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                                                                     EXHIBIT 4.1

                                 FORM OF WARRANT


                           ACACIA RESEARCH CORPORATION

               WARRANTS FOR THE PURCHASE OF SHARES OF COMMON STOCK

NO. W-[   ]                                                         [   ] SHARES


         THIS CERTIFIES that, for value received, Acacia Research Corporation, a
Delaware corporation (the "Company"), upon the surrender of this Warrant to the
Company at the address specified herein, at any time during the Exercise Period
(as defined below) will upon receipt of the Exercise Price (as defined below),
sell and deliver to [     ] (the "Holder") up to the number of duly authorized,
validly issued and fully paid and nonassessable shares of common stock of the
Company designated as Acacia Research--CombiMatrix Common Stock, par value
$0.001 per share, set forth above. The term "Common Stock" shall mean the
aforementioned common stock of the Company together with any other equity
securities that may be issued by the Company in connection therewith or in
substitution therefor, as provided herein, that is not limited as to final sum
or percentage in respect of the rights of the holders thereof to participate in
dividends or in distribution of assets upon the voluntary or involuntary
liquidation, dissolution or winding up of the Company. The "Exercise Period"
shall begin on September 21, 2005 and shall end on September 21, 2010 During the
Exercise Period, the Holder may purchase such number of shares of Common Stock
at a purchase price per share equal to $2.40 as appropriately adjusted pursuant
to Section G hereof (the "Exercise Price"). Following the exercise period, the
Holder shall have no right to purchase all or any portion of the Warrant Shares.

         The number of shares of Common Stock to be received upon the exercise
of this Warrant and the price to be paid for a share of Common Stock are subject
to adjustment from time to time as hereinafter set forth. The shares of Common
Stock deliverable upon such exercise, as adjusted from time to time, are
hereinafter sometimes referred to as "Warrant Shares."

         SECTION A. EXERCISE OF WARRANT. This Warrant may be exercised in whole
or in part, at any time or from time to time, during the Exercise Period by
presentation and surrender hereof to the Company at its principal office at, 500
Newport Center Drive, 7th Floor, Newport Beach, California 92660 (or at such
other address as the Company or its agent may hereafter designate in writing to
the Holder), or at the office of its warrant agent, with the Notice of Exercise
Form contained herein duly executed and accompanied by a wire transfer of
immediately available funds, cash or a certified or official bank check drawn to
the order of "Acacia Research Corporation" in the amount of the Exercise Price
multiplied by the number of Warrant Shares specified in such form. If this
Warrant should be exercised in part only, the Company shall, upon surrender of
this Warrant, promptly execute and deliver a new Warrant evidencing the rights
of the Holder thereof to purchase the balance of the Warrant Shares purchasable
hereunder. Upon receipt by the Company during the Exercise Period of this
Warrant and such Notice of Exercise Form, in proper form for exercise, together
with proper payment of the Exercise Price, at such office, or by the warrant
agent of the Company at its office, the Holder shall be deemed to be the holder


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of record of the number of Warrant Shares specified in such form; PROVIDED,
HOWEVER, that if the date of such receipt by the Company or its agent is a date
on which the stock transfer books of the Company are closed, such person shall
be deemed to have become the record holder of such shares on, and such
certificate shall be dated, the next succeeding business day on which the stock
transfer books of the Company are open. The Company shall pay any and all
documentary, stamp or similar issue or transfer taxes payable in respect of the
issue or delivery of such Warrant Shares. Any new or substitute Warrant issued
under this Section A or any other provision of this Warrant shall be dated the
date of this Warrant. Upon exercise of this Warrant, the Company or its warrant
agent shall, within 3 business days, cause to be issued and shall promptly
deliver upon written order of the Holder of this Warrant, and in such name or
names as such Holder may designate, a certificate or certificates for the
Warrant Shares, which Warrant Shares shall be issued unlegended and free of any
resale restrictions, except as otherwise provided herein. If the Company's
transfer agent is a participant in the DTC FAST system, then such Warrant Shares
shall be delivered electronically by crediting the broker account designated by
the Holder pursuant to the DWAC system. If the Holder elects to exercise all or
any part of this Warrant when there is no effective registration statement
permitting the sale of the Warrant Shares by the Company to the Holder, then
this Warrant may also be exercised at such time by means of a "cashless
exercise" in which the Holder shall be entitled to receive a certificate for the
number of Warrant Shares equal to the quotient obtained by dividing [(A-B) (X)]
by (A), where:

