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# Photonics Startup Eyes Wearables With Laser Spectrophotometer Chip

October 08, 2022 by Jake Hertz

## The company leverages micro-transfer printing (mTP) for a new high-density laser spectrophotometer chip.

One of the reasons smartwatches have thrived in the wearable market (in contrast to, say, AR/VR glasses) is that these devices provide continuous health monitoring. To do this, smartwatches generally rely on optical monitoring techniques such as photoplethysmography and spectrophotometry.

##### The smartwatch market was valued at over $30 billion in 2021. That figure is expected to jump to over$150 billion by 2030, according to Acumen Research and Consulting

Wearable developers are investing heavily in such optical technology advances to improve and expand health monitoring capabilities. On Sept. 22, startup Rockley Photonics made a splash in the smartwatch industry by introducing a new high-density laser spectrophotometer chip.

### What is Laser Spectrophotometry?

Rockley’s new technology relies on spectrophotometry, one of the standard optical methods for health monitoring. Spectrophotometry is a non-invasive technique to measure biomarkers in blood based on light absorption. The technique works by combining two tools: a spectrometer, which produces light of a desired wavelength, and a photometer, which measures the intensity of light.

##### Diagram of a laser spectrophotometer. Image courtesy of LibreTexts

The spectrometer sends a specific wavelength of light through the user’s skin while the photometer sits on the other side of the skin and measures the intensity of the light that makes it to the other side. Only a certain amount of light will be absorbed based on the level and concentration of certain analytes in the body. By measuring the intensity of the received light, the spectrophotometer can determine these analyte concentrations.

### Rockley Releases Laser Spectrophotometer Chip

This week, photonics startup Rockley announced a new laser spectrophotometer chip for wearables.

One of the most significant aspects of the release is the chip’s use of micro-transfer printing (mTP), a method that integrates extremely small and heterogeneous materials with a high degree of accuracy. According to Rockley, the new chip family is the world’s first mTP spectrophotometer chip, and with it comes big advantages.

##### The mTP process enables much smaller laser arrays. Image courtesy of Rockley Photonics

The company claims mTP enables unprecedented laser density in its photonics integrated circuits used for biosensing. With the mTP process, the new chip will integrate a 4-micron-thick, laser-generating membrane. The result is the so-called world’s highest-density, broad-wavelength laser spectrophotometer chip.

Rockley cites several potential applications for this chip, including thinner wearables, smart clothing, and AR/VR headsets.

### Rockley Takes Miniaturization to the Next Level

Covering 1,000 nanometers of spectrum, the new spectrophotometer chips are the industry's smallest for broadband infrared wavelength laser spectrometry, according to Rockley. Additionally, the company claims its chips have a smaller area than other LED-based solutions for wearables, reducing manufacturing costs for these devices.

Using its mTP technology, Rockley plans to further reduce the size and increase the density of its spectrophotometer chips. The new silicon-photonics-based biosensing chips using mTP are slated for rollout in the first six months of 2024.

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