<PAGE>
                                                                    Exhibit 10.2

                                                               December 16, 2005

Katherine D. Crothall
c/o Animas Corporation
200 Lawrence Drive
West Chester, PA 19380

                    Re: Modification of Employment Agreement

Dear Dr. Crothall:

               As you know, Johnson & Johnson, a New Jersey corporation
("Parent"), Emerald Merger Sub, Inc., a Delaware corporation and wholly-owned
subsidiary of Parent ("Sub"), and Animas Corporation, a Delaware corporation
(the "Company"), propose to enter into an agreement and plan of merger (the
"Merger Agreement") that will result in the Company (or the surviving
corporation in the merger pursuant to the Merger Agreement (the "Merger"))
becoming wholly-owned by Parent. As a condition to the willingness of Parent and
Sub to enter into the Merger Agreement, Parent has requested that you enter into
this letter agreement setting forth certain agreements and modifications to your
rights and obligations under the Amended and Restated Employment Agreement dated
as of February 20, 2004 by and between the Company and you (the "Employment
Agreement"). Capitalized terms used but not defined herein have the meanings
given such terms under the Employment Agreement.

               Parent, the Company and you each agree as follows:

               1. Continuation of Employment. Following the consummation of the
Merger, and notwithstanding anything to the contrary in Sections 1.1 or 1.3 of
the Employment Agreement, you shall continue to be employed by the Company
solely as the President of the Company on the same terms and conditions as set
forth under the Employment Agreement (it being understood that the Company shall
cease to have a Chief Executive Officer following the consummation of the
Merger).

               2. Board Memberships. You agree that your rights under Section
1.4 of the Employment Agreement shall be subject to Parent's policy on outside
board memberships, civic and charitable activities, including obtaining any
required approval of Parent to continue any of your such existing memberships
and activities.

               3. Expiration of Employment Term. Upon the expiration of the
six-month anniversary of the consummation of the Merger (the "Six-Month
Anniversary"), the Employment Term will expire and you will cease to be an
employee of the Company (which shall be deemed a termination of employment
without Cause for purposes of the Employment Agreement).

               4. Modification of Severance Compensation Upon Certain
Terminations of Employment. Following termination of your employment upon the
expiration of the Six-Month Anniversary, or if the Company terminates your
employment without Cause prior to the Six-Month Anniversary, you shall be
entitled to the payments and benefits in accordance with Section 5.2 of the
Employment Agreement in accordance with the terms thereof (including your
obligation to execute the Release to receive any payments or benefits pursuant
to Section 5.2(b)), provided that the payment that would have otherwise been
paid in monthly installments under clause (i) of Section 5.2(b) of the
Employment Agreement shall be paid in a lump sum amount as soon as practicable
following your

<PAGE>

                                                                               2


termination of employment. If however, your employment terminates prior to the
Six-Month Anniversary as a result of a Constructive Termination Without Cause or
your voluntary resignation, you shall be entitled to receive the payments and
benefits as set forth in Section 5.2 of the Employment Agreement in accordance
with the terms thereof (including your obligation to execute the Release to
receive any payments or benefits pursuant to Section 5.2(b)), it being
understood that in such event the payments under clause (i) of Section 5.2(b) of
the Employment Agreement will be paid in eighteen monthly installments as
described therein. Notwithstanding the foregoing, you agree to waive your right
to any payments upon termination of employment under clause (iii) of Section
5.2(b) of the Employment Agreement. For the avoidance of doubt, no amounts shall
be payable to you under Sections 5.3, 5.4 or 5.5 of the Employment Agreement
upon your termination of employment following the consummation of the Merger,
except as provided under Paragraph 4 of this letter agreement.

               5. Modification of Confidentiality Covenant. You agree that the
third sentence in Section 2 of the Employment Agreement shall be amended in its
entirety to read as follows:

               "The Executive agrees that following the expiration of the
     Employment Term, she shall not disclose to any unauthorized person, firm or
     corporation or use for the Executive's own purposes any Confidential
     Information without the prior written consent of the Company, unless and to
     the extent that the aforementioned matters become generally known to and
     available for use by the public other than as a result of the Executive's
     acts or omissions in violation of this Agreement."