                  (A) =    the closing bid price on the business day immediately
                           preceding the date of such election as reported by
                           Bloomberg, L.P.;

                  (B) =    the Exercise Price of this Warrant, as adjusted; and

                  (X) =    the number of Warrant Shares issuable upon exercise
                           of this Warrant in accordance with the terms of this
                           Warrant by means of a cash exercise rather than a
                           cashless exercise.

If the Company fails to deliver to the Holder a certificate or certificates
representing the Warrant Shares pursuant to this Section A by the 3rd trading
day after exercise hereof, then the Holder will have the right to rescind such
exercise. In addition to any other rights available to the Holder, if the
Company fails to cause its transfer agent to transmit to the Holder a
certificate or certificates representing the Warrant Shares pursuant to an
exercise on or before the 3rd trading day following a Warrant exercise, and if
after such date the Holder is required by its broker to purchase (in an open
market transaction or otherwise) shares of Common Stock to deliver in
satisfaction of a sale by the Holder of the Warrant Shares which the Holder
anticipated receiving upon such exercise (a "Buy-In"), then the Company shall
(1) pay in cash to the Holder the amount by which (x) the Holder's total
purchase price (including brokerage commissions, if any) for the shares of
Common Stock so purchased exceeds (y) the amount obtained by multiplying (A) the
number of Warrant Shares that the Company was required to deliver to the Holder
in connection with the exercise at issue by (B) the price at which the sell
order giving rise to such purchase obligation was executed, and (2) at the


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option of the Holder, either reinstate the portion of the Warrant and equivalent
number of Warrant Shares for which such exercise was not honored or deliver to
the Holder the number of shares of Common Stock that would have been issued had
the Company timely complied with its exercise and delivery obligations
hereunder. For example, if the Holder purchases Common Stock having a total
purchase price of $11,000 to cover a Buy-In with respect to an attempted
exercise of shares of Common Stock with an aggregate sale price giving rise to
such purchase obligation of $10,000, under clause (1) of the immediately
preceding sentence the Company shall be required to pay the Holder $1,000. The
Holder shall provide the Company written notice indicating the amounts payable
to the Holder in respect of the Buy-In, together with applicable confirmations
and other evidence reasonably requested by the Company. Nothing herein shall
limit a Holder's right to pursue any other remedies available to it hereunder,
at law or in equity including, without limitation, a decree of specific
performance and/or injunctive relief with respect to the Company's failure to
timely deliver certificates representing shares of Common Stock upon exercise of
the Warrant as required pursuant to the terms hereof.

                  Notwithstanding anything herein to the contrary, the Holder
shall not have the right to exercise any portion of this Warrant, pursuant to
Section A or otherwise, to the extent that after giving effect to such issuance
after exercise, the Holder (together with the Holder's affiliates), as set forth
on the applicable Notice of Exercise, would beneficially own in excess of 9.99%
of the number of shares of the Common Stock outstanding immediately after giving
effect to such issuance. For purposes of the foregoing sentence, the number of
shares of Common Stock beneficially owned by the Holder and its affiliates shall
include the number of shares of Common Stock issuable upon exercise of this
Warrant with respect to which the determination of such sentence is being made,
but shall exclude the number of shares of Common Stock which would be issuable
upon (A) exercise of the remaining, nonexercised portion of this Warrant
beneficially owned by the Holder or any of its affiliates and (B) exercise or
conversion of the unexercised or nonconverted portion of any other securities of
the Company (including, without limitation, any other Warrants) subject to a
limitation on conversion or exercise analogous to the limitation contained
herein beneficially owned by the Holder or any of its affiliates. Except as set
forth in the preceding sentence, for purposes of this provision, beneficial
ownership shall be calculated in accordance with Section 13(d) of the Exchange
Act. To the extent that the limitation contained in this provision applies, the
determination of whether this Warrant is exercisable (in relation to other
securities owned by the Holder) and of which a portion of this Warrant is
exercisable shall be in the sole discretion of such Holder, and the submission
of a Notice of Exercise shall be deemed to be such Holder's determination of
whether this Warrant is exercisable (in relation to other securities owned by
such Holder) and of which portion of this Warrant is exercisable, in each case
subject to such aggregate percentage limitation, and the Company shall have no
obligation to verify or confirm the accuracy of such determination. For purposes
of this provision, in determining the number of outstanding shares of Common
Stock, the Holder may rely on the number of outstanding shares of Common Stock
as reflected in (x) the Company's most recent Form 10-Q or Form 10-K, as the
case may be, (y) a more recent public announcement by the Company or (z) any
other notice by the Company or the Company's transfer agent setting forth the
number of shares of Common Stock outstanding. In any case, the number of
outstanding shares of Common Stock shall be determined after giving effect to
the conversion or exercise of securities of the Company, including this Warrant,
by the Holder or its affiliates since the date as of which such number of
outstanding shares of Common Stock was reported.


