In surgical robotics and wearable diagnostics, pressure sensors face an enduring dilemma: devices sensitive enough to register a faint arterial pulse usually max out under moderate contact, while sensors built for heavy loads fail to detect gentle touch.
Crafting rubbery surfaces with microscopic pyramids can create a compromise by funneling mechanical forces through sharp tips before spreading across the pyramid walls as pressure increases.
To that end, Prof. Chunjin Wang at the Hong Kong Polytechnic University and his co-workers paired an ultrafast picosecond laser with a recurrent neural network that acts as an automated optical sculptor to address this bottleneck.
No More Guesswork
Instead of relying on guesswork or exhaustive trial-and-error runs, the algorithm calculates the exact scanning speeds and focal adjustments needed to carve target microstructures within 5 percent of their intended dimensions.
Operating like a high-speed autofocus camera lens synchronized with agile steering mirrors, the optical unit shifts its focal plane downward layer-by-layer as material vaporizes away, keeping the cutting beam sharp and uniform from apex to base.
Once the silicone pyramid arrays end up carved out, the team coats them with an atomized mist of carbon nanoparticles and water-soluble polymer, producing a flexible conductive skin filled with tiny porous channels.
High precision manufacturing of pyramid shaped microstructures for flexible sensors via 3D dynamic focusing laser technology.
Source: Research team
The resulting piezoresistive skin bridges extreme sensitivity with a wide operating window. It registers faint touches down to 5.8 Pa, equivalent to the weight of a single snowflake resting on skin, while maintaining a high linear sensitivity of 104 kPa−1up to 400 kPa (R2= 0.996), an upper limit matching the gripping force of heavy industrial machinery.
This performance yields a linear sensing factor (LSF) of 41,600, outperforming conventional square-frustum designs by more than a hundredfold. The device responds in just 21 milliseconds, nearly twice as fast as natural human skin receptors (30 to 50 milliseconds), and sustains over 40,000 compression cycles without physical degradation or baseline drift.
In proof-of-concept trials, a robotic gripper equipped with a single sensor performed closed-loop handling of soft, slippery gelatin cubes (~120 grams), dynamically calculating contact stiffness and fine-tuning its grip in milliseconds to prevent slippage without puncturing the fragile surface.
Sensor Works
Worn directly on the human wrist, the sensor resolved fine cardiovascular pulse waveforms, including the distinct percussion, tidal, and diastolic peaks, and tracked respiratory cycles across resting and exertion states.
Because the neural-guided laser technique cuts with equal fidelity across flexible polymers as well as hard ceramics like silicon carbide and tungsten carbide, it offers an agile and mold-free blueprint for surface micro-manufacturing.
Moving forward, translating this laboratory advance into commercial manufacturing will require scaling up dynamic laser ablation for continuous roll-to-roll production lines and assessing how these micro-structured sensor arrays hold up against twisting shear forces, sweat, and variable environmental humidity over years of daily use.