The morning mist of "Xiuxiu Forest" always carried a faint herbal fragrance. These volatile organic compounds released by "light moss," mixing with the thin Martian atmosphere's water vapor, condensed into tiny droplets in the morning light, clinging to the silicon carbide window frames of the maintenance station, refracting pale blue light patterns of the "Information Geometry Field Theory" created by Yue'er during her lifetime--those intertwined curves resembled three entwined galactic rivers: one with the precise, cool arc of mathematics, one reflecting the exact light spots of lithography, and one wrapped in the flowing luster of capital, precisely the metaphor for the lives of Mozi, Yue'er, and Xiuxiu.
Xiu'an squatted in the backyard of the maintenance station, carefully spraying nutrient solution on the "light moss" seedlings. She wore a silver-gray protective suit with a small tin-drop badge pinned to her sleeve--a favorite accessory of her great-grandmother Xiuxiu during her lifetime, crafted from discarded EUV lithography machine tin target material, engraved with a subtle light path representing the propagation trajectory of 13.5nm extreme ultraviolet light. As Xiuxiu's direct descendant, Xiu'an inherited her great-grandmother's eyes: the edge of her iris had a faint golden pattern that would contract like an optical lens aperture whenever she focused on observing "light moss." Elders always said, "This is Xiuxiu's gaze; it brightens when looking at light."
"Sister Xiu'an, the old lab bench in the front yard needs cleaning; it seems to have some of your great-grandmother's old things," the intern Xiao Xia's voice came through the communicator, tinged with excitement. "We found a leather notebook in the drawer, its cover yellowed with age, seems like... a diary?"
Xiu'an's hand paused, the nutrient spray nozzle almost touching the "light moss" seedlings. She stood up, brushed the dust off her protective suit, and quickly walked to the front yard. The old lab bench in the maintenance station was personally built by Xiuxiu years ago, using a discarded DUV lithography machine base. The edge of the tabletop still bore scratches from adjusting the optical system in 2028--when Xiuxiu's team conquered immersion DUV technology, they accidentally scraped it with a wrench. Later, shedeliberately carved a small "light" character at the scratch site.
In front of the lab bench, Xiao Xia held a deep brown leather notebook, carefully blowing off the dust. The notebook cover bore no text, only a laser-engraved tin-drop pattern, identical to the badge on Xiu'an's sleeve. As Xiu'an took the notebook, the moment her fingertips touched the cover, she suddenly felt a familiar palpitation--just like when she first touched her great-grandmother's EUV photoresist sample as a child, thatwonderful feeling ofas if able to "hear the sound of light."
"Let me see." Xiu'an gently opened the notebook, only to find the pages blank. The paper was made from "light moss" fiber,with a faint green tint, feeling moreresilience than ordinary paper. But no matter how sheflipping through, each page showed only clean paper surface, without any writing.
"Did great-grandmother not write anything?" Xiao Xia said, somewhat disappointed. "Or... was invisible ink used?"
Xiu'an didn't speak. She remembered what her mother once said: "Your great-grandmother loved creating 'technical Easter eggs'; her things always hid secrets that could only be activated under specific conditions." She placed the notebook in the sunlight on the lab bench, carefully observing the paper's texture--in theoblique morning light, shediscovered extremely subtle microbial traces at the edge of the paper, like some kind ofinvisible patterns formed by colonies.
"Go get the 'photosynthetic bacteria' culture dish," Xiu'an said to Xiao Xia. "Photosynthetic bacteria" was a microorganism cultivated by Xiuxiu years ago,symbiosis with "light moss," capable of secreting special enzymes to decompose specific organic compounds--while studying her great-grandmother'sexperimental records, Xiu'an had seenrecorded of this bacteria,the labeled purpose at the time was "for encryption and decryption of information storage."
Xiao Xia quickly brought the culture dish. Xiu'an dipped a sterile cotton swab in a small amount of "photosynthetic bacteria" culture solution and gentlyapplied it on the notebook's first page. Somethingmagical happened: as the culture solutionpenetrated,faint black handwriting gradually appeared on the paper, strokessmooth and powerful, bearing Xiuxiu's distinctive handwriting style--"October 15, 2025, cloudy. Departing from Eindhoven today, the clouds outside the airplane window resembled the mercury lamp spots of DUV lithography machines,scattering cold white light. Colleague Mark asked me why I insisted on returning to China. I said, 'Light has no borders, but the machines that create light do.' He didn't understand, and I didn't explain further--some paths can only be walked alone."
