Shareholders' equity - Schedule of stockholder's equity (Details) |
Sep. 30, 2026
USD ($)
shares
|
Sep. 30, 2026
EUR (€)
shares
|
Aug. 26, 2026
USD ($)
shares
|
Aug. 03, 2026
USD ($)
shares
|
Jul. 29, 2026
USD ($)
shares
|
Jul. 17, 2026
USD ($)
shares
|
Jun. 11, 2026
USD ($)
|
Jun. 03, 2026
USD ($)
|
Jun. 03, 2026
EUR (€)
|
May 22, 2026
USD ($)
shares
|
May 16, 2026
USD ($)
shares
|
May 12, 2026
USD ($)
shares
|
Mar. 11, 2026
USD ($)
shares
|
Feb. 13, 2026
USD ($)
shares
|
Jan. 29, 2026
USD ($)
shares
|
Jan. 22, 2026
USD ($)
shares
|
Jan. 16, 2026
USD ($)
shares
|
Jan. 14, 2026
USD ($)
shares
|
Jan. 09, 2026
USD ($)
shares
|
Jan. 06, 2026
USD ($)
shares
|
Jan. 02, 2026
USD ($)
shares
|
Dec. 31, 2025
USD ($)
shares
|
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Share capital | $ 36,064,786.19 | € 31,438,880.7 | $ 26,911,786 | |||||||||||||||||||
| Additional paid-in capital | $ 459,200,000 | $ 541,300,000 | ||||||||||||||||||||
| Number of shares (in shares) | shares | 314,388,807 | 314,388,807 | 235,670,864 | |||||||||||||||||||
| Capital increase by ordinary shares | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Share capital | $ 2,098,619 | $ 2,046,974 | $ 415,170 | $ 628,234 | ||||||||||||||||||
| Additional paid-in capital | $ 45,800,000 | $ (1,800,000) | $ (400,000) | $ (600,000) | ||||||||||||||||||
| Number of shares (in shares) | shares | 18,288,220 | 17,690,365 | 3,500,000 | 5,392,100 | ||||||||||||||||||
| Capital increase by ordinary shares | Capital increase, one | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Share capital | $ 337,888 | $ 1,042,823 | $ 1,081,489 | |||||||||||||||||||
| Additional paid-in capital | $ (300,000) | $ 6,600,000 | $ 6,900,000 | |||||||||||||||||||
| Number of shares (in shares) | shares | 2,886,452 | 8,907,689 | 9,226,931 | |||||||||||||||||||
| Capital increase by ordinary shares | Capital increase, two | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Share capital | $ 48,411 | $ 1,080,197 | $ 361,147 | |||||||||||||||||||
| Additional paid-in capital | $ 0 | $ 6,900,000 | $ (300,000) | |||||||||||||||||||
| Number of shares (in shares) | shares | 413,553 | 9,226,931 | 3,081,200 | |||||||||||||||||||
| Capital increase by employee RSU | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Share capital | $ 167 | $ 2,035 | $ 47 | $ 1,749 | $ 3,427 | $ 192 | ||||||||||||||||
| Additional paid-in capital | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | ||||||||||||||||
| Number of shares (in shares) | shares | 1,465 | 17,500 | 400 | 15,212 | 29,500 | 1,650 | ||||||||||||||||
| Capital increase by employee Stock Option | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Share capital | $ 1,530 | $ 2,768 | $ 133 | |||||||||||||||||||
| Additional paid-in capital | $ 0 | $ 0 | $ 0 | |||||||||||||||||||
| Number of shares (in shares) | shares | 13,425 | 24,200 | 1,150 | |||||||||||||||||||
| Retained earnings charged on share premium | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Additional paid-in capital | $ (220,800,000) | $ (220,838,268) | € (190,148,327) | |||||||||||||||||||
| Share-based payments | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Additional paid-in capital | $ 10,900,000 | |||||||||||||||||||||
| Net Issuance of warrants | ||||||||||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||||||||||
| Additional paid-in capital | $ 65,200,000 |