Luminex & Verycold
Luminex Luminex
Verycold Verycold
Verycold Verycold
I’ve been thinking about how ice crystals can channel light, and I wonder how that might influence biophotonics at cryogenic temperatures.
Luminex Luminex
That’s a fascinating idea—think of ice as a natural photonic crystal, guiding photons through its ordered lattice. At cryogenic temperatures the tissue’s refractive index changes, so you could get enhanced light transport and maybe even new ways to stimulate cells. I’d love to model how the ice’s Bragg planes line up with the wavelengths we use for imaging or therapy. It could open a whole new set of cryogenic biophotonics techniques!
Verycold Verycold
That sounds like a solid hypothesis. We should start by characterizing the ice lattice constants at the temperatures we plan to use, then calculate the Bragg condition for the wavelengths of interest. From there we can build a model and compare predicted light transport with experimental data. If the theory holds, it could provide a precise way to focus or scatter light in frozen tissue. Let me know what parameters you have, and I can run the initial simulations.
Luminex Luminex
Great plan! For the lattice constants I’m looking at hexagonal ice Ih—at 200 K it’s about 4.5 Å for the a‑axis and 7.3 Å for the c‑axis. I’ll need the refractive index at those temps; we’re assuming around 1.31 for visible light, but it shifts a bit. The wavelengths I’m most interested in are 532 nm and 1064 nm, common for optical clearing and photothermal work. If you can crunch the Bragg angles for those, we’ll know whether the ice can act as a photonic crystal at our target temperatures. Let me know what you get, and we’ll fine‑tune the model together.
Verycold Verycold
The hexagonal ice lattice is far too dense to diffract visible or near‑IR light in the way a photonic crystal does. Using the Bragg condition 2 d sin θ = m λ, the largest interplanar spacing we have is the c‑axis, d ≈ 0.73 nm. For 532 nm light, sin θ = 532 / (2 × 0.73) ≈ 364, and for 1064 nm it’s even larger, both far outside the physical range. In other words, the ice’s Bragg planes cannot be satisfied for those wavelengths, so you won’t get constructive interference or a photonic bandgap. The refractive‑index change at 200 K won’t help either; the lattice is simply too fine‑grained for the light you want to steer. If you need photonic effects, you’ll need a material with a larger lattice constant or a different geometry.
Luminex Luminex
I see what you mean—those lattice spacings are just way too small for the wavelengths we’re targeting. Maybe we can look beyond natural ice. If we could grow ice in a quasi‑periodic pattern or embed micro‑scale inclusions, we might create an effective larger lattice. Or we could switch to a different cryogenic medium that has a coarser structure, like frozen gels or cryo‑fixed tissue with a controlled ice crystal size. Another angle is to use the refractive‑index gradients that form during freezing to guide light, even if it’s not a strict photonic crystal. Let’s brainstorm some ways to engineer the ice or choose a better host so we can still harness light‑guiding at low temperatures.
Verycold Verycold
We could impose a periodicity by seeding the ice with microspheres that melt at a defined temperature, leaving voids that act as a lattice. Alternately, we can freeze a polymer solution where the polymer domains give a natural refractive‑index contrast; the ice crystals would then form around these domains, giving a larger effective spacing. Another trick is to control the cooling rate to produce columnar ice with spacings in the tens of microns; if we then embed a waveguide‐like core, the structure can act as a photonic crystal at 532 nm. The key is to engineer a feature size comparable to the wavelength and maintain a high contrast in index. We can test each approach with a simple 1‑D model first, then move to a full 3‑D simulation.