iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Ultraviolet light can move a tiny silica bead through the ordinary liquid crystal 5CB without adding a photo-responsive chemical. In the 2017 experiment by Yoshiko Takenaka and Takahiro Yamamoto, 365 nm light was absorbed partly by a polyimide-coated glass surface, converted to heat, and used to expand the liquid crystal. That expansion displaced the bead; the light did not push it directly. Motion occurred while 5CB was in its nematic phase, reversed toward the starting position after the light was turned off, and reached only about half a bead diameter under the reported conditions.
The direct finding: heat, not a light-powered molecular switch
The work is best understood as a photothermal displacement experiment. A focused or directed UV beam warms the polyimide layer on one wall of a liquid-crystal cell. The nearby 5CB expands as its temperature rises. Because the bead is suspended in that confined liquid, the expanding material changes the local flow and pressure field and carries the bead away from its initial position.
This distinction matters. The authors did not report a radiation-pressure effect, optical trapping, or a chemical additive that changes shape when illuminated. Their samples used ordinary 4-cyano-4′-pentylbiphenyl (5CB), with no added photo-isomerizing molecule. The proposed chain is light absorption by polyimide, conversion of light to heat, thermal expansion of 5CB, and mechanical displacement of the bead.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
The original paper, Light-induced displacement of a microbead through the thermal expansion of liquid crystals, appeared in Soft Matter 13 (2017), pages 1116–1119. It was first published online on 10 November 2016 and has a DOI of 10.1039/C6SM02324J. Read the Royal Society of Chemistry article for the full images and methods.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
How the proposed mechanism works
1. Polyimide absorbs part of the UV
The glass cell has a polyimide coating. Under the reported 365 nm illumination, that coating absorbs some of the incident energy and warms. The coating is therefore a transducer: it turns optical input into a local temperature increase at the liquid-crystal boundary.
2. The 5CB volume changes with temperature
5CB has temperature-dependent dimensions. In the experiment, the material was nematic at 25 °C and became isotropic at 40 °C, with a nematic–isotropic transition temperature of 35 °C. A heated region in the nematic sample consequently expands and displaces surrounding liquid.
3. The bead follows the resulting displacement
Silicon-dioxide (SiO2) beads approximately 10 µm in diameter were suspended in the cell. The bead responds to the bulk movement and confinement of the liquid crystal rather than to a direct photon “push.” When illumination stops, the temperature gradient relaxes and the bead starts moving back toward its original location.
The authors note that anisotropic thermal expansion could still deserve further analysis. That qualification means the simple heating-and-expansion explanation is the dominant interpretation of this demonstration, not a claim that every directional detail of the flow has been solved.
What the researchers put in the cell
Bead preparation
The starting colloid was a dispersion of approximately 10 µm SiO2 microbeads in ethanol. The ethanol was mixed with 5CB and then evaporated. This left the beads dispersed in the liquid crystal rather than in a volatile carrier.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Cell construction
The mixture was loaded into test cells made from glass. Three of the tested cells had the polyimide coating used for photothermal conversion; a fourth cell omitted that coating. The comparison allowed the researchers to separate heating at the coated surface from effects that might arise simply because the beam entered the sample.
Temperature conditions
Measurements were made at two temperatures chosen on opposite sides of 5CB’s phase transition. At 25 °C, the sample was nematic. At 40 °C, it was isotropic. These are the experiment’s stated conditions, not universal operating limits for every 5CB cell or every bead size.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesPhase and coating controls
The four-cell and two-temperature comparison is the clearest evidence for the proposed mechanism. The outcomes reported by Takenaka and Yamamoto were:
| Condition | Observed result | What it indicates |
|---|---|---|
| 25 °C, polyimide-coated cell | Beads moved in all three tested coated cells | Nematic 5CB plus an absorbing coating supports displacement |
| 25 °C, cell without polyimide | No bead movement in the fourth cell | Coating-mediated photothermal conversion is important in this setup |
| 40 °C, polyimide-coated or uncoated cells | No movement in any of the four cells | The reported effect was absent when 5CB was isotropic |
The result does not prove that an isotropic liquid crystal can never be moved by heating. It shows that, under these cell, bead, illumination, and temperature conditions, the observed motion required the nematic state and the coated surface.
Wavelength tests rule out a simple brightness explanation
The researchers compared 365 nm UV with visible wavelengths at the stated equal light intensity. They observed motion with 365 nm but not with 470, 525, 590, or 625 nm light.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
| Illumination wavelength | Reported observation at equal stated intensity |
|---|---|
| 365 nm UV | Bead displacement observed in the qualifying nematic, coated-cell tests |
| 470 nm | No observed motion |
| 525 nm | No observed motion |
| 590 nm | No observed motion |
| 625 nm | No observed motion |
These wavelength observations support a role for the optical absorption of the particular polyimide and cell assembly. They should not be read as a universal rule that all polyimides respond only to UV, because absorption depends on coating chemistry, thickness, substrate, and beam intensity.
What the bead actually did
Displacement scaled with UV intensity
The paper reports that displacement distance increased in proportion to UV intensity. In the authors’ abstract, the relationship is stated exactly as: “The distance of the displacement was proportional to the intensity of the UV light.” This is a result for their measured range and geometry, not a calibrated law for arbitrary cells.
