Introduction to Biorobotics and Bionics

Biorobotics is an interdisciplinary field at the intersection of biology and robotics — studying how biological systems can inspire robotic design, and conversely how robotic systems can augment, restore, or study biological function.

Three major application domains define the field:

• Exoskeletons: wearable robotic structures that work in parallel with the human body to augment strength, assist rehabilitation, or restore mobility to individuals with neurological or musculoskeletal impairments
• Prosthetics: robotic replacement limbs that restore lost function after amputation, increasingly controlled by neural signals (myoelectric or brain–computer interfaces)
• Surgical robotics: robotic systems that assist or perform surgical procedures, offering sub-millimetre precision, tremor filtering, and access to anatomically constrained spaces

These domains share common technical challenges: safe physical human–robot interaction, real-time biosignal processing, compliance and force control, and rigorous regulatory approval pathways (FDA 510(k), CE marking).

An exoskeleton is a wearable robotic orthosis that applies forces and torques to the wearer's body segments. Exoskeletons are classified by purpose:

Rehabilitation exoskeletons assist stroke, spinal cord injury, and neurological patients in relearning motor patterns through repetitive, guided movement. Examples: Ekso Bionics EksoGT, Hocoma Lokomat (treadmill gait), ReWalk Personal 6.0.

Augmentation exoskeletons amplify the wearer's strength for industrial or military use, reducing fatigue and injury risk. Examples: Sarcos Guardian XO (industrial), Hyundai H-MEX (logistics).

Partial-assist exoskeletons support a single joint or limb — ankle exoskeletons for drop-foot correction, back-support exoskeletons for manual handling workers.

Key engineering challenges:

• Actuation: Series Elastic Actuators (SEA) or hydraulics provide force-controlled, compliant output safe for human contact
• Intent detection: EMG signals, force/torque sensors in the foot or handle, and IMU-based gait phase estimation detect what the user intends to do
• Ergonomic attachment: misalignment between robot and biological joint axes causes discomfort and can cause injury — kinematic compatibility is critical

Modern myoelectric prostheses measure surface EMG signals from residual limb muscles to infer the user's intended movement. Electrodes placed on the skin detect the electrical activity of contracting muscles; a classifier maps these signals to hand/wrist gestures.

Advanced control approaches:

• Pattern recognition: machine learning classifiers (LDA, SVM, CNN) decode simultaneous multi-degree-of-freedom movements
• Targeted Muscle Reinnervation (TMR): surgically redirects severed nerves to new muscle sites, creating additional EMG control signals for more natural, intuitive control
• Osseointegration: the prosthesis socket is replaced by a titanium implant directly into the bone, improving suspension and enabling bidirectional neural communication via implanted electrodes

Brain–Computer Interfaces (BCI) represent the frontier: Utah electrode arrays or ECoG grids implanted in motor cortex decode movement intentions directly from neural spike trains, allowing paralysed individuals to control robotic arms in 3D space with thought alone (BrainGate consortium, Johns Hopkins APL Modular Prosthetic Limb).

Notable commercial prostheses: Touch Bionics i-Limb, Ottobock Michelangelo Hand, PSYONIC Ability Hand (provides tactile feedback via vibration).

Surgical robots enhance a surgeon's capabilities rather than replacing clinical decision-making. Benefits include: tremor cancellation, motion scaling (large hand movements mapped to tiny tool movements), 3D stereoscopic vision, and access through small incisions (minimally invasive surgery, MIS).

The da Vinci Surgical System (Intuitive Surgical) is the dominant platform with over 7,500 systems installed worldwide. The surgeon sits at a console and manipulates wristed instruments through small port incisions. Endowrist instruments have 7 degrees of freedom — more than the human wrist.

Emerging platforms:

• Hugo RAS (Medtronic): modular, open-platform surgical robot
• Versius (CMR Surgical): small, portable, arm-per-port design for laparoscopic surgery
• Monarch (Auris Health/J&J): robotic bronchoscopy platform for lung biopsy
• MAKO (Stryker): haptic-guided robotic arm for knee and hip arthroplasty

Challenges: latency requirements (<300 ms for teleoperation), sterility and sterilisation, FDA Class II/III regulatory approval, surgeon training, and integration with hospital information systems.