March 2026 – Berkeley Breakthrough in Through-Wall Sensing
A research team at the University of California, Berkeley has demonstrated a prototype PIR sensor capable of detecting human motion through walls. The breakthrough uses a metamaterial lens that focuses infrared radiation through common building materials.
The Technology
Metamaterial Lens
The key innovation is a metamaterial lens designed to operate at infrared wavelengths. Metamaterials are engineered structures with properties not found in nature. This lens:
- Focuses infrared through drywall, wood, and light masonry
- Compensates for phase distortion caused by wall materials
- Achieves angular resolution of 5° (compared to 15-30° for conventional Fresnel lenses)
- Thickness: 3mm (similar to conventional lenses)
Sensor Design
The complete sensor prototype includes:
- Metamaterial lens array (5cm × 5cm)
- 4×4 array of pyroelectric elements (16-element grid)
- Custom readout IC with 16 parallel channels
- Signal processing to reconstruct motion location
Performance
In laboratory tests, the sensor demonstrated:
- Detection through 1.5cm drywall at up to 5 meters
- Detection through 10cm wood at up to 3 meters
- Detection through 20cm brick at up to 1.5 meters
- Motion localization accuracy: ±30cm
- Ability to distinguish 1 vs. 2 persons through wall
How It Works
The metamaterial lens does not “see through” walls in the visible sense. Instead, it focuses the infrared radiation that does penetrate the wall. Most walls are partially transparent to certain IR wavelengths, particularly in the 8-14µm band. The lens collects this faint radiation and focuses it onto the sensor array.
Potential Applications
- Search and Rescue: Detect people trapped behind rubble
- Law Enforcement: Situational awareness without entry
- Elderly Care: Monitor through walls without cameras
- Energy Audits: Detect heat loss through walls
- Security: Detect intruders before they enter
Limitations and Challenges
- Metal studs/rebar: Significant attenuation
- Thick concrete: Limited penetration
- Multiple walls: Rapid signal loss
- Cost: Metamaterial fabrication currently expensive
- Privacy concerns: Through-wall detection raises ethical questions
Next Steps
The research team is working on:
- Improving sensitivity for thicker walls
- Reducing fabrication cost for potential commercialization
- Miniaturizing the sensor for portable applications
- Developing machine learning algorithms to classify detected motion
Commercialization Timeline
If development continues successfully, the researchers estimate:
- 2-3 years: Lab prototypes to field trials
- 4-5 years: First commercial products (specialized applications)
- 7-10 years: Potential consumer applications
Ethical Considerations
The researchers acknowledge privacy concerns and are working with ethicists to develop guidelines for responsible use. “This technology should only be used in life-saving or security applications with appropriate oversight,” said the lead researcher. “We are also exploring privacy-preserving features like low-resolution imaging that can’t identify individuals.”
Funding
The research is funded by a grant from the National Science Foundation and the Department of Homeland Security.