Travel was short
In the experiments, the bead moved no more than approximately 50% of its own diameter. For a bead near 10 µm across, that corresponds to a distance on the order of 5 µm, but the paper’s reported performance metric is the fraction of bead diameter, and the exact travel depends on the individual observation.
Motion reversed after shutoff
When the UV source was switched off, the bead began returning toward its initial position. The return is consistent with the local thermal expansion relaxing as the cell cools. It also distinguishes the effect from a permanent chemical transformation of the bead or liquid crystal.
Longer travel was only proposed
The authors suggested that moving the illuminated spot could trace a bead over a longer path. They presented that as a future possibility, not as a demonstrated transport distance. No continuous pump, conveyor, or automated trajectory was established in the reported work.
Free tools Windows power users keep installed
One-click scans. No signup required.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Why an infrared test is informative
In an additional control, an infrared laser moved beads in a cell that lacked the polyimide coating. The authors interpret this result, together with the coating, phase, and wavelength tests, as evidence that heating and liquid-crystal thermal expansion dominate over molecular alignment effects in their demonstration.
The infrared observation does not make the coating irrelevant. Rather, it shows that a different wavelength and absorber can supply heat through another route. The original 365 nm result depends on the specific polyimide-coated cell, while the infrared test demonstrates that direct thermal input can also produce displacement when the sample remains in the appropriate state.
Reported workflow, step by step
The following sequence summarizes the published preparation and observation. It is a description of the experiment, not a claim that a bead purchase alone reproduces it.
- Prepare the colloid. Disperse approximately 10 µm SiO2 microbeads in ethanol.
- Combine with 5CB. Mix the bead–ethanol dispersion with 5CB.
- Remove ethanol. Evaporate the ethanol before filling the test cell so the final suspension is in 5CB.
- Assemble comparison cells. Use polyimide-coated glass for the photothermal condition and include an uncoated cell as a control.
- Set the phase. Observe near 25 °C for nematic 5CB and near 40 °C for isotropic 5CB, remembering that 35 °C was the stated transition temperature for this material in the paper.
- Illuminate. Apply 365 nm UV at controlled intensity and record bead position. For wavelength controls, use 470, 525, 590, and 625 nm at the stated equal intensity.
- Measure and reverse. Compare displacement with intensity, then turn the source off and watch for motion back toward the starting position.
A faithful reproduction would also need the cell geometry, coating process, optical alignment, thermal environment, bead concentration, and intensity range used in the paper. Those details determine how much heat reaches the liquid and how strongly the walls constrain expansion.
What this result does—and does not—establish
- Established in the reported setup: UV illumination can displace a microbead in nematic 5CB when a polyimide-coated glass surface is present.
- Supported by controls: The effect depends on the nematic phase and on a surface or illumination route that converts optical energy into heat.
- Measured scale: Displacement was limited to about half a bead diameter in these observations.
- Not demonstrated: A finished microfluidic pump, heat sensor, actuator, long-range transporter, or commercial device.
- Not shown: A universal wavelength threshold, a universal intensity-to-distance calibration, or operation with every liquid crystal and coating.
Those boundaries are important because a short laboratory displacement can be physically useful without yet being a practical machine. Scaling requires control of heat dissipation, phase stability, bead interactions, cell sealing, and repeatability over many cycles.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Potential applications are future directions
Microfluidic pumping
Takenaka and Yamamoto suggested that controlled thermal expansion could eventually contribute to a microfluidic pump. A pump would require repeatable net flow or pressure generation, not merely the back-and-forth movement of one tracer bead. The published experiment did not build or test such a pump.
Heat sensing
They also proposed heat sensors in which bead displacement serves as a visible indicator of liquid-crystal expansion. Turning that idea into a sensor would require calibration against temperature, a defined response time, and a known operating range. None of those device specifications were established by the proof of concept.
Particle tracking
Because the bead follows local expansion, it can act as a tracer for what happens inside a confined liquid-crystal layer. That makes the method potentially useful for studying thermal flows, provided the tracer’s own size and surface interactions are accounted for.
How to read the result in context
A news account published by Chemistry World on 28 November 2016 used the phrase “Crystal expansion makes light work of moving microbeads” and emphasized the same central distinction: thermal expansion, rather than a light-responsive additive, moves the particles. Read the Chemistry World context.
The bibliographic record is available through PubMed under the same paper title. See the PubMed record. Together with the full Royal Society of Chemistry article, these sources identify the dates, authors, materials, and limits without turning the laboratory observation into a consumer specification.
Practical checklist for evaluating similar claims
- Ask whether the light is being absorbed and converted to heat, or whether a photo-responsive molecule is changing shape.
- Check the liquid-crystal phase at the stated temperature; nematic and isotropic behavior can differ sharply.
- Look for a coated-versus-uncoated cell control.
- Check whether wavelength comparisons used equal intensity and whether the absorber’s spectrum was characterized.
- Separate demonstrated displacement from proposed applications such as pumping or sensing.
- Keep the reported travel distance tied to the bead diameter and experimental geometry.
For this experiment, those checks lead to a precise conclusion: a polyimide-coated cell, nematic 5CB, and 365 nm illumination produced a small, reversible bead displacement through photothermal liquid-crystal expansion.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
