NP8i – ON-THE-GO NEUROSTIMULATION
Modular, Wearable TENS & Closed-Loop Neurostimulation
CATEGORY
- Medical Devices
- Wearable
- Neurotechnology
Philip Muiico.
AxioBionics LLC
SERVICES
- FEASIBILITY + PRODUCT DESIGN
- FULL-CYCLE PRODUCT DESIGN
- HARDWARE + PCB DESIGN
- MECHANICAL DESIGN
- FIRMWARE DEVELOPMENT
- EVT, DVT, PVT
PROJECT TIMELINE
THE CHALLENGE
NeuroStim Solutions engaged Axio Electronics to develop NP8i: a belt-worn, battery-operated TENS/NMES device patients can self-administer at home—no clinician needed. Key requirements included:
- Form Factor: iPhone-sized, wearable on a belt clip.
- User Interface: Full 5″ touchscreen to select and adjust any stimulation protocol.
- Dual-Use Electrodes: Same pads must deliver TENS/NMES and record EMG signals.
- Closed-Loop Control: Automatic adjustment of stimulation parameters based on real-time EMG feedback.
- Electrode Verification: Bioimpedance triangulation to guide pad placement and detect failures.
- Safety & Compliance: Medical-grade materials and full regulatory approval for home use.
THE KEY HURDLES INCLUDED:
- •Preventing interference between high-voltage stimulation and low-amplitude EMG recording.
- •Designing bioimpedance circuitry and algorithms for accurate electrode-placement mapping.
- •Creating a clinician-grade UX on a wearable touchscreen for non-professional users.
- •Ensuring 12-hour operation on a compact battery while maintaining IP67 water resistance.
- •Meeting FDA 510(k) and CE-mark requirements for a Class II medical device.
THE OPPORTUNITY
Patients with chronic pain or neuromuscular disorders often require frequent clinic visits for TENS or NMES therapy. NP8i promised to:
- Empower patients with a clinician-standard, closed-loop system at home
- Enhance therapy adherence through guided setup and real-time feedback
- Reduce healthcare costs by minimizing in-clinic stim sessions
- Generate rich EMG and impedance data for remote clinician review
FEATURE SETS
- •Modular Belt-Wearable Design – Quick-release clip and electrode port
- •5″ High-Res Touch LCD – Intuitive protocol selection & real-time graphs
- •Dual-Mode Electrodes – TENS/NMES delivery + EMG acquisition
- •Closed-Loop Control – Auto-adjust amplitude/frequency via EMG feedback
- •Bioimpedance Triangulation – Step-by-step pad placement guidance & fault alerts
- •Bluetooth & WiFi Sync – HIPAA-compliant data upload to cloud portal
- •12-Hour Battery Life – 4,000 mAh rechargeable cell with thermal management
- •IP67 Rating – Dust- and water-resistant for reliable home use
- •AES-256 Encryption – Secure storage & transmission of patient data
- •FDA 510(k) & CE-Mark – Certified for safe, at-home clinical use
GALLERY
THE SOLUTION
Axio Electronics approached the challenge with a full-cycle product design strategy — from feasibility analysis and electrical design to firmware development and production readiness.
BLE
Support Any Keyboard
USB
Act as Wired Keyboard + Writing Data Transfer
WIFI
Sync to Google Drive / Dropbox
MONOCHROME LCD
High-Contrast, Lag-Free Display
20-HOUR BATTERY
4700mAh Long-Lasting Performance
ADJUSTABLE BACKLIGHT
Write in Any Lighting
MAGNETIC STAND
Ergonomic Viewing Angles
FLEXIBLE STORAGE
Save Over 1 Million Words
INTUITIVE CONTROL
Three Push-Buttons
SECURITY
AES-128 Encryption
CERTIFICATION
FCC & CE Compliance
BODY
ABS Plastic
OUR APPROACH
Mechanical Engineering Strategy
Ergonomic Belt Clip: Stable, vibration-free wear during daily activities
Sealed Enclosure: Polycarbonate shell with silicone overmolding (IP67)
Quick-Release Electrode Port: Tool-free pad swaps and cleaning
Thermal Management: Internal heat spreaders for battery & ICs
Mechanical Engineering Process
CAD modeling & ergonomic studies with neurosurgeon feedback
CNC prototypes for fit, weight, and comfort trials
Finite-element drop and strap-tension testing
Final injection-mold tooling
Hardware Design
Dual HV Channels: Up to 100 mA constant-current stimulation drivers
Low-Noise EMG Amp: 0.1 µV sensitivity with active shielding
Bioimpedance Circuitry: 4-electrode multiplexed measurements
MCU: STM32L4 for real-time control & on-chip DSP
Wireless: BLE 5.2 + 802.11n WiFi with TLS stack
Safety: Over-current, short-circuit protection, medical isolation
EMI Mitigation: Shield cans, segmented grounds, ferrite beads
Firmware Design
Closed-Loop Algorithm: Auto-tunes pulse width/amplitude based on EMG RMS
Impedance Mapping: 3D electrode-placement map, alerts on poor contacts
Touch UI Wizard: Guided setup replicating clinical protocols
Data Logging: Encrypted, timestamped events, waveforms, impedance spectra
EHR Integration: HL7 FHIR support
Secure OTA: Verified bootloader & signed firmware
In-House Prototyping
Form & Fit: SLA + CNC prototypes tested by surgeons & patients
Bench Testing: Waveform accuracy, impedance mapping, thermal profiling
EVT: IEC 60601-1 electrical safety, stimulation & EMG specs
DVT: Six-week IRB-overseen home trial—refined UI & strap design
PVT: Pilot run of 50 units to confirm manufacturing consistency
Challenges:
- Stim-EMG Crosstalk— Time-multiplexed acquisition + local shielding
- False Placement Alerts— Higher sampling density & algorithm smoothing
- Battery Overheat— Graphite spreader + dynamic current throttling
- User Setup Errors— Enhanced wizard with visual & haptic cues
PILOT & PRODUCTION
PILOT & PRODUCTION
After a successful Kickstarter campaign — exceeding 400%+ funding goals within 21 days — Axio Electronics transitioned the BYOK design into mass production with strategic revisions:
Clinical Pilot: 30 patients over 4 weeks — 95% adherence, 88% pain reduction
BOM Optimization: 15% cost savings via alternate electrode supplier & custom ASIC
Regulatory: FDA 510(k) K24XXXXX, CE 0123; ISO 13485-certified manufacture
Factory Test Jig: Automated checks for electrode port, stimulation amplitude, UI calibration
How It Works
Attach NP8i to belt & connect electrodes as guided
Power On and follow setup wizard
Select Therapy; NP8i delivers closed-loop TENS/NMES
Monitor EMG & Impedance in real time; device auto-tunes protocol
Sync Data to cloud portal for clinician review
WHAT CAN
WE CREATE
TOGETHER
DOWNLOAD THE CASE STUDY
Client Testimonial
Philip Muiico
AxioBionics LLC
NP8i has transformed our at-home rehabilitation regimen—patients feel safer, clinicians gain deeper insights, and outcomes have improved markedly.
Axio Electronics