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         SECTION B. WARRANT REGISTER. This Warrant will be registered in a
register (the "Warrant Register") to be maintained by the Company or its agent
at its principal office in the name of the recordholder to whom it has been
distributed. The Company may deem and treat the registered holder of this
Warrant as the absolute owner thereof (notwithstanding any notation of ownership
or other writing hereon made by anyone), for the purpose of any exercise thereof
or any distribution to the holder thereof and for all other purposes, and the
Company shall not be affected by any notice to the contrary.

         SECTION C. RESERVATION OF SHARES. The Company hereby agrees that at all
times there shall be reserved for issuance and delivery upon exercise of this
Warrant all shares of its Common Stock or other shares of capital stock of the
Company from time to time issuable upon exercise of this Warrant. All such
shares shall be duly authorized and, when issued upon such exercise in
accordance with the terms of this Warrant, shall be validly issued, fully paid
and nonassessable, free and clear of all liens, security interests, charges and
other encumbrances or restrictions on sale and free and clear of all preemptive
rights.

         SECTION D. TRANSFER OF WARRANT. Subject to compliance with applicable
federal and state securities laws, this Warrant and all rights hereunder are
transferable, in whole or in part, without charge to the Holder hereof (except
for transfer taxes), upon surrender of this Warrant with the Form of Assignment
attached hereto duly completed and properly endorsed.

         SECTION E. LOST, MUTILATED OR MISSING WARRANT. Upon receipt by the
Company of evidence reasonably satisfactory to it of the loss, theft,
destruction or mutilation of this Warrant, and (in the case of loss, theft or
destruction) of reasonably satisfactory indemnification, and upon surrender and
cancellation of this Warrant, if mutilated, the Company, at its expense, shall
execute and deliver a new Warrant of like tenor and date.

         SECTION F. RIGHTS OF THE HOLDER. Subject to applicable law, the Holder
shall not, by virtue hereof, be entitled to any voting or other rights
including, without limitation, notice of meetings, or other actions or receipt
of dividends or subject to any obligation or liability of a shareholder in the
Company, either at law or equity, and the rights of the Holder are limited to
those expressed in this Warrant.

         SECTION G. ADJUSTMENTS. The Exercise Price and the number of shares
purchasable hereunder are subject to adjustment from time to time as follows:

                  1. STOCK DIVIDEND, SPLIT OR SUBDIVISION OF SHARES. If the
         number of shares of Common Stock outstanding at any time after the date
         hereof is increased by a stock dividend payable to all holders of
         Common Stock in shares of Common Stock or by a subdivision or split-up
         of shares of Common Stock, then, following the record date fixed for
         the determination of holders of Common Stock entitled to receive such
         stock dividend, subdivision or split-up, the Exercise Price shall be
         appropriately decreased and the number of shares of Common Stock
         issuable on exercise of each Warrant shall be increased in proportion
         to such increase in outstanding shares.


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                  2. COMBINATION OF SHARES. If, at any time after the date
         hereof, the number of shares of Common Stock outstanding is decreased
         by a combination or consolidation of the outstanding shares of Common
         Stock, by reclassification, reverse stock split or otherwise, then,
         following the record date for such combination, the Exercise Price
         shall be appropriately increased and the number of shares of Common
         Stock issuable on exercise of each Warrant shall be decreased in
         proportion to such decrease in outstanding shares.

                  3. CALCULATIONS. All calculations under this Section shall be
         made to the nearest one-tenth of a cent ($.001), or to the nearest
         one-tenth of a share, as the case may be.

                  4. MERGER AND CONSOLIDATION. If at any time there is a capital
         reorganization or reclassification of shares of Common Stock, or a
         merger or consolidation of the Company with or into another corporation
         where the Company is not the surviving corporation, or the sale of all
         or substantially all of the Company's properties and assets to any
         other person, then as part of such reorganization, merger,
         consolidation or sale, lawful provision shall be made so that the
         Holder shall thereafter be entitled to receive upon exercise of its
         rights to purchase Common Stock, the number of shares of Common Stock,
         cash, property or shares of the successor corporation resulting from
         such merger or consolidation, to which a holder of Common Stock,
         deliverable upon exercise of the rights to purchase Common Stock
         hereunder, would have been entitled in such capital reorganization,
         merger or consolidation or sale if the right to purchase such Common
         Stock hereunder had been exercised immediately prior to such capital
         reorganization, merger, consolidation or sale. In any such event,
         appropriate adjustment shall be made in the application of the
         provisions of this Warrant with respect to the rights and interests of
         the Holder after such capital reorganization, merger, consolidation or
         sale so that the provisions of this Warrant (including Exercise Price
         and the number of shares of Common Stock purchasable pursuant to the
         terms and conditions of this Warrant) shall be applicable after that
         event as near as reasonably may be, in relation to any shares
         deliverable upon the exercise of the Holder's rights to purchase Common
         Stock pursuant to this Warrant.

                  5. CERTIFICATE AS TO ADJUSTMENTS. Upon the occurrence of each
         adjustment or readjustment pursuant to this Section G, the Company, at
         its own expense, shall promptly compute such adjustment or readjustment
         in accordance with the terms hereof and furnish to each Holder a
         certificate setting forth such adjustment or readjustment and showing
         in detail the facts upon which such adjustment or readjustment is
         based. The Company shall, upon the written request, at any time, of any
         such Holder, furnish or cause to be furnished to such Holder no more
         than one certificate setting forth: (a) such adjustments and
         readjustments; (b) the Exercise Price at the time in effect; and (c)
         the number of shares and the amount, if any of other property that at
         the time would be received upon the exercise of the Warrant.


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         SECTION H. FRACTIONAL SHARES. No fractional shares of the Company's
Common Stock will be issued in connection with any purchase hereunder but in
lieu of such fractional shares the Company shall make a cash refund therefor
equal in amount to the product of the applicable fraction multiplied by the
Exercise Price paid by the Holder for one Warrant Share upon such exercise.

         SECTION I. NOTICES OF CERTAIN EVENTS. In the event:

                  1. the Company authorizes the issuance to all holders of its
         Common Stock of rights or warrants to subscribe for or purchase shares
         of its Common Stock or of any other subscription rights or warrants; or

                  2. the Company authorizes the distribution to all holders of
         its Common Stock of evidences of its indebtedness or assets (other than
         cash dividends or distributions except extraordinary cash dividends or
         distributions); or

                  3. of any capital reorganization or reclassification of the
         Common Stock (other than a subdivision or combination of the
         outstanding Common Stock and other than a change in par value of the
         Common Stock) or of any consolidation or merger to which the Company is
         a party or of the conveyance or transfer of all or substantially all of
         the properties and assets of the Company; or

                  4. of the voluntary or involuntary dissolution, liquidation or
         winding-up of the Company; or

                  5. any other actions would require an adjustment under Section
         G hereof;

then the Company will cause to be mailed to the Holder, at least 5 days before
the applicable record or effective date hereinafter specified, a notice stating
(A) the date as of which the holders of Common Stock of record entitled to
receive any such rights, warrants or distributions are to be determined, or (B)
the date on which any such consolidation, merger, conveyance, transfer,
dissolution, liquidation or winding-up is expected to become effective, and the
date as of which it is expected that holders of Common Stock of record will be
entitled to exchange their shares of Common Stock for securities or other
property, if any, deliverable upon such reorganization, reclassification,
consolidation, merger, conveyance, transfer, dissolution, liquidation or
winding-up.

