Restoring the sense of touch

Abstract

Amputation of damaged tissue is one of the oldest surgical techniques, reaching prevalence in the 16th century (1). Improved emergency medicine has allowed more individuals to survive traumatic injuries as amputees, but prosthetic limbs remain the only means to restore any degree of function to these patients. Inadequate tactile feedback is a leading shortcoming of prosthetic limbs, but for artificial hands, just a few sensors that relay grasp pressure back to the user can provide the functionality needed to enable delicate tasks (2). In addition to improved motor control, sensory stimulation could alleviate phantom limb pain, which affects ~80% of amputees (2). On page 314 of this issue, Tee et al. (3) report a Digital Tactile System (“DiTact”) based on a low-power flexible organic transistor circuit that transduces pressure stimuli into oscillating signals like those generated by skin mechanoreceptors. Mammalian skin is a multilayered viscoelastic material that can stretch up to ~125% from its resting dimensions without any apparent loss in sensitivity to external stimuli such as pressure or temperature. Replicating skin mechanical and functional properties remains an elusive engineering challenge. Meanwhile, the rapidly expanding field of flexible electronics has made substantial strides, and complex circuits can now be produced on soft substrates. Advances in microcontact printing, inkjet deposition, and organic electronics have delivered stretchable and flexible, wearable, and even epidermal sensors (4–6).