All references to "the Company" in Section 2 of the Employment Agreement shall
be deemed to refer to "the Company and Parent and their respective affiliates".

               6. Modification of Restrictive Covenants. You agree that Section
3 of the Employment Agreement shall be amended in its entirety to read as
follows:

               "3. Non-Competition; Non-Solicitation; Non-Hire; Work Product.

               3.1. Noncompetition. The Executive acknowledges that during her
     employment with the Company and its subsidiaries she has become familiar
     with the Company's trade secrets and with other Confidential Information
     concerning the Company and its predecessors and their respective
     affiliates, and that during the period of employment with the Company and
     during any post-employment relationship she will become familiar with trade
     secrets and other Confidential Information of Company, Johnson & Johnson, a
     New Jersey corporation ("Parent"), and their respective affiliates, and
     that her services have been and shall be of special, unique and
     extraordinary value to Parent, the Company and their respective affiliates.
     The Executive understands that the Company and Parent shall be entitled to
     protect and preserve the going concern value of the Company to the extent
     permitted by law and that the Company and Parent would not have entered
     into the Merger Agreement (as defined in the letter agreement dated
     December 16, 2005, between the Executive and the Company and Parent (the
     "Letter Agreement") without the Executive's agreement to the covenants
     contained in this Section 3.1 and in Sections 3.2 and 3.3 hereof. The
     Executive further acknowledges that while her compliance with the covenants
     contained in this Section 3.1 and in Sections 3.2 and 3.3 hereof will
     prevent the Executive from earning a livelihood in the field of diabetes,
     the Executive will have other opportunities to earn a livelihood outside of
     the field of diabetes, and in addition the Executive agrees that the
     covenants contained in this Section 3.1 and in Sections 3.2 and 3.3 hereof
     are reasonable and appropriate in light of the consideration to be paid by
     Parent for the shares of Company common stock the

<PAGE>

                                                                               3


     Executive in accordance with the transactions contemplated by the Merger
     Agreement. The Executive acknowledges and agrees that the purpose of this
     Section 3.1 and Section 3.2 are to exclude her, except as expressly
     provided below, from the field of diabetes generally and specifically from
     competing with the businesses of the Company and any of Parent's franchises
     now or in the future relating to the research, development, manufacturing,
     marketing and sale of test strips, pumps and meters for the period
     described below. Therefore, the Executive agrees that during the five-year
     period immediately following the consummation of the Merger (as defined in
     the Letter Agreement), she shall not, directly or indirectly, in any
     manner, alone or in association with any person:

               (a) compete with Parent, the Company or any of their respective
          affiliates in the testing, monitoring, diagnosing, prognostication,
          treatment, management or cure of diabetes in diabetics, but not
          diseases resulting from diabetes, and the testing, monitoring,
          prognostication, management or control of glucose concentrations in
          nondiabetics) (the "Diabetes Field"); or

               (b) engage in any activity in the Diabetes Field (including,
          without limitation, researching, developing, manufacturing, marketing,
          selling, distributing, or licensing (to or from third parties) of
          technology or products or providing services for the testing,
          monitoring, diagnosing, prognostication, treatment, management or cure
          of diabetes and diabetes related symptoms and conditions); or

               (c) actively participate in, control, manage, own any interest in
          or share in the earnings of, finance or invest in the capital stock of
          any person engaged in any activity in the Diabetes Field or consult
          with any person on matters in the Diabetes Field, except that the
          Executive may (i) acquire up to 2% of the equity or voting interest in
          an entity engaged in activities in the Diabetes Field, only so long as
          the Executive is not actively involved, whether directly or
          indirectly, in the management of such entity or (ii) be employed by or
          a partner in an investment fund that has investments in the Diabetes
          Field, only so long as the Executive is not actively involved, whether
          directly or indirectly, in the management or direction of any company
          in the portfolio of such fund where such company is in the Diabetes
          Field.

     For purposes of this Agreement, being "actively involved" includes, without
     limitation, acting directly or indirectly as an officer, director,
     proprietor, employee, partner, lender, or, on matters in the Diabetes
     Field, as a consultant, advisor, agent or representative.

