Exhibit 4.1

 



.ZQ|CERT#|COY|CLS|RGSTRY|ACCT#|TRANSTYPE|RUN#|TRANS#   1 COMMON STOCK PAR VALUE $0.001 COMMON STOCK Certificate Number ZQ00000000   THIS CERTIFIES THAT QUANTERIX CORPORATION INCORPORATED UNDER THE LAWS OF THE   STATE OF DELAWARE ** Mr. Alexander David Sample **** Mr. Alexander David   Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample ****   Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander   David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample   **** Mr. Alexander David MR. SAMPLE & MRS. SAMPLE & Shares * * 000000   * * * * * * * * * * * * * * * * * * * * * 000000 * * * * * * * * * * * * * *   * * * * * * * 000000 * * * * * * * * * * * * * * * * * * * * * 000000 * * * *   * * * * * * * * * * * * * * * * * 000000 * * * * * * * * * * * * * * SEE   REVERSE FOR CERTAIN DEFINITIONS David Sample **** Mr. Alexander David Sample   **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr.   Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander   David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample   **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr.   Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander   David Sample **** Mr. Alexander David Sample MR. SAMPLE & MRS. SAMPLE   CUSIP 74766Q 10 1 is the owner of   **000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares***   ***ZERO HUNDRED THOUSAND 000000**Shares*   **000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****0   00000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****00   0000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000   ZERO HUNDRED AND ZERO***   00**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000*   Shares****00000   0**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000   **Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000*   *Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**   Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**S   THIS CERTIFICATE IS TRANSFERABLE IN CITIES DESIGNATED BY THE TRANSFER AGENT,   AVAILABLE ONLINE AT www.computershare.com FULLY-PAID AND NON-ASSESSABLE   SHARES OF COMMON STOCK OF Quanterix Corporation (hereinafter called the   “Company”), transferable on the books of the Company in person or by duly   authorized attorney, upon surrender of this Certificate properly endorsed.   This Certificate and the shares represented hereby, are issued and shall be   held subject to all of the provisions of the Certificate of Incorporation, as   amended, and the By-Laws, as amended, of the Company (copies of which are on   file with the Company and with the Transfer Agent), to all of which each   holder, by acceptance hereof, assents. This Certificate is not valid unless   countersigned and registered by the Transfer Agent and Registrar. Witness the   facsimile seal of the Company and the facsimile signatures of its duly   authorized officers. DATED DD-MMM-YYYY President COUNTERSIGNED AND   REGISTERED: COMPUTERSHARE TRUST COMPANY, N.A. TRANSFER AGENT AND REGISTRAR,   April 25, 2007 CUSIP Holder ID Insurance Value Number of Shares DTC Certificate   Numbers 1234567890/1234567890 1234567890/1234567890 1234567890/1234567890   1234567890/1234567890 1234567890/1234567890 1234567890/1234567890 Total   Transaction XXXXXX XX X XXXXXXXXXX 1,000,000.00 123456 12345678   123456789012345 PO BOX 43004, Providence, RI 02940-3004 Num/No. Denom. Total   1 2 3 4 5 6 7 1 2 3 4 5 6 1 2 3 4 5 6 MR A SAMPLE DESIGNATION (IF ANY) ADD 1   ADD 2 ADD 3 ADD 4 Secretary By AUTHORIZED SIGNATURE 


    




 






 



 . QUANTERIX CORPORATION THE COMPANY WILL   FURNISH WITHOUT CHARGE TO EACH SHAREHOLDER WHO SO REQUESTS, A SUMMARY OF THE   POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE, PARTICIPATING, OPTIONAL OR   OTHER SPECIAL RIGHTS OF EACH CLASS OF STOCK OF THE COMPANY AND THE   QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH PREFERENCES AND RIGHTS,   AND THE VARIATIONS IN RIGHTS, PREFERENCES AND LIMITATIONS DETERMINED FOR EACH   SERIES, WHICH ARE FIXED BY THE CERTIFICATE OF INCORPORATION OF THE COMPANY,   AS AMENDED, AND THE RESOLUTIONS OF THE BOARD OF DIRECTORS OF THE COMPANY, AND   THE AUTHORITY OF THE BOARD OF DIRECTORS TO DETERMINE VARIATIONS FOR FUTURE   SERIES. SUCH REQUEST MAY BE MADE TO THE OFFICE OF THE SECRETARY OF THE   COMPANY OR TO THE TRANSFER AGENT. THE BOARD OF DIRECTORS MAY REQUIRE THE   OWNER OF A LOST OR DESTROYED STOCK CERTIFICATE, OR HIS LEGAL REPRESENTATIVES,   TO GIVE THE COMPANY A BOND TO INDEMNIFY IT AND ITS TRANSFER AGENTS AND   REGISTRARS AGAINST ANY CLAIM THAT MAY BE MADE AGAINST THEM ON ACCOUNT OF THE   ALLEGED LOSS OR DESTRUCTION OF ANY SUCH CERTIFICATE. The following   abbreviations, when used in the inscription on the face of this certificate,   shall be construed as though they were written out in full according to   applicable laws or regulations: TEN COM - as tenants in commonUNIF GIFT MIN   ACT - ............................................Custodian   ................................................ (Cust)(Minor) TEN ENT - as   tenants by the entiretiesunder Uniform Gifts to Minors   Act......................................................... (State) JT   TEN-as joint tenants with right of survivorshipUNIF TRF MIN ACT -   ............................................Custodian (until age   ................................) and not as tenants in common(Cust)   .............................under Uniform Transfers to Minors Act   ................... (Minor)(State) Additional abbreviations may also be used   though not in the above list. For value received, hereby sell, assign and   transfer unto PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF   ASSIGNEE (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING POSTAL ZIP   CODE, OF ASSIGNEE) Shares of the common stock represented by the within   Certificate, and do hereby irrevocably constitute and appoint Attorney to   transfer the said stock on the books of the within-named Company with full   power of substitution in the premises. Dated: 20 Signature: Signature(s)   Guaranteed: Medallion Guarantee Stamp THE SIGNATURE(S) SHOULD BE GUARANTEED   BY AN ELIGIBLE GUARANTOR INSTITUTION (Banks, Stockbrokers, Savings and Loan   Associations and Credit Unions) WITH MEMBERSHIP IN AN APPROVED SIGNATURE   GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15. Signature:   Notice: The signature to this assignment must correspond with the name as   written upon the face of the certificate, in every particular, without   alteration or enlargement, or any change whatever. The IRS requires that the   named transfer agent (“we”) report the cost basis of certain shares or units   acquired after January 1, 2011. If your shares or units are covered by the   legislation, and you requested to sell or transfer the shares or units using   a specific cost basis calculation method, then we have processed as you   requested. If you did not specify a cost basis calculation method, then we have   defaulted to the first in, first out (FIFO) method. Please consult your tax   advisor if you need additional information about cost basis. If you do not   keep in contact with the issuer or do not have any activity in your account   for the time period specified by state law, your property may become subject   to state unclaimed property laws and transferred to the appropriate state.