Small-scale soft robots demonstrate intricate life-like behavior and allow navigation through arduous terrains and confined spaces. However, the primary challenges in soft robotics are 1) creating actuators capable of quick, reversible 22D-to-3D shape morphing with adjustable stiffness, 2) improving actuation force and robustness for wider applications, and 3) designing holistic systems for untethered manipulation and flexible multimodality in practical scenarios. Here, mechanically compliant paper-like robots are presented with multiple functionalities. The robots are based on photothermally activated polymer bimorph actuators that incorporate graphene for the photo-thermal conversion of energy and muscovite mica, with its high Young's modulus, providing the required stiffness. Conversion of light into heat leads to thermal expansion and bending of the stress-mismatched structures. The actuators are designed on the basis of a modified Timoshenko model, and numerical simulations are employed to evaluate their actuation performance. The membranes can be utilized for light-driven programmable shape-morphing. Localized control allows the implementation of active hinges at arbitrary positions within the membrane. Integrated into small-scale soft robots in mass production, the membrane facilitates locomotion, rolling, and flipping of the robots. Further, grasping and kicking mechanisms are demonstrated, highlighting the potential of such actuators for future applications. Light is a potential power source for small-scale robotic systems. This work presents a graphene-mica-based photo-thermal actuator for small-scale soft robots, allowing actuation at high speeds with large curvature changes. A comprehensive model for the design is presented and the fundamental properties of the actuator are described and compared to the state-of-the-art. Further, integration of the actuator into various applications is demonstrated. image

Fish locomotion is enabled by fin rays-actively deformable boney rods, which manipulate the fin to facilitate complex interaction with surrounding water and enable propulsion. Replicating the performance and kinematics of the biological fin ray from an engineering perspective is a challenging task and has not been realised thus far. This work introduces a prototype of a fin ray-inspired origami electromagnetic tendon-driven (FOLD) actuator, designed to emulate the functional dynamics of fish fin rays. Constructed in minutes using origami/kirigami and paper joinery techniques from flat laser-cut polypropylene film, this actuator is low-cost at 0.80 ($1), simple to assemble, and durable for over one million cycles. We leverage its small size to embed eight into two fin membranes of a 135 mm long cuttlefish robot capable of four degrees of freedom swimming. We present an extensive kinematic and swimming parametric study with 1015 data points from 7.6 hours of video, which has been used to determine optimal kinematic parameters and validate theoretical constants observed in aquatic animals. Notably, the study explores the nuanced interplay between undulation patterns, power distribution, and locomotion efficiency, underscoring the potential of the actuator as a model system for the investigation of energy-efficient propulsion and control of bioinspired systems. The versatility of the actuator is further demonstrated by its integration into a fish and a jellyfish.

Various applications require multi-channel high-voltage sources for their control, e.g. electrostatic adhesion, electrophoresis and artificial muscles such as piezoelectric, hydraulically amplified self-healing electrostatic(HASEL) and dielectric elastomer actuators(DEAs). Further, the ability to simultaneously monitor the state of the actuators either with images, or voltage and current sensing is crucial to characterise their behaviour. In this work, we present the design of a versatile characterisation setup, capable of generating eight HV (15 kV) arbitrary waveforms(rise time of 8 ms and fall time of 80 ms for 60 MΩ load), while synchronously monitoring voltage and current, and record high-speed (120 fps) video. The setup ensures modularity and customisability by consisting of three independent modules: (1) The imaging module includes a Raspberry Pi and a Pi Camera; (2) A 3.3 V analogue interface 16-bit resolution data acquisition module on a PCB that accommodates a microcontroller board, two 8-channel analogue-to-digital converters, and an 8-channel digital-to-analogue converter; (3) Up to 8 DC-to-HVDC converter boards powered by 12 V DC, with 3.3 V analogue interface.

Energy sustainability poses a great challenge in miniaturised soft robotics. Light, as renewable and clean energy, is promising to power, actuate and control such robots. However, efficient, high-speed and high-power actuators operating on light-provided power are still in their infancy and subject to intensive research. Here, we demonstrate photo-thermal bimorph actuators based on polydimethylsiloxane (PDMS), graphene (G), and muscovite mica. The PDMS/G/Mica photo-thermal actuator converts light efficiently to displacement and force. Under illumination, the PDMS/G/Mica actuators achieve a large curvature change of 0.76 mm -1 at moderate light intensities of 150 mW/cm 2 , beyond that of most photo-thermal actuators reported in the literature so far. The actuators are further integrated into bio-inspired, photo-responsive soft robotic structures such as flower petals and inchworms to demonstrate their suitability for various future applications.

