This month, lots of (mostly-) failed experiments trying to develop a workflow for 3d-printed templating of silk casting and indigo dyeing. Some tests have shown promise for being able to indigo-dye template-cast silk hydrogel, but when the hydrogel dries it shrinks so much that it completely loses its shape. Running a new silk fibroin prep now to try some alternative approaches next…

Just by way of exposing the high failure rate of this kind of experimentation I thought I’d paste in my very cursory lab notes from the past few weeks, just below this slideshow of photos from the test work.

23 Sep 2025

repeated 6 Sep SF prep with 5g silk, in oven at 8:55am

20 Sep 2025

Unconcentrated SF solution in fridge now almost fully gelled – still flows just a bit

• Used bulb pipette to pour small quantity of ethanol in two places on kanshi plate, including upper left corner and right mid
• Used pipetter to lay in <1ml mostly gelled SF in upper left corner of plate
• Added 2ml partly reduced indigo solution to what looked like just under 20ml mostly gelled SF and stirred with pipette tip; used pipetter to lay in 5+ ml blue SF gel in lower and right areas of the plate, including some not pre-wetted with ethanol, with some smears over kanji tops
• Tried to tap-level and then leaving out to dry
• 22 Sep dried out no coverage left, took cell phone photo

18 Sep 2025

• Injected 100ul indigo solution into 3ml unconcentrated SF solution; let oxidize for ~15 min in fridge then poured into bottom of 200ml beaker to let dry (took cell phone photo)
• 20 Sep ~10am dried SF in bottom of beaker just very pale blue (took cell phone photo). Seems to adhere well to glass beaker bottom; covered in 2-3mm 0.5MeO, sealed beaker with parafilm and will leave overnight
• 22 Sep changed sup to DI water leaving sealed overnight

Idea: try injecting 100ul indigo solution into 5ml SF solution, then casting to dry film

• If this looks good, could either continue with blue lettering, …
• Or could print gold PLA letters positive in white PLA “tray” then cast dyed SF film as the “paper” background
• Gold dust?

Took refreshed indigo stock solution out of oven – leaving on bench overnight but should stir and rewarm ~hour(s) before each use?

17 September 2025

• Lower eppendorf of concentrated SF solution gelled in fridge (upper did not)
• Put 1ml of the refreshed indigo stock on it and leaving overnight in fridge; put a fresh 1ml on Thu 18 Sep; 20 Sep took cell phone photo then changed sup to DI water and back in fridge; 23 Sep has turned blue – took cell photo and changed water (had tinted brown)
• Also put SF solution in next PLA tile – left radical is all unconcentrated, right is something like 30% concentrated, after ~5 minutes covered in 50%MeO, covered with unstretched parafilm and weighed down to leave overnight; drained on Thu 18 Sep ~1pm and did two rounds of indigo dyeing, then into stirred beaker of DI water

16 September 2025

• Put ~150ul concentrated SF solution in left radical of new PLA form and will let dry (took photo on Olympus stereo)
• Also injected 100ul indigo solution into 5ml DI, shook/vortexed, and will leave overnight uncapped to see if blue water forms…
• No blue – possible that indigo stock solution expired. Looking in the flask there was significant blue sediment on the bottom so possibly it all oxidized out. At ~1pm agitated to put the indigo back in suspension, added another 1.25g fructose, then flask back at 60C and will check in an hour…
• ~2:15pm indigo stock now seems better – injecting into DI does immediately turn blue – letting some blue water settle overnight to see what it looks like tomorrow (took cell phone photo)
• Put dried SF film tile into DI beaker with stirring to leave overnight; on 18 Sep ~1pm did two rounds of indigo dyeing then into stirred beaker of DI water

14 September 2025

• Put 2ml indigo solution into 15ml conical
• “injected” 100ul concentrated SF solution into indigo solution with pipetter
• Let sit for ~20 minutes
• Used pipetter to try to skim off indigo sup, leaving what might be settled SF solution at the bottom
• Filled tube with ~14ml DI water, capped to let sit
• 16 Sep – doesn’t look like there is a solid pellet left X
• 20 Sep after settling undisturbed for a few days there seem to be two phases – took cell phone photo. Can this be used to make indigo thin films? Should I push it through a syringe filter, dry out, and then resuspend in ethanol perhaps?
• None of it passed through an 0.2um syringe filter – took before and after cell phone photos, will see if possible to recover dry powder from filter membrane

