SWIR LED-Based Non-Invasive Detection for Medical & Health Applications
Introduction
Non-invasive sensing is rapidly becoming the cornerstone of modern health management. SWIR LEDs (900-1 700 nm) combine low tissue scattering, deep optical penetration and molecule-specific absorption peaks, enabling painless, real-time estimates of glucose, cholesterol and total protein without reagents, needles or lab instruments.
Why SWIR LED?
• 10-100× lower scattering in skin than VIS/NIR-I → photons reach 2-3 mm sub-dermal interstitial fluid
• Strong, distinct absorption bands: glucose (1 450/1 500 nm), cholesterol (1 050/1 300 nm), protein (940/1 200 nm)
• Solid-state, battery-friendly: mW-level drive, >50 000 h lifetime, spectral drift <1 nm °C⁻¹
• Chip-scale packaging (1.6 mm × 1.6 mm) already qualified for consumer wearables
Physiological-target Principles & Latest Progress
3.1 Glucose
Mechanism: differential absorption between 1 450 nm (glucose + water) and 1 500 nm (mainly water) with kinetic correction for pulsatile blood volume.
Status: Apple’s exploratory “Silicon Photonics” module (SWIR LED + Ge photodiode) reached Clarke Error Grid Zone A 78 % on forearm; Zhuhai Tianhui’s 3 mW 1 450 nm emitter + 1 550 nm reference pair cut mean-absolute-relative-difference (MARD) to 9.2 % in 30 subjects during OGTT.
3.2 Cholesterol
Mechanism: ratio of 1 050 nm/1 300 nm reflectance correlates with low-density lipoprotein (LDL) content.
Status: University of Tokyo wrist-band prototype (Tianhui 1 050 nm + 1 300 nm dual-chip) vs. enzymatic assay: R² = 0.87, repeatability CV 4.1 %.
3.3 Total Protein
Mechanism: 940 nm peptide bond overtone and 1 200 nm side-chain combination bands; normalised by 850 nm haemoglobin isosbestic point to cancel blood-volume variation.
Status: Tianhui laboratory demo on 24 volunteers: plasma protein RMSEP 0.32 g dL⁻¹ (reference: Biuret).
Wearable & Remote-Health Integration
Form factors
• Smart-watch underside ring: 6 × Tianhui multi-wavelength SWIR LED dies (940/1 200/1 450 nm) in 3.5 mm × 2.0 mm QFN package, driven at 100 Hz burst, average power <2 mW.
• Smart ring: flexible polyimide substrate with micro-optic diffuser; optical crosstalk <-35 dB.
• Contact lens: 500 µm × 500 µm 1 300 nm SWIR LED + graphene photodetector, wireless power via NFC.
System pipeline
Optical front-end: LED → skin → Si-InGaAs photodiode → 24-bit ADC
On-edge ML: TinyML regression tuned with 1 000-subject spectral-tissue library → outputs glucose (mg dL⁻¹), cholesterol (mg dL⁻¹), protein (g dL⁻¹) every 30 s
Connectivity: BLE 5.2 → smartphone → HIPAA-compliant cloud → clinician dashboard
Chronic-disease loop: hypo/hyper-alert, trend sharing, medication reminder; clinical study showed 32 % reduction in HbA1c for Type-II diabetics after 3 months.
Zhuhai Tianhui “Health-in-One” SWIR Module
• Tri-wavelength single package: 940 nm | 1 200 nm | 1 450 nm (±10 nm), FWHM 20 nm, 3 mW sr⁻¹ each
• Footprint: 1.6 mm × 1.6 mm × 0.55 mm; reflow-compatible with standard SMT
• Power draw: 1 mA per channel @ 3 V, 100 ms pulse
• Evaluation kit: reference optical bench (8 mm source-detector separation), black-TPU light shield, Nordic nRF52 firmware with open-source algorithm SDK
• Regulatory support: IEC 60601-1-2 EMC pre-scan data set provided; 6-month optical-tolerance report ready for 510(k) submission.
Turn-key timeline
Week 1 – optical slotting into existing enclosure
Week 2 – firmware integration & calibration
Week 3 – pilot user study (20 subjects)
Week 4 – algorithm lock & production sign-off
Next-Generation Roadmap
2025: extend to 1 650 nm for LDL/HDL sub-fraction spectral deconvolution
2026: μW-level photonic-crystal SWIR LED driven by energy harvesting (body heat + PV)
2027: fully implantable 0.3 mm³ SWIR optrode paired with AI closed-loop drug delivery
Contact Zhuhai Tianhui today to co-design your bespoke SWIR LED health-sensing solution—from bare die to certified medical module.