Stabilizer Guides Heel]
        H --> I[Boot Secured]
    end
    C --maintains_flexibility_in--> E
    B --maintains_rigidity_in--> E

Derivative 1.4: Medical - Articulating Ankle-Foot Orthosis (AFO)

Axis: Cross-Domain Application
Enabling Description: The invention is embodied in an AFO for patients with drop foot or mobility challenges. The "unitary stabilizer" is a rigid, L-shaped polypropylene strut that provides posterior support and extends from under the heel up to the calf. The "forward portion" is a soft, padded cuff that wraps around the shin. Instead of laces or complex straps, the AFO employs two distinct elastic elements, separated by the non-elastic cuff material. One elastic element is oriented vertically along the anterior of the shin, while the second is angled at approximately 45 degrees, connecting the shin cuff to the footplate. This arrangement allows the patient to easily slide their foot in. The pre-set tension of the angled elastic element then provides the necessary dorsiflexion assist, while the vertical element ensures a snug fit around the shin. This design facilitates one-handed application of the brace.

classDiagram
    class AFO {
        +polypropylene_stabilizer
        +padded_shin_cuff
        +footplate
        +vertical_elastic_element
        +angled_elastic_element
        +don_brace()
        +provide_dorsiflexion_assist()
    }
    AFO : +stabilizer : "Unitary Strut"
    AFO : +elastic_elements : "Plurality with different vectors"

Derivative 1.5: Aerospace - Emergency Seat Egress Harness

Axis: Cross-Domain Application
Enabling Description: The concept is applied to a lightweight, rapid-donning restraint harness for crew members in a spacecraft. The "stabilizer" is a semi-rigid, carbon-fiber composite frame that conforms to the shape of a crew member's back and shoulders. The "upper" is a system of fire-retardant Nomex webbing straps. A "plurality of elastic elements," made from high-tensile strength elastomeric cord, are integrated into the chest and thigh straps. These elastic sections are separated by the non-elastic webbing. To don the harness, the crew member simply slips their arms through the shoulder loops and pulls it on like a vest. The elastic elements expand to accommodate their body and flight suit, and then contract to provide a secure initial fit. Final tensioning is achieved with a single, central buckle, but the initial fit-up is automatic and rapid, saving critical seconds during an emergency egress procedure.

graph TD
    subgraph Donning Sequence
        A(Sling Harness Over Shoulders) --> B(Pull Down Over Torso);
        B --> C{Elastic Chest/Thigh Straps Expand};
        C --> D{Carbon Fiber Stabilizer Self-Aligns on Back};
        D --> E{Elastic Straps Contract to Secure Harness};
        E --> F(Engage Single Central Buckle for Final Tension);
    end

Derivative 1.6: IoT-Enabled Prophylactic Footwear for Diabetics

Axis: Integration with Emerging Tech
Enabling Description: This iteration integrates an IoT sensor suite into the rapid-entry shoe design for preventative diabetic foot care. The unitary stabilizer houses a multi-axis accelerometer and a gyroscope to monitor gait symmetry, stability, and potential falls. The non-elastic upper incorporates a grid of flexible pressure sensors and temperature sensors, providing a real-time map of potential ulceration hotspots. The elastic elements are made of a conductive elastomer, which acts as a strain gauge to measure medial and lateral foot swelling throughout the day. All sensor data is processed by a low-power MCU embedded in the sole and transmitted via BLE to a patient's smartphone app and a clinician's dashboard. An AI model in the cloud analyzes trends and sends alerts for risky conditions (e.g., sustained high pressure at one point, abnormal temperature gradients, or sudden swelling).

graph TD
    subgraph Shoe_Sensors
        A[Inertial Measurement Unit in Stabilizer]
        B[Pressure/Temp Grid in Upper]
        C[Conductive Elastomer Strain Gauges]
    end
    subgraph Data_Flow
        A --> D{Onboard MCU};
        B --> D;
        C --> D;
        D --(BLE)--> E[Smartphone App];
        E --> F[Cloud AI Platform];
        F --> G[Clinician Dashboard];
        F --> H[Patient Alerts];
    end

Derivative 1.7: Failsafe De-Tensioning System for Industrial Safety Boots

Axis: The "Inverse" or Failure Mode
Enabling Description: This footwear is designed for workers in environments with entanglement risks (e.g., conveyor belts, rotating machinery). The unitary stabilizer is standard, providing protection. However, the "plurality of elastic elements" are connected to the upper via a shear-pin mechanism. Under normal walking and flexing forces, the pins hold the elastic elements, and the shoe functions as designed. If a tensile force exceeding a calibrated threshold (e.g., >100 Newtons) is applied, as would occur during an entanglement event, the shear pins are designed to fracture. This instantly decouples the elastic elements from the upper, causing the foot opening to expand to its maximum possible size and allowing the boot to be pulled off the foot, preventing the worker from being dragged into the machinery. The shear pins are color-coded for different force ratings and are user-replaceable.

