A device for simultaneous actuation and sensing comprising: - an actuator comprising: - an actuator material capable of deforming upon application of a control signal to it, the actuator having a mechanical resonance frequency and corresponding mechanical anti-resonance frequency; - an arrangement for applying a first control signal, for use in actuation, to at least a first part of the actuator material; - an electrode arrangement for applying an electrical second control signal, for use in sensing, to at least a second part of the actuator material; - a controller configured for: - providing the first control signal to the arrangement; - providing the electrical second control signal to the electrode arrangement, wherein the controller is further configured for: - providing the first control signal and the electrical second control signal such that they can be applied to the respective parts of the actuator material simultaneously; characterised in that the controller is further configured for - providing the electrical second control signal as an alternating signal having a sensing frequency that is harmonic with either the mechanical resonance frequency or the mechanical anti-resonance frequency. - an actuator comprising: - an actuator material capable of deforming upon application of a control signal to it, the actuator having a mechanical resonance frequency and corresponding mechanical anti-resonance frequency; - an arrangement for applying a first control signal, for use in actuation, to at least a first part of the actuator material; - an electrode arrangement for applying an electrical second control signal, for use in sensing, to at least a second part of the actuator material; - an actuator material capable of deforming upon application of a control signal to it, the actuator having a mechanical resonance frequency and corresponding mechanical anti-resonance frequency; - an arrangement for applying a first control signal, for use in actuation, to at least a first part of the actuator material; - an electrode arrangement for applying an electrical second control signal, for use in sensing, to at least a second part of the actuator material; - a controller configured for: - providing the first control signal to the arrangement; - providing the electrical second control signal to the electrode arrangement, wherein the controller is further configured for: - providing the first control signal and the electrical second control signal such that they can be applied to the respective parts of the actuator material simultaneously; characterised in that the controller is further configured for - providing the electrical second control signal as an alternating signal having a sensing frequency that is harmonic with either the mechanical resonance frequency or the mechanical anti-resonance frequency. - providing the first control signal to the arrangement; - providing the electrical second control signal to the electrode arrangement, - providing the first control signal and the electrical second control signal such that they can be applied to the respective parts of the actuator material simultaneously; characterised in that the controller is further configured for - providing the electrical second control signal as an alternating signal having a sensing frequency that is harmonic with either the mechanical resonance frequency or the mechanical anti-resonance frequency. <EOS>