12 September 2025

• Carefully pipetted concentrated SF into Ri mold in “dish” PLA
• Tried to pipette 50% MeO on top with minimal disturbance of SF, left just a bit of space at top
• Covered with unstretched parafilm and weighed down with small beaker of water
• ~10:40am
• Top up 0.5MeO ~3pm to leave overnight
• Pour out remaining 0.5MeO and place whole thing in beaker of DI water & stir plate ~4pm Saturday; refresh DI water ~2pm Sunday
• ~1:40pm Tuesday remove PLA, drip dry and blow a little house nitrogen – photo taken on Olympus stereo
• Put 1ml indigo solution in PLA well, cover with unstretched parafilm and weigh down with beaker of water, letting incubate in 60C oven
• SF hydrogel seems to have taken in the brown liquid (Olympus stereo zoom photo taken; no liquid remained under the parafilm cover ~1pm Wednesday) but now not sure the stock solution still had much leuco-indigo. Stirring now in a beaker of DI water to see what happens, might need to try dyeing again after regenerating the indigo stock solution…
• Indigo stock solution better after refreshing – at ~2:15pm took PLA tile out of beaker and put ~1.5ml on it, then put it back, covered, into the oven. Indigo solution immediately turned somewhat blue so will try refreshing at ~5 minute intervals
• Changed indigo 4 times then left overnight in still beaker of DI water (weighed down with stir bar, facing up)
• 20 Sep after several days, wiped rim and used kimwipes to pat dry; took Olympus stereo zoom photo and now leaving out to dry
• 22 Sep has shrunken too much after drying – took Olympus photo

11 September 2025

• Put several ml methanol in a 15ml conical
• Used pipetter to gently deposit a bead of concentrated SF in the very bottom, trying not to mix it with the methanol (in future don’t do the final pipetter plunge)
• Left overnight
• Changed solution to water, left overnight
• Put 1ml indigo dyeing solution into conical and incubate ~11:00am Fri 12 Sep; new 1ml ~12:30pm; new 1ml ~1:30pm; flush several times and leave on DI water ~2:45pm; change DI water ~4pm Saturday; drain ~2pm Sunday, leave tube open to dry (does not look like indigo penetrated significantly into silk hydrogel bead)
• 16 September ~1:40pm it does not look like the pellet has shrunk much at all – took cell phone photo, will leave for a few more days; 22 Sep now has completely nuggetized and pulled away from tube walls

10 September 2025

• Used 3k MW centrifuge concentrator (50 ml conical) to try to condense 4ml solution from SF prep
• After ~30 min at 4C had about 1ml left above the filter

7 Sep 2025

• set up imaging on stereo scope for upcoming tests

Working ideas – inlay:

• Press dyed hydrogel chunks into kanji forms and let dry
• Press dyed hydrogel chunks into kanji forms and attempt freeze-drying
• Try solvent exchange with dyed hydrogel chunks and then place/press into kanji forms
• Mix dyed hydrogel chunks (+gold?) in optical resin; fill kanji forms
• Mix dried dyed hydrogel chunks (+gold?) in optical resin; fill kanji forms
• Press dyed hydrogel chunks (hydrated or dried) into kanji forms, cap w/ optical resin

Working ideas – forming:

• Try using pipetter to deposit a bead of SF solution at bottom of methanol tube
  • If it doesn’t disperse, try filling kanji form with SF and immerse open in methanol
  • then rehydrate to water
  • then immerse in indigo dyeing solution?
• Try using pipetter to deposit a bead of SF solution at bottom of indigo tube?
  • incubate warm?
  • If it disperses, what happens if you let a 1:1 mixture dry?
• Try using indigo “blue water” for last step of dialysis of SF solution?

6 Sep 2025

Made 5.15g SF prep with 20.6ml of 9.3M LiBr (16.64g); placed in 60C at 8:21am. Also made 125ml indigo solution with 1.25g fructose, 0.63g indigo, and 2ml 50% w/w NaOH.

To do: 1) try indigo dyeing small chunks of “expired” SF hydrogel and then packing them into PLA voids; let dry and see; 2) make a test 3D-print for an MeOH reaction cell along the lines of 3 Oct 2024 – plan on applying double-sided adhesive and then exacto-cutting outlines? try this with concentrated SF solution…