stateDiagram-v2
    [*] --> Normal
    Normal: Shoe is secure
    Normal --> Entangled: Entanglement event
    Entangled: Tensile force > 100N
    Entangled --> Released: Shear pins fracture
    Released: Elastic elements decouple
    Released --> [*]: Foot is free from boot

Derivatives Based on Independent Claim 10

Core Concept: A rapid-entry shoe with a unitary stabilizer and a plurality of elastic elements, where at least two have longitudinal axes at different angles relative to a vertical axis, facilitating forward flexion.

Derivative 10.1: Asymmetric Torsional Control for Athletic Footwear

Axis: Material & Component Substitution
Enabling Description: This derivative is for a court shoe (e.g., for basketball or tennis) requiring high lateral stability. The unitary stabilizer is a carbon fiber heel counter that wraps forward and is bonded to the midsole. The shoe features two primary elastic elements on each side, their axes angled differently. The first, more vertical elastic element is made of a high-modulus elastomer providing strong resistance to stretching, controlling ankle support. The second, more horizontal element, is made of a lower-modulus elastomer, allowing for easier expansion over the instep during entry. The different angles and different elastic moduli work in concert. During a cutting motion, the force vector is primarily resisted by the high-modulus, vertically-angled element on the load-bearing side, while the other elements maintain fit. This provides directional, asymmetric support that adapts to athletic movements while still allowing rapid entry.

graph TD
    subgraph LateralSide
        A[High-Modulus Vertical Elastic Element]
        B[Low-Modulus Angled Elastic Element]
    end
    subgraph MedialSide
        C[High-Modulus Vertical Elastic Element]
        D[Low-Modulus Angled Elastic Element]
    end
    subgraph Forces
        E(Foot Entry) --> F{Low-Modulus Elements (B, D) Stretch Easily};
        G(Lateral Cut) --> H{High-Modulus Element (A) Resists Lateral Roll};
    end
    A & B --> I(Secure Fit)
    C & D --> I
    F --> I
    H --> J(Enhanced Stability)

Combination Prior Art Scenarios with Open Standards

Combination 1: Rapid-Entry Shoe with FIDO2/WebAuthn Authentication

Concept: A rapid-entry shoe is equipped with an NFC chip and a piezoelectric pressure sensor array integrated into the insole. This system acts as a hardware security token. The unique pressure signature of a user's foot-strike and weight distribution, captured at the moment of insertion ("gait-printing"), is used as a biometric factor.
Integration with Open Standard: The shoe's firmware implements the FIDO2/WebAuthn open standard. When the user steps into the shoe and takes a step, the shoe can authenticate the user to a FIDO2-compliant web service (e.g., a corporate network, a payment system) via NFC tap or BLE. The combination of the physical token (the shoe) and the biometric (the gait-print) provides two-factor authentication. This creates prior art for footwear-based, hands-free authentication systems.

Combination 2: Parametric Shoe Design using OpenSCAD

Concept: The design of the rapid-entry shoe, specifically the geometry of the unitary stabilizer and the placement, angle, and size of the cutouts for the elastic elements, is defined as a parametric model.
Integration with Open Standard: The model is created and published using OpenSCAD, an open-source, script-based CAD program. This allows anyone to download the source file and customize the shoe design for a specific foot size, width, or desired level of support by simply changing variables in the script (e.g., stabilizer_height=60; gore_angle_1=75; gore_angle_2=40;). The resulting STL files can be used for 3D printing custom stabilizers or manufacturing molds. This places the concept of a fully open-source, parametrically-defined rapid-entry shoe into the public domain.

Combination 3: ROS2-Integrated Mobility Aid

Concept: The medical AFO variant (Derivative 1.4) is enhanced with an Inertial Measurement Unit (IMU) and joint angle sensors.
Integration with Open Standard: The AFO's onboard computer runs a node in the Robot Operating System 2 (ROS2), an open-source suite of software libraries and tools for building robot applications. The AFO publishes its sensor data (pronation, supination, angle, gait phase) to the ROS2 network over Wi-Fi. This allows seamless integration with other ROS2-enabled assistive devices, such as a smart cane or an exoskeleton. For example, the AFO could signal the user's intent to stand, pre-activating motors in a robotic walker. This creates prior art for a modular, interoperable ecosystem of open-source mobility aids based on the rapid-entry footwear structure.