"It's biodegradable ink!" Xiao Xiaexcitedly shouted. "Using degradable chitosan carriersencapsulating color-forming groups; only the enzymes secreted by 'photosynthetic bacteria' can decompose chitosan, making the writing appear!"
Xiu'an nodded, gently brushing her fingertips over the writing, as if touching her great-grandmother's mood when she wrote these words. She knew this biodegradable ink was Xiuxiu'spatented technology--originally developed to prevent lithography technologydata leakage, Xiuxiu's team created this ink for recording coreexperimental data, readable only under specificmicrobial environment, with "photosynthetic bacteria" serving as the "key" to this ink.
As the "photosynthetic bacteria" culture solution continued to be applied, more writing appeared. Xiu'an sat at the lab bench, reading page after page, as if following her great-grandmother's footsteps, retracing thoseturbulent times.
"March 7, 2026, clear. Today marks the 100th day of joining the domestic DUV team. The mercury lamplight source stability still isn't satisfactory; three consecutive experiments failed due to light spotdrift. Old Zhou in the team said, 'Why not just buy core components from ASML?' I disagreed--you can buy components, but not the roots of technology. Called Yue'er in the evening; she was in Princeton's library, saying, 'Xiuxiu, try approaching it from symmetry; light paths must hide symmetric codes.' I suddenly remembered the Galois groups she once taught me; perhaps the symmetric structure of optical systems couldtruly solve the light spotdrift problem."
Reading this, Xiu'an's eyes moistened. She remembered what her mother said: great-grandmother and Yue'er's great-grandmother were "light and string partners"--when Xiuxiu couldn't solve opticalchallenges, Yue'er always found breakthroughs through mathematical methods; and Yue'er's theoretical research often gained new inspiration from Xiuxiu's technicalpractice. Xiu'an took an old folder from the drawer containing Xiuxiu'sback thenexperimental sketches,one of which depicted a symmetric optical lens structure,with Yue'er's annotations in red pen beside it "Galois groupcorrespondence relationship," handwritinggraceful yet firm.
"May 20, 2027, rainy. Immersion DUV finally succeeded! Adding a layer of water between the lens and silicon wafer increased resolution from 28nm to 14nm instantly, like opening a new window for light. When today's wafer run succeeded, the young team members cried, but I remained calm--not unmoved, but knowing this was just the beginning. Mozi sent me a message today: 'Xiuxiu, your light illuminates paths capital dares not tread.' He didn't know it was his capital that gave us theconfidence to create light--last week, through Swiss channels, he helped us purchase precision nozzles from Germany, solving our urgent need."
Xiu'an read this passage, recalling the story of Mozi's great-grandfather--that "capital poet" who stirred global capital markets with goldfutures, yet invested all profits into high-tech industries. She took a small Uplate from the maintenance station's display cabinet, a gift from Mozi to Xiuxiu, containing records ofback then "String Light Fund"capital flow supporting lithography machineR&D, each entry labeled "for the exploration of light."
The diary pages turned, time flowing gently through therevealed handwriting. Xiu'an saw Xiuxiu's joy when breaking through EUVlight source power: "July 12, 2030, 3 a.m. EUVlight source powerstably exceeded 250 watts! The moment the laser hit the tin drop, I saw 13.5nm extreme ultraviolet light, like the universe's first light atbirth, pure andwarm. Yue'er rushed to the lab overnight; holding aspectrometer, she said, 'Xiuxiu, the mathematical model corresponding to this light'swavelength completely matches my Information Geometry Field Theory.' Mozi also came, bringing a bottle of champagne but didn't open it--he said, 'We'll drink when your EUV lithography machines achieve global market share leadership.'"
She also saw Xiuxiu's resilience facingtechnology embargo: "January 8, 2032, snowy. ASML announcedceased supplying optical lenses to us, citing 'international policyimpact.' Actually, I know they're afraid--our 7nm EUV has begunmass production,snatched their orders. Today in the team meeting, I said, 'Don't fear; we'll make the lenses ourselves.' Yue'er mailed me her new paper containing mathematical modeling methods for aspherical lenses; Mozi helped us acquire a small German optical workshop with veteran craftsmen whoback thenmanufactured EUV lenses. Some walls, when dismantled, become roads."