Imagine a tool capable of moving cells and microparticles without physical contact, utilizing only light. It’s like a sci-fi tractor beam, except it’s much more precise and operates at a much smaller scale. That’s essentially what optical tweezers are — a technology that uses laser beams to trap and manipulate tiny objects.

Now, thanks to a team of researchers at MIT, this technology is reaching new heights. The innovation is a silicon-photonics-based optical phased array (OPA) which could open the door to significant progress in medical diagnostics, biological research, and even in-vivo (in the body) applications. To make it even better, it’s pretty cheap.

Optical tweezers

Optical tweezers use the force exerted by light to trap microscopic objects, including cells and biomolecules, allowing scientists to manipulate these tiny particles with incredible precision. They’re not a new invention — they’ve been used since the 1970s and have revolutionized biological research.

This non-contact tool is so important because it can trap, move, and control tiny objects without causing damage. Optical tweezers are used to study the mechanical properties of cells, examine DNA interactions, and measure forces at the molecular level. This technology helps researchers to explore fundamental biological processes and understand disease mechanisms.

But there’s a catch: they’re expensive.

They rely on bulky, expensive optical components and sophisticated laboratory setups, making them inaccessible to many researchers. The current methods also face limitations in versatility, particularly when it comes to manipulating cells in a sterile environment or reaching deeper into biological samples.

This is where the new invention comes in.

The research team’s new optical tweezing system was developed using an approach called optical phased arrays. These integrated OPAs don’t require a bulky setup and can be typically deployed on a single chip. This offers a compact, scalable, and cost-effective solution that’s much more cost-effective than conventional setups.

The advantages of integrated OPAs go beyond compactness. Traditional optical tweezers often struggle with operating in sterile environments. Until now, the “tractor beam” that was generated was close to the setup. This meant after every sample, there was contamination and the chip had to be thrown away. The new OPA-based tweezers can trap particles 5 millimeters above the silicon-photonics chip’s surface — more than two orders of magnitude greater than previous integrated systems.

It needs some calibration, but it works

Jelena Notaros, one of the study authors, says this opens up new ways for robust chip-based optical tweezers. There are still critical challenges, particularly for complex setups. However, Notaros and colleagues addressed this by employing a calibration technique that can be customized based on different types of samples and setups.

The researchers demonstrated the efficacy of the system by trapping and manipulating polystyrene microspheres, a common proxy in biological experiments. The spheres, about 10 microns in diameter, were successfully trapped and tweezed at a distance of 5 millimeters from the chip surface. The OPA setup was able to move and control the microspheres precisely.

Then, the team also tested the tweezers on biological cells. They manipulated mouse lymphoblast cells, performing a technique often used to assess the mechanical properties of cells, which can offer insights into disease mechanisms. This experiment marked the first time that cells were manipulated using single-beam integrated optical tweezers. The team also stretched cells using optical tweezers, a process that has far-reaching implications for cancer research, disease diagnostics, and cellular biomechanics. Stretching cells allows researchers to measure their elasticity, an important factor in understanding how cells respond to mechanical stress and identifying pathological changes in diseased cells.

The new type of optical tweezers has broad applications in fields like biomedical research, diagnostics, and in-vivo manipulation. They can be used for high-throughput cell sorting, enabling rapid disease screening, and precise cell manipulation, such as deforming cells to study their mechanical properties in diseases like cancer.

Future advancements could include wearable diagnostic devices for real-time in-vivo applications and holographic multi-beam systems for handling multiple particles simultaneously, making them invaluable for complex biological studies. The ability to mass-produce these tweezers at low cost could greatly expand access to this powerful technology, furthering research in biophysics, drug development, and medical diagnostics.

The findings were published in the journal Nature Communications.