The design of efficient graphene-silicon (GSi) Schottky junction photodetectors requires detailed understanding of the spatial origin of the photoresponse. Scanning-photocurrent-microscopy (SPM) studies have been carried out in the visible wavelengths regions only, in which the response due to silicon is dominant. Here we present comparative SPM studies in the visible ($\lambda$ = 633nm) and infrared ($\lambda$ = 1550nm) wavelength regions for a number of GSi Schottky junction photodetector architectures, revealing the photoresponse mechanisms for silicon and graphene dominated responses, respectively, and demonstrating the influence of electrostatics on the device performance. Local electric field enhancement at the graphene edges leads to a more than ten-fold increased photoresponse compared to the bulk of the graphene-silicon junction. Intentional design and patterning of such graphene edges is demonstrated as an efficient strategy to increase the overall photoresponse of the devices. Complementary simulations and modeling illuminate observed effects and highlight the importance of considering graphene's shape and pattern and device geometry in the device design.

Graphene–silicon-on-insulator (GSOI) photodetectors for high-speed free space light detection.

Detection of light in the near- and short-wave infrared spectral region is of great interest for applications ranging from imaging to sensing. However, silicon commonly employed for photodetectors is limited in its spectral range to wavelengths of 400… 1100nm due to its band gap of $\sim$1.1eV. Materials for light detection in the wavelength range $\gt1100$ nm are typically III-V-based semiconductors such as e.g. InGaAs which are difficult to integrate with CMOS technology, hindering use in main-stream applications due to technical issues and associated high cost. Here, we present graphene-silicon hybrid structure photodetectors which demonstrate an extended spectral detection range from $\sim$400… 1700nm.

Graphene-silicon Schottky diode photodetectors possess beneficial properties such as high responsivities and detectivities, broad spectral wavelength operation and high operating speeds. Various routes and architectures have been employed in the past to fabricate devices. Devices are commonly based on the removal of the silicon-oxide layer on the surface of silicon by wet-etching before deposition of graphene on top of silicon to form the graphene-silicon Schottky junction. In this work, we systematically investigate the influence of the interfacial oxide layer, the fabrication technique employed and the silicon substrate on the light detection capabilities of graphene-silicon Schottky diode photodetectors. The properties of devices are investigated over a broad wavelength range from near-UV to short-/mid-infrared radiation, radiation intensities covering over five orders of magnitude as well as the suitability of devices for high speed operation. Results show that the interfacial layer, depending on the required application, is in fact beneficial to enhance the photodetection properties of such devices. Further, we demonstrate the influence of the silicon substrate on the spectral response and operating speed. Fabricated devices operate over a broad spectral wavelength range from the near-UV to the short-/mid-infrared (thermal) wavelength regime, exhibit high photovoltage responses approaching 106 V W-1 and short rise- and fall-times of tens of nanoseconds.

In solids, high harmonic radiation arises from the subcycle dynamics of electrons and holes under the action of an intense laser field. The strong-field regime opens new opportunities to understand and control carrier dynamics on ultrafast time scales, including the coherent dynamics of quasiparticles such as massless Dirac fermions. Here, we irradiate monolayer and few-layer graphene with intense infrared light to produce nonperturbative harmonics of the fundamental up to the seventh order. We find that the polarization dependence shows surprising agreement with gas-phase harmonics. Using a two-band model, we explore the nonlinear current due to electrons near the Dirac points, and we discuss the interplay between intraband and interband contributions to the harmonic spectrum. This interplay opens new opportunities to access ultrafast and strong-field physics of graphene.

The combination of plasmonic nanoparticles and graphene enhances the responsivity and spectral selectivity of graphene-based photodetectors. However, the small area of the metal-graphene junction, where the induced-electron hole pairs separate, limits the photoactive region to submicron length scales. Here, we couple graphene with a plasmonic grating and exploit the resulting surface plasmon polaritons to deliver the collected photons to the junction region of a metal-graphene-metal photodetector. This gives a 400% enhancement of responsivity and a 1000% increase in photoactive length, combined with tunable spectral selectivity. The interference between surface plasmon polaritons and the incident wave introduces new functionalities, such as light flux attraction or repulsion from the contact edges, enabling the tailored design of the photodetector's spectral response. This architecture can also be used for surface plasmon biosensing with direct-electric-redout, eliminating the need of bulky optics.

Graphene's high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal-graphene-metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo- and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.

We present electron-beam-induced oxidation of single- and bilayer graphene devices in a low-voltage scanning electron microscope. We show that the injection of oxygen leads to targeted etching at the focal point, enabling us to pattern graphene with a resolution of better than 20nm. Voltage-contrast imaging, in conjunction with finite-element simulations, explain the secondary-electron intensities and correlate them to the etch profile.

An apparatus comprising first and second layers of electrically conductive material (304, 307) separated by a layer of electrically insulating material (306), wherein one or both layers of electrically conductive material (304, 307) comprise graphene, and wherein the apparatus is configured such that electrons are able to tunnel from the first layer of electrically conductive material (304) through the layer of electrically insulating material (306) to the second layer of electrically conductive material (307).