               3.2. Nonsolicitation; Nonhiring.

               (a) The Executive agrees that during the three-year period
     immediately following the consummation of the Merger, she shall not, in any
     manner, directly or indirectly (i) induce any person who, within the prior
     two-year period, has been an employee of or consultant to Parent, the
     Company or any of their respective affiliates to leave the employ of or
     cease rendering services to Parent, the Company or any of their respective
     affiliates, (ii) except in response to a good faith request by a Person
     that is not a competitor of Parent, the Company or any of their affiliates
     in the Diabetes Field for a recommendation regarding the employment
     qualifications of such employee or consultant, recommend to any other
     Person that he or she employ any such employee or

<PAGE>

                                                                               4


     consultant or (iii) hire (whether as an employee, consultant or in any
     other capacity) any such employee or consultant, except that the Executive
     shall not be precluded from hiring any general business, regulatory or
     legal consultant or any consultant who has not provided consulting services
     to Parent, the Company or any of their respective affiliates in the
     Diabetes Field during the prior one-year period.

               (b) The Executive agrees that during the three-year period
     immediately following the consummation of the Merger, she shall not, in any
     manner, directly or indirectly, (i) solicit by mail, by telephone, by
     personal meeting or by any other means, either directly or indirectly, any
     customer or supplier of Parent, the Company or any of their respective
     affiliates to transact business in the Diabetes Field with a business or
     enterprise that competes with Parent, the Company or any of their
     respective affiliates in the Diabetes Field or reduce or refrain from doing
     any business with Parent, the Company or any of their respective
     affiliates, or (ii) disparage (including by relative comparison) Parent or
     the Company or any of their respective affiliates or any products or
     activities of any of the foregoing in the Diabetes Field.

               3.3. Notification of Subsequent Employer. The Executive hereby
     agrees that prior to accepting employment with any other person or entity
     during the Employment Term or any period thereafter during which the
     Executive remains subject to any of the covenants set forth in Sections 3.1
     or 3.2, the Executive will provide such prospective employer with written
     notice of the provisions of this Agreement, with a copy of such notice
     delivered simultaneously to the Company and Parent.

               3.4. Work Product.

               (a) Any reports, data, presentations, inventions, documents and
     computer models made or conceived, or notebooks or other recording methods
     kept, by the Executive (collectively, "Work Products") in the course of the
     Executive's performance of services for the Company or Parent or their
     respective affiliates and any proprietary rights relating thereto
     (including patents and trademarks and applications therefor) shall be the
     property of the Company and Parent. The Executive agrees to assign, and
     does hereby assign, to the Company and Parent all right, title and interest
     of whatsoever kind and nature in and to all such reports, data,
     presentations, inventions, documents, computer models and ideas and related
     proprietary rights. The Executive shall execute, acknowledge, and deliver
     to the Company and Parent all such further papers as may be necessary to
     enable the Company and Parent to own, register, publish or protect said
     deliverables and reports, data, presentations, inventions, documents,
     computer models and ideas and related proprietary rights in any and all
     countries and to vest title to said reports, data, documents, computer
     models and ideas and related proprietary rights in the Company, Parent or
     their nominees, and their successors or assigns. The Executive shall render
     all such assistance as the Company and Parent may reasonably require in any
     proceeding or litigation involving said inventions, improvements,
     presentations, inventions, trademarks or ideas. The Executive, as part of
     the services to be performed hereunder, shall keep written notebook records
     of its work, properly witnessed for use as invention records, and shall
     submit such records to the Company and Parent when requested or at the
     termination of the services contemplated hereby.

               (b) The parties agree that the copyright and all other rights in
     and to all copyrightable work created by the Executive in the course of the
     Executive's

<PAGE>

                                                                               5


     performance of services shall belong completely and in all respects to
     Company and Parent and that the Executive shall retain no rights in or to
     same. The parties further expressly agree that the aforementioned work will
     be considered and deemed as work made for hire for the benefit and
     exclusive ownership of Company and Parent to the fullest extent permitted
     by law, provided, however, that if said work shall not be legally qualified
     as a work made for hire, the Executive agrees to assign, and does hereby so
     assign to Company, all rights, title and interest in and to said work,
     including, but not limited to, the copyright therein. The Executive agrees
     to furnish and execute such additional documents as Company may require to
     establish Company's ownership of the copyright in the work including,
     without limitation, such assignments of the copyright herein throughout the
     world as Company may deem appropriate."

