  The actin droplet machine is a computer model of a three-dimensional network
of actin bundles developed in a droplet of a physiological solution, which
implements mappings of sets of binary strings. The actin bundle network is
conductive to travelling excitations, i.e. impulses. The machine is interfaced
with an arbitrary selected set of k electrodes through which stimuli, binary
strings of length k represented by impulses generated on the electrodes, are
applied and responses are recorded. The responses are recorded in a form of
impulses and then converted to binary strings. The machine's state is a binary
string of length k: if there is an impulse recorded on the $i$th electrode,
there is a `1' in the i-th position of the string, and `0' otherwise. We
present a design of the machine and analyse its state transition graphs. We
envisage that actin droplet machines could form an elementary processor of
future massive parallel computers made from biopolymers.
