3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes (‘rapid prototyping’) before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term ‘carbomorph’ and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes.

Air-coupled capacitance transducers have been manufactured using anisotropically etched silicon backplates and commercially available dielectric films (Kapton and Mylar). The small backplate pits which result from etching, provide well ordered and highly uniform air layers between the backplate surface and thin dielectric film. Such uniformity allows the transducers to be manufactured with reproducible characteristics (a property difficult to achieve through conventional manufacturing). Impulse response studies in generation and detection, have indicated well-damped, wideband behavior, with bandwidths extending from <100 kHz to 2.3 MHz (at the -6 dB points). These bandwidths are investigated as a function of excitation pulse width, applied bias potential, and dielectric film thickness. An estimate of detection sensitivity is also provided by comparison with a calibrated laser interferometer.<>

Quantitative experimental measurements have been made in the study of thermoelastic generation of elastic waves in a metal by unfocused laser radiation. A calibrated wide‐band detection system, incorporating a capacitance transducer, has enabled acoustic waveforms to be recorded with a minimum of distortion. From these measurements, a theoretical model has been developed. The transfer function of the metal block has been deconvoluted to give the acoustic source function, which was modeled as a rapidly expanding point volume of material. The thermoelastic source generated longitudinal (L) and (S) waves, but the latter predominated at the epicenter, where, in experiments presented here, both wave amplitudes L and S were proportional to the total absorbed energy in the laser pulse.

The generation of acoustic waves in metals by pulsed laser irradiation over a wide range of material conditions has been studied. Capacitance transducers have been used to obtain quantitative measurements of the amplitude of bulk acoustic waveforms where the laser beam was directed onto free metal surfaces in the presence and absence of surface plasmas, and onto modified metal surfaces. The application of acoustic wave propagation theory has allowed theoretical waveforms to be determined. By combining data for thermoelastic and normal force sources, waveforms have been produced that follow closely those measured experimentally.