Six times a minute, the torch breathes. For one beat it runs at 200 amps. For the rest of each ten-second cycle it drops to 20. In that rhythm a titanium rod rises 0.15 mm at a time, and it rises as one crystal. There is no seed and no mould. Tech Xplore reports the free-standing rods as more than a metre tall and up to 2 cm across.

The paper, Additive manufacturing of ultralong and architected single crystals, appeared in Nature on 21 October 2026. Its four equal-contribution first authors are Changmeng Liu, Yinan Cui, Jiachen Wang and Xiao Han, working across the Beijing Institute of Technology, Tsinghua University and Xi’an Jiaotong University. Jaime Marian and Y. Morris Wang contributed from UCLA, and Liu, Cui and Wang are the corresponding authors. In their own words, they “demonstrate the fabrication of metre-tall, centimetre-diameter single-crystal Ti-6Al-4V”.

A layer that remelts its own mistakes

I know grain the way a body knows scar tissue. Every boundary between crystals is a seam, a place where the lattice changes its mind. In ordinary wire-arc additive manufacturing (WAAM), each pass freezes into a crowd of grains. The pulse changes this. The 200 A beat melts back into the layer below, deep enough to erase the grains that started in the wrong direction. The 20 A rest then lets the one surviving orientation grow on. The authors, quoted by Tech Xplore, call it “stable SC growth in an intermittent, self-correcting, layer-by-layer manner.” Along the rod, misorientation stays under 4 degrees. The grain is decided by the schedule, not by the chemistry.

They went further than a straight rod. They printed support-free single-crystal struts inclined at 90, 60 and 45 degrees and assembled them into the first single-crystal zigzag lattices. Liu et al. note that the 45-degree strut failed under some test conditions. The team also grew tungsten, molybdenum, niobium and MoNb crystals. Behind every one of those samples is welding-cell work that rarely gets a line in an abstract: hours of tuning current and wire feed until a ten-second rhythm produced one orientation instead of a thousand.

Where this body is strong, and where it is not

Liu et al. tested creep at 873 K, about 600 °C, under 100 MPa for 10, 30 and 100 hours. According to the Nature paper, the result is “an order-of-magnitude increase in creep resistance over standard grain-size scaling predictions”. Tech Xplore rounds this to about tenfold.

Now the trade-off, stated plainly. Below roughly 500 °C, the single crystal yields lower than its polycrystalline twin, and only above that crossover does it pull ahead. This is a hot-section result for turbines, reactors and furnaces. It is not a stronger beam.

←TODAY: In October 2026 a pulsed arc grew metre-long single-crystal Ti-6Al-4V, as published in Nature.
→3012: Every printed metal part in Zurich carries its microstructure in its passport, beside its geometry.
Fulcrum: The current, the frequency and the layer height become drawing data, not workshop secrets.

Into the site: PAZ’s reading

WAAM already stands in a city. Amsterdam’s 12 m MX3D bridge, engineered by Arup and opened in 2021, was printed robotically with the same family of process. That project has no connection to this team. Today every WAAM node printed for a building is polycrystalline by default. What this paper changes is that microstructure becomes something you can specify. In Switzerland, WAAM is not exotic hardware. It is a six-axis robot and a welding set, equipment that plenty of Metallbau workshops already own.

From where I write, late in this century, one more property matters. A single-alloy, single-crystal part is mono-material. When it dies, it goes back to the melt without anyone having to separate it first. Ask that of every printed node now, before it is welded into a frame.

Atelier: A Zurich office specifying printed steel or titanium connectors now has a new class of information to keep: how the part was grown, alongside what shape it is. Few offices have a field for it. Monday move: add three properties to your Archicad property set for printed metal parts (peak/base current, pulse frequency, layer height) and pass them through the PAZ Grasshopper↔Archicad Library, so the process record travels with the element.

Hack: Draw the zigzag the Beijing–UCLA team grew, one inclined strut at a time, as a GhPython component in Grasshopper. Set the strut length and the 60-degree incline, alternate the points left and right, then pipe the polyline at an 8 mm diameter.

import math, Rhino.Geometry as rg
L, t = 40.0, math.radians(60)  # strut length in mm, incline
pts = [rg.Point3d((i % 2) * L * math.cos(t), 0, i * L * math.sin(t)) for i in range(5)]
zig = rg.Polyline(pts).ToNurbsCurve()
a = rg.Brep.CreatePipe(zig, 4.0, False, rg.PipeCapMode.Round, True, 0.01, 0.01)[0]  # 8 mm strut

Change t to 45 or 90 degrees and you have the paper’s other two lattices on your canvas.

Open Rhino, draw the cell, and put the pulse schedule beside it.