               7. Modification of Equitable Relief. You agree that Section 4.2
of the Employment Agreement shall be amended in its entirety to read as follows:

               "The Executive acknowledges that a violation on the Executive's
     part of any of the covenants contained in Section 2, 3.1 or 3.2 hereof
     would cause immeasurable and irreparable harm to the Company and Parent in
     an amount that would be material but not readily ascertainable, and that
     any remedy at law (including the payment of damages) would be inadequate.
     Accordingly, and notwithstanding the provisions of Section 8, the Executive
     agrees that the Company and Parent shall be entitled (without the necessity
     of showing economic loss or other actual damage) to injunctive relief and
     the grant of a conservative order in any court of competent jurisdiction
     for any actual or threatened violation of any such covenant in addition to
     any other remedies it may have. The Executive agrees that in the event that
     any arbitrator or court of competent jurisdiction shall finally hold that
     any provision of Section 2, 3.1 or 3.2 shall hereof is void or constitutes
     an unreasonable restriction against the Executive, the provisions of such
     Section 2, 3.1 or 3.2 shall not be rendered void but shall be deemed to be
     modified to the minimum extent necessary to remain in force and effect for
     the greatest period and to such extent as such arbitrator or court may
     determine constitutes a reasonable restriction under the circumstances."

               8. Future Potential Arrangements. The Company and you will
consider entering into a consulting arrangement commencing upon the expiration
of the Six-Month Anniversary, for a period not in excess of six months on
mutually agreeable terms. The foregoing shall not preclude the Company and you
from considering a continuation of your relationship as an employee of the
Company after the expiration of the Six-Month Anniversary on mutually agreeable
terms.

               9. Full Force and Effect. For the avoidance of doubt, the
Employment Agreement, as modified and amended by this letter agreement, shall
remain in full force and effect following the consummation of the Merger.

               10. Governing Law. This letter agreement will be governed by,
construed and interpreted in accordance with the laws of the State of
Pennsylvania, without regard to its principles of conflicts of laws.

               11. Entire Agreement. This letter agreement contains the entire
agreement among you, Parent and the Company concerning the subject matter hereof
and supersedes all prior agreements, understandings, discussions, negotiations
and undertakings, whether written or oral, among you, Parent and the Company
with respect hereto. This letter agreement may not be modified or amended except
by a writing signed by each of the parties hereto.

<PAGE>

                                                                               6


               12. Successors and Assigns. This letter agreement shall be
binding on (a) you and your estate and legal representatives and (b) the
Company, Parent, and their respective successors and assigns. The Company and
Parent shall require any successor (whether direct or indirect, by purchase,
merger, consolidation or otherwise) to all or substantially all of the business
and/or assets of the Company or the Parent, as the case may be, expressly to
assume and agree to perform this letter agreement in the same manner and to the
same extent that the Company and Parent would have been required to perform it
if no such succession had taken place.

               13. Counterparts. This letter agreement may be executed in two or
more counterparts (including via facsimile), each of which shall be deemed an
original but all of which together shall be considered one and the same
agreement.

<PAGE>

               You acknowledge that your agreement to the terms and conditions
of this letter agreement is in consideration of the benefits provided under
Paragraphs 1 and 4 of this letter agreement and is an inducement to and a
condition of Parent's and Sub's willingness to enter into the Merger Agreement.
You acknowledge and agree that this letter agreement constitutes an amendment to
the Employment Agreement. This letter agreement will be void and of no further
force and effect if the Merger Agreement is terminated prior to the consummation
of the Merger (it being understood that Parent shall have no liabilities or
obligations hereunder unless and until the Merger is consummated).

                                        Very truly yours,

                                        JOHNSON & JOHNSON


                                        By: /s/ John A. Papa
                                            ------------------------------------
                                        Name: John A. Papa
                                        Title: Treasurer

<PAGE>

                                        ANIMAS CORPORATION


                                        By: /s/ Katherine D. Crothall
                                            ------------------------------------
                                        Name: Katherine D. Crothall
                                        Title: President and CEO


Agreed and Accepted:


/s/ Katherine D. Crothall
-------------------------------------
Katherine D. Crothall