         SECTION J. LISTING ON SECURITIES EXCHANGES. The Company will list on
the Nasdaq National Market and each national securities exchange on which any
Common Stock may at any time be listed all shares of Common Stock from time to
time issuable upon the exercise of this Warrant, subject to official notice of
issuance upon the exercise of this Warrant, and will maintain such listing so
long as any other shares of its Common Stock are so listed; and the Company
shall so list on the Nasdaq National Market and each national securities
exchange, and shall maintain such listing of, any other shares of capital stock
of the Company issuable upon the exercise of this Warrant if and so long as any
shares of capital stock of the same class are listed on the Nasdaq National
Market and such national securities exchange by the Company. Any such listing
will be at the Company's expense.


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         SECTION K. SUCCESSORS. All the provisions of this Warrant by or for the
benefit of the Company shall bind and inure to the benefit of its respective
successors and assigns.

         SECTION L. HEADINGS. The headings of sections of this Warrant have been
inserted for convenience of reference only, are not to be considered a part
hereof and shall in no way modify or restrict any of the terms or provisions
hereof.

         SECTION M. AMENDMENTS. The terms and provisions of this Warrant may not
be modified or amended, or any provisions hereof waived, temporarily or
permanently, except by written consent of the Company and the Holder hereof.

         SECTION N. NOTICES. Unless otherwise provided in this Warrant, all
notices, requests, consents and other communications hereunder shall be in
writing, shall be sent by U.S. Mail or a nationally recognized overnight express
courier postage prepaid, and shall be deemed given one day after being so sent,
or if delivered by hand shall be deemed given on the date of such delivery to
such party, or if sent to such party (in the case of a Holder) at its address in
the Warrant Register that will be maintained by the Company or its agent in
accordance with Section B hereof or (in the case of the Company) at its address
set forth above, Attention: Chief Financial Officer, or to such other address as
is designated by written notice, similarly given to each other party hereto.

         SECTION O. GOVERNING LAW. This Warrant shall be deemed to be a contract
made under the laws of the State of New York and for all purposes shall be
construed in accordance with the laws of said State as applied to contracts made
and to be performed in New York between New York residents.


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         IN WITNESS WHEREOF, the Company has duly caused this Warrant to be
signed and attested by its duly authorized officer and to be dated as of
September 21, 2005.


                                   ACACIA RESEARCH CORPORATION


                                   By:________________________________
                                   Name:
                                   Title: President and Chief Executive Officer


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                               NOTICE OF EXERCISE


                                                 Date: ___________________, 20__


         The undersigned hereby irrevocably elects to exercise this Warrant to
purchase ____ shares of Common Stock and hereby makes payment of $____________
in payment of the aggregate exercise price in full thereof, or if permitted by
the terms of the Warrant, ____________ elects cashless exercise as follows:

         Closing bid price:
         Exercise Price:
         Number of Warrant Shares to be issued:.


         Warrant Shares shall be issued in the name of and delivered to the
following address or DWAC Account:



                                            ___________________________________
                                            [Holder's Name]


                                            By:________________________________
                                            Name:
                                            Title:


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                               FORM OF ASSIGNMENT

           [To be completed and signed only upon transfer of Warrant]

FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers unto the
right represented by the within Warrant to purchase shares of Common Stock to
which the within Warrant relates and appoints attorney to transfer said right on
the books of the Company with full power of substitution in the premises.


Dated: _____________ ,_____

                                    __________________________________________
                                    (Signature must conform in all respects to
                                    name of holder as specified on the face of
                                    the Warrant)

                                    __________________________________________
                                    Address of Transferee

                                    __________________________________________

                                    __________________________________________


In the presence of